diff --git a/apps/decoder.c b/apps/decoder.c
index ed96f7919618ff1fc2c47531da14f77b5b81b8de..4feea3fcfd1d70e937c9f610c2bede86748b809c 100644
--- a/apps/decoder.c
+++ b/apps/decoder.c
@@ -150,6 +150,9 @@ typedef struct
     uint16_t directivityPatternId[IVAS_MAX_NUM_OBJECTS];
     bool objEditEnabled;
     char *objEditFileName;
+#ifdef FIX_1419_MONO_STEREO_UMX
+    bool evsMode;
+#endif
 
 } DecArguments;
 
@@ -961,6 +964,9 @@ static bool parseCmdlIVAS_dec(
     arg->output_Fs = IVAS_MAX_SAMPLING_RATE;
     arg->outputConfig = IVAS_AUDIO_CONFIG_MONO;
     arg->decMode = IVAS_DEC_MODE_IVAS;
+#ifdef FIX_1419_MONO_STEREO_UMX
+    arg->evsMode = false;
+#endif
     arg->quietModeEnabled = false;
     arg->delayCompensationEnabled = true;
     arg->voipMode = false;
@@ -1502,6 +1508,14 @@ static bool parseCmdlIVAS_dec(
             }
             i++;
         }
+#ifdef FIX_1419_MONO_STEREO_UMX
+        else if ( strcmp( argv_to_upper, "-EVS" ) == 0 )
+        {
+            arg->evsMode = true;
+            arg->decMode = IVAS_DEC_MODE_EVS;
+            i++;
+        }
+#endif
 
         /*-----------------------------------------------------------------*
          * Option not recognized
@@ -1644,6 +1658,9 @@ static bool parseCmdlIVAS_dec(
 static void usage_dec( void )
 {
     fprintf( stdout, "Usage for EVS:   IVAS_dec.exe [Options] Fs bitstream_file output_file\n" );
+#ifdef FIX_1419_MONO_STEREO_UMX
+    fprintf( stdout, "                 OR usage for IVAS (below) with -evs option and OutputConf\n" );
+#endif
     fprintf( stdout, "Usage for IVAS:  IVAS_dec.exe [Options] OutputConf Fs bitstream_file output_file\n\n" );
 
     fprintf( stdout, "Mandatory parameters:\n" );
@@ -1660,6 +1677,9 @@ static void usage_dec( void )
 
     fprintf( stdout, "Options:\n" );
     fprintf( stdout, "--------\n" );
+#ifdef FIX_1419_MONO_STEREO_UMX
+    fprintf( stdout, "-evs                : Specify EVS mode for supplied bitstream\n" );
+#endif
     fprintf( stdout, "-VOIP               : VoIP mode: RTP in G192\n" );
     fprintf( stdout, "-VOIP_hf_only=0     : VoIP mode: EVS RTP Payload Format hf_only=0 in rtpdump\n" );
 #ifdef IVAS_RTPDUMP
diff --git a/lib_com/common_api_types.h b/lib_com/common_api_types.h
index 80c90d6b3152a5ace3ef0f0f205ac0c61784a356..18a0aea9f631b3d3a35f489eedbdfc68e66a233b 100644
--- a/lib_com/common_api_types.h
+++ b/lib_com/common_api_types.h
@@ -222,6 +222,18 @@ typedef enum _ivas_binaural_renderer_type
     IVAS_BIN_RENDERER_TYPE_DEFAULT,
 
 } IVAS_BIN_RENDERER_TYPE;
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+typedef struct _IVAS_MS_UMX_CONF_DATA
+{
+    int16_t spatialEnabled; /* internal flag for spatial rendering */
+    int16_t stereoLR;       /* internal flag to use ±90 for BRIRs */
+    float radius;
+    float azi[2];
+    float ele[2];
+
+} IVAS_MS_UMX_CONF_DATA, *IVAS_MS_UMX_CONF_HANDLE;
+#endif
 
 /*----------------------------------------------------------------------------------*
  * Split rendering API constants, structures, and enums
@@ -335,6 +347,9 @@ typedef struct _IVAS_RENDER_CONFIG
 #endif
     IVAS_ROOM_ACOUSTICS_CONFIG_DATA roomAcoustics;
     ISAR_SPLIT_REND_CONFIG_DATA split_rend_config;
+#ifdef FIX_1419_MONO_STEREO_UMX
+    IVAS_MS_UMX_CONF_DATA mono_stereo_upmix_config;
+#endif
     float directivity[IVAS_MAX_NUM_OBJECTS * 3];
     float distAtt[3];
 
diff --git a/lib_com/ivas_cnst.h b/lib_com/ivas_cnst.h
index 3e8521f47d8f5fc485771b6c1ce76bfaffcf783d..c169b7684ad9688c7624a8bbd49a97a637221bb9 100755
--- a/lib_com/ivas_cnst.h
+++ b/lib_com/ivas_cnst.h
@@ -1251,7 +1251,11 @@ typedef enum
  *----------------------------------------------------------------------------------*/
 
 #define MC_LS_SETUP_BITS                        3                           /* number of bits for writing the MC LS configuration */
+#ifdef FIX_1419_MONO_STEREO_UMX
+#define LS_SETUP_CONVERSION_NUM_MAPPINGS        41                          /* number of mappings for LS setup conversion         */
+#else
 #define LS_SETUP_CONVERSION_NUM_MAPPINGS        35                          /* number of mappings for LS setup conversion         */
+#endif
 
 typedef enum
 {
diff --git a/lib_com/options.h b/lib_com/options.h
index b72be74b4f342769a8b21a0bde86c3029b833403..124f59632fddfae8e6253ffed72a5a9b13c825ea 100755
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -170,6 +170,7 @@
 #define TMP_1342_WORKAROUND_DEC_FLUSH_BROKEN_IN_SR      /* FhG: Temporary workaround for incorrect implementation of decoder flush with split rendering */
 #define FIX_1413_IGF_INIT_PRINTOUT                      /* FhG: use correct variable for IGF initiliazation */
 #define RENDERER_MD_SYNC_DELAY_TO_INTEGER               /* FhG: change data type of metadata sync delay in ext renderer to int16_t for better BASOP portability (and nicer code) */
+#define FIX_1419_MONO_STEREO_UMX                        /* FhG: fix for issue 1418 : support upmix to all output formats for mono and stereo */
 
 
 /* #################### End BE switches ################################## */
diff --git a/lib_dec/ivas_init_dec.c b/lib_dec/ivas_init_dec.c
index 80b8c7e5e961c7713b4de1e009490e5fe82e7b40..7b4f178239963236a198721981b721443b79cbb0 100644
--- a/lib_dec/ivas_init_dec.c
+++ b/lib_dec/ivas_init_dec.c
@@ -1279,7 +1279,15 @@ ivas_error ivas_init_decoder(
 
     if ( output_config == IVAS_AUDIO_CONFIG_EXTERNAL )
     {
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( st_ivas->ivas_format == MONO_FORMAT )
+        {
+            hDecoderConfig->nchan_out = 1;
+        }
+        else if ( st_ivas->ivas_format == STEREO_FORMAT )
+#else
         if ( st_ivas->ivas_format == STEREO_FORMAT )
+#endif
         {
             hDecoderConfig->nchan_out = CPE_CHANNELS;
         }
@@ -1332,12 +1340,30 @@ ivas_error ivas_init_decoder(
         st_ivas->hOutSetup.output_config = st_ivas->intern_config;
         st_ivas->hOutSetup.nchan_out_woLFE = audioCfg2channels( st_ivas->intern_config );
     }
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+    if ( st_ivas->ivas_format == MONO_FORMAT || st_ivas->ivas_format == STEREO_FORMAT )
+    {
+        st_ivas->transport_config = ( st_ivas->ivas_format == MONO_FORMAT ) ? IVAS_AUDIO_CONFIG_MONO : IVAS_AUDIO_CONFIG_STEREO;
+    }
+#endif
 
     /* Only initialize transport setup if it is used */
     if ( st_ivas->transport_config != IVAS_AUDIO_CONFIG_INVALID )
     {
         ivas_output_init( &( st_ivas->hTransSetup ), st_ivas->transport_config );
     }
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+    /* Override transport config values from render config */
+    if ( ( st_ivas->ivas_format == MONO_FORMAT || st_ivas->ivas_format == STEREO_FORMAT ) &&
+         st_ivas->hRenderConfig != NULL &&
+         st_ivas->hRenderConfig->mono_stereo_upmix_config.spatialEnabled )
+    {
+        st_ivas->hTransSetup.ls_azimuth = st_ivas->hRenderConfig->mono_stereo_upmix_config.azi;
+        st_ivas->hTransSetup.ls_elevation = st_ivas->hRenderConfig->mono_stereo_upmix_config.ele;
+    }
+#endif
 
     if ( st_ivas->ivas_format == MC_FORMAT && st_ivas->mc_mode == MC_MODE_MCMASA )
     {
@@ -1414,7 +1440,9 @@ ivas_error ivas_init_decoder(
     else if ( st_ivas->ivas_format == STEREO_FORMAT )
     {
         st_ivas->nchan_transport = CPE_CHANNELS;
+#ifndef FIX_1419_MONO_STEREO_UMX /* already set now by renderer_select() */
         st_ivas->intern_config = IVAS_AUDIO_CONFIG_STEREO;
+#endif
 
         st_ivas->nSCE = 0;
         st_ivas->nCPE = 1; /* in stereo, there is always only one CPE */
@@ -2148,7 +2176,13 @@ ivas_error ivas_init_decoder(
     }
     else if ( st_ivas->renderer_type == RENDERER_BINAURAL_MIXER_CONV || st_ivas->renderer_type == RENDERER_BINAURAL_MIXER_CONV_ROOM )
     {
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( ( st_ivas->hDecoderConfig->Opt_Headrotation || st_ivas->hDecoderConfig->Opt_ExternalOrientation ) &&
+             ( ( st_ivas->ivas_format == MONO_FORMAT || st_ivas->ivas_format == STEREO_FORMAT ) ||
+               ( st_ivas->renderer_type == RENDERER_BINAURAL_MIXER_CONV_ROOM && st_ivas->ivas_format == MC_FORMAT ) ) )
+#else
         if ( st_ivas->renderer_type == RENDERER_BINAURAL_MIXER_CONV_ROOM && st_ivas->ivas_format == MC_FORMAT && ( st_ivas->hDecoderConfig->Opt_Headrotation || st_ivas->hDecoderConfig->Opt_ExternalOrientation ) )
+#endif
         {
             if ( ( error = efap_init_data( &( st_ivas->hEFAPdata ), st_ivas->hIntSetup.ls_azimuth, st_ivas->hIntSetup.ls_elevation, st_ivas->hIntSetup.nchan_out_woLFE, EFAP_MODE_EFAP ) ) != IVAS_ERR_OK )
             {
@@ -2304,7 +2338,8 @@ ivas_error ivas_init_decoder(
     }
 
     /*-----------------------------------------------------------------*
-     * LFE handles for rendering after rendering to adjust LFE delay to filter delay
+     * LFE handles for rendering after rendering to adjust LFE delay to
+     * filter delay
      *-----------------------------------------------------------------*/
 
     if ( st_ivas->mc_mode == MC_MODE_MCT || st_ivas->mc_mode == MC_MODE_PARAMUPMIX )
@@ -3136,6 +3171,7 @@ static ivas_error doSanityChecks_IVAS(
         return IVAS_ERROR( IVAS_ERR_INVALID_OUTPUT_FORMAT, "Error: Non-diegetic panning not supported in this IVAS format" );
     }
 
+#ifndef FIX_1419_MONO_STEREO_UMX /* we now support basically everything for stereo */
     /* Verify stereo output configuration */
     if ( st_ivas->ivas_format == STEREO_FORMAT )
     {
@@ -3148,10 +3184,21 @@ static ivas_error doSanityChecks_IVAS(
     else
     {
         if ( output_config == IVAS_AUDIO_CONFIG_INVALID )
+#else /* exclude invalid configs instead of matching valid ones */
+    if ( output_config == IVAS_AUDIO_CONFIG_INVALID ||
+         output_config == IVAS_AUDIO_CONFIG_ISM1 ||
+         output_config == IVAS_AUDIO_CONFIG_ISM2 ||
+         output_config == IVAS_AUDIO_CONFIG_ISM3 ||
+         output_config == IVAS_AUDIO_CONFIG_ISM4 ||
+         output_config == IVAS_AUDIO_CONFIG_MASA1 ||
+         output_config == IVAS_AUDIO_CONFIG_MASA2 )
+#endif
         {
             return IVAS_ERROR( IVAS_ERR_INVALID_OUTPUT_FORMAT, "Incorrect output configuration specified!" );
         }
+#ifndef FIX_1419_MONO_STEREO_UMX
     }
+#endif
 
     if ( ( output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_CODED || output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_PCM ) && output_Fs != 48000 )
     {
diff --git a/lib_dec/ivas_jbm_dec.c b/lib_dec/ivas_jbm_dec.c
index b19f0bdf7ecfc2b2729a803959e96120c27bc967..c97e5ff64783cba4f46ba1cca6336886f4d63f73 100644
--- a/lib_dec/ivas_jbm_dec.c
+++ b/lib_dec/ivas_jbm_dec.c
@@ -934,14 +934,90 @@ ivas_error ivas_jbm_dec_render(
     {
         ivas_jbm_dec_tc_buffer_playout( st_ivas, nSamplesAskedLocal, nSamplesRendered, p_output );
     }
+#ifdef FIX_1419_MONO_STEREO_UMX
+    else if ( st_ivas->ivas_format == MONO_FORMAT || st_ivas->ivas_format == STEREO_FORMAT )
+#else
     else if ( st_ivas->ivas_format == STEREO_FORMAT )
+#endif
     {
+#ifdef FIX_1419_MONO_STEREO_UMX
+        *nSamplesRendered = min( st_ivas->hTcBuffer->n_samples_available, nSamplesAskedLocal );
+#endif
+
         /* Rendering */
         if ( st_ivas->renderer_type == RENDERER_MC )
         {
+#ifndef FIX_1419_MONO_STEREO_UMX
             *nSamplesRendered = min( st_ivas->hTcBuffer->n_samples_available, nSamplesAskedLocal );
+#endif
             ivas_ls_setup_conversion( st_ivas, st_ivas->nchan_transport, *nSamplesRendered, p_tc, p_output );
         }
+#ifdef FIX_1419_MONO_STEREO_UMX
+        else if ( st_ivas->renderer_type == RENDERER_SBA_LINEAR_ENC )
+        {
+            if ( st_ivas->ivas_format == MONO_FORMAT )
+            {
+                /* routed to W */
+                ivas_jbm_dec_tc_buffer_playout( st_ivas, nSamplesAskedLocal, nSamplesRendered, p_output );
+            }
+            else if ( st_ivas->ivas_format == STEREO_FORMAT )
+            {
+                for ( n = 0; n < *nSamplesRendered; n++ )
+                {
+                    p_output[0][n] = 0.5f * ( p_output[0][n] + p_output[1][n] ); /* W = 0.5 * ( L + R ) */
+                    p_output[1][n] = 0.5f * ( p_output[0][n] - p_output[1][n] ); /* Y = 0.5 * ( L - R ) */
+                }
+            }
+        }
+        else if ( st_ivas->renderer_type == RENDERER_BINAURAL_OBJECTS_TD )
+        {
+            /* Rendering for BINAURAL, BINAURAL_ROOM_REVERB and split rendering */
+            if ( output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_CODED || output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_PCM )
+            {
+                if ( ( error = ivas_td_binaural_renderer_sf_splitBinaural( st_ivas, p_output, *nSamplesRendered ) ) != IVAS_ERR_OK )
+                {
+                    return error;
+                }
+            }
+            else
+            {
+                if ( ( error = ivas_td_binaural_renderer_sf( st_ivas, p_output, *nSamplesRendered ) ) != IVAS_ERR_OK )
+                {
+                    return error;
+                }
+            }
+        }
+        else if ( st_ivas->renderer_type == RENDERER_BINAURAL_MIXER_CONV_ROOM )
+        {
+            /* Rendering for BINAURAL_ROOM_IR */
+            if ( st_ivas->hDecoderConfig->Opt_Headrotation && st_ivas->ivas_format == MONO_FORMAT )
+            {
+                /* Since rotation is performed on 7.1+4, we treat mono as 7.1+4 with other channels zero
+                 * so move the mono content in index 0 to index 2 (center channel) */
+                float *tmp;
+                tmp = p_output[2];
+                p_output[2] = p_output[0];
+                p_output[0] = tmp;
+            }
+
+            if ( ( error = ivas_rend_crendProcessSubframe( st_ivas->hCrendWrapper,
+                                                           st_ivas->intern_config,
+                                                           st_ivas->hOutSetup.output_config,
+                                                           st_ivas->hDecoderConfig,
+                                                           st_ivas->hCombinedOrientationData,
+                                                           &st_ivas->hIntSetup,
+                                                           st_ivas->hEFAPdata,
+                                                           st_ivas->hTcBuffer,
+                                                           p_output,
+                                                           p_output,
+                                                           *nSamplesRendered,
+                                                           output_Fs,
+                                                           0 ) ) != IVAS_ERR_OK )
+            {
+                return error;
+            }
+        }
+#endif
     }
     else if ( st_ivas->ivas_format == ISM_FORMAT )
     {
@@ -1928,11 +2004,15 @@ int16_t ivas_jbm_dec_get_num_tc_channels(
 
     ivas_total_brate = st_ivas->hDecoderConfig->ivas_total_brate;
 
+#ifndef FIX_1419_MONO_STEREO_UMX /* since we support more output formats for mono, this is no longer sensible; leave it at the default from above */
     if ( st_ivas->ivas_format == MONO_FORMAT )
     {
         num_tc = st_ivas->hDecoderConfig->nchan_out;
     }
     else if ( st_ivas->ivas_format == STEREO_FORMAT && st_ivas->hDecoderConfig->nchan_out == 1 )
+#else
+    if ( st_ivas->ivas_format == STEREO_FORMAT && st_ivas->hDecoderConfig->nchan_out == 1 )
+#endif
     {
         num_tc = 1;
     }
@@ -2800,7 +2880,11 @@ void ivas_dec_prepare_renderer(
             ivas_omasa_gain_masa_tc( st_ivas->hTcBuffer->tc, st_ivas->hMasaIsmData->gain_masa_edited, st_ivas->nchan_ism, st_ivas->hTcBuffer->n_samples_available );
         }
     }
+#ifdef FIX_1419_MONO_STEREO_UMX
+    else if ( st_ivas->ivas_format == MONO_FORMAT || st_ivas->ivas_format == STEREO_FORMAT )
+#else
     else if ( st_ivas->ivas_format == STEREO_FORMAT )
+#endif
     {
         ivas_jbm_dec_td_renderers_adapt_subframes( st_ivas );
     }
diff --git a/lib_dec/ivas_objectRenderer_internal.c b/lib_dec/ivas_objectRenderer_internal.c
index ff47b1b9a77fa56f539ca737a201d2fff16f22b5..395d0f599783fae74161a4b385cdbbd5b72f30a9 100644
--- a/lib_dec/ivas_objectRenderer_internal.c
+++ b/lib_dec/ivas_objectRenderer_internal.c
@@ -66,8 +66,22 @@ ivas_error ivas_td_binaural_open(
         return IVAS_ERROR( IVAS_ERR_INTERNAL, "HRTF binary file present but not used in TD renderer" );
     }
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+    return ivas_td_binaural_open_unwrap( &st_ivas->hHrtfTD,
+                                         st_ivas->hDecoderConfig->output_Fs,
+                                         num_src,
+                                         st_ivas->ivas_format,
+                                         st_ivas->transport_config,
+                                         st_ivas->hRenderConfig->directivity,
+                                         st_ivas->hRenderConfig->distAtt,
+                                         ( st_ivas->hRenderConfig != NULL ) ? &st_ivas->hRenderConfig->mono_stereo_upmix_config.radius : NULL,
+                                         st_ivas->hTransSetup,
+                                         &st_ivas->hBinRendererTd,
+                                         &st_ivas->binaural_latency_ns );
+#else
     return ivas_td_binaural_open_unwrap( &st_ivas->hHrtfTD, st_ivas->hDecoderConfig->output_Fs, num_src, st_ivas->ivas_format,
                                          st_ivas->transport_config, st_ivas->hRenderConfig->directivity, st_ivas->hRenderConfig->distAtt, st_ivas->hTransSetup, &st_ivas->hBinRendererTd, &st_ivas->binaural_latency_ns );
+#endif
 }
 
 
@@ -312,6 +326,9 @@ ivas_error ivas_td_binaural_renderer_sf_splitBinaural(
                                                      st_ivas->transport_config,
                                                      st_ivas->hRenderConfig->directivity,
                                                      st_ivas->hRenderConfig->distAtt,
+#ifdef FIX_1419_MONO_STEREO_UMX
+                                                     ( st_ivas->hRenderConfig != NULL ) ? &st_ivas->hRenderConfig->mono_stereo_upmix_config.radius : NULL,
+#endif
                                                      st_ivas->hTransSetup,
                                                      &st_ivas->hTdRendHandles[i],
                                                      &st_ivas->binaural_latency_ns ) ) != IVAS_ERR_OK )
diff --git a/lib_dec/ivas_output_config.c b/lib_dec/ivas_output_config.c
index 17ce37c4d454239048bca6305d2f19337b12a030..14dd3e4942321cb31a296ee9ca2b519617341e0e 100644
--- a/lib_dec/ivas_output_config.c
+++ b/lib_dec/ivas_output_config.c
@@ -41,6 +41,49 @@
 #endif
 #include "wmc_auto.h"
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+static void ms_bin_upmix_renderer_select(
+    const IVAS_FORMAT ivas_format,                 /* i  : Decoder format                             */
+    const IVAS_AUDIO_CONFIG output_config,         /* i  : Decoder output configuration               */
+    const IVAS_MS_UMX_CONF_HANDLE pMsUpmix_config, /* i  : Mono/stereo upmix rendering configuration  */
+    const bool headrotation_enabled,               /* i  : Flag to signal headrotation is enabled     */
+    IVAS_AUDIO_CONFIG *internal_config,            /* o  : Internal configuration for rendering       */
+    RENDERER_TYPE *renderer_type                   /* o  : Selected renderer type                     */
+)
+{
+
+    *internal_config = ( ivas_format == MONO_FORMAT ) ? IVAS_AUDIO_CONFIG_MONO : IVAS_AUDIO_CONFIG_STEREO;
+
+    /* spatial rendering disabled */
+    if ( !pMsUpmix_config->spatialEnabled )
+    {
+        if ( ivas_format == MONO_FORMAT )
+        {
+            *renderer_type = RENDERER_NON_DIEGETIC_DOWNMIX;
+        }
+        else
+        {
+            *renderer_type = RENDERER_DISABLE;
+        }
+        return;
+    }
+
+    /* spatial rendering configuration */
+    if ( output_config == IVAS_AUDIO_CONFIG_BINAURAL_ROOM_IR )
+    {
+        if ( headrotation_enabled )
+        {
+            *internal_config = IVAS_AUDIO_CONFIG_7_1_4;
+        }
+        *renderer_type = RENDERER_BINAURAL_MIXER_CONV_ROOM;
+    }
+    else /* HRIR based formats and split rendering */
+    {
+        *renderer_type = RENDERER_BINAURAL_OBJECTS_TD;
+    }
+}
+#endif
 
 /*-------------------------------------------------------------------------*
  * ivas_renderer_select()
@@ -78,7 +121,20 @@ void ivas_renderer_select(
 
     if ( output_config == IVAS_AUDIO_CONFIG_BINAURAL || output_config == IVAS_AUDIO_CONFIG_BINAURAL_ROOM_IR || output_config == IVAS_AUDIO_CONFIG_BINAURAL_ROOM_REVERB || output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_CODED || output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_PCM )
     {
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( st_ivas->ivas_format == MONO_FORMAT || st_ivas->ivas_format == STEREO_FORMAT )
+        {
+            ms_bin_upmix_renderer_select( st_ivas->ivas_format,
+                                          output_config,
+                                          &st_ivas->hRenderConfig->mono_stereo_upmix_config,
+                                          ( st_ivas->hDecoderConfig->Opt_Headrotation || st_ivas->hDecoderConfig->Opt_ExternalOrientation ),
+                                          internal_config,
+                                          renderer_type );
+        }
+        else if ( st_ivas->ivas_format == ISM_FORMAT )
+#else
         if ( st_ivas->ivas_format == ISM_FORMAT )
+#endif
         {
             if ( st_ivas->ism_mode == ISM_MODE_PARAM )
             {
@@ -236,6 +292,45 @@ void ivas_renderer_select(
      * Non-binaural rendering configurations
      *-----------------------------------------------------------------*/
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+    else if ( st_ivas->ivas_format == MONO_FORMAT || st_ivas->ivas_format == STEREO_FORMAT )
+    {
+        *internal_config = ( st_ivas->ivas_format == MONO_FORMAT ) ? IVAS_AUDIO_CONFIG_MONO : IVAS_AUDIO_CONFIG_STEREO;
+        switch ( output_config )
+        {
+            case IVAS_AUDIO_CONFIG_FOA:
+            case IVAS_AUDIO_CONFIG_HOA2:
+            case IVAS_AUDIO_CONFIG_HOA3:
+                *renderer_type = RENDERER_SBA_LINEAR_ENC;
+                break;
+            case IVAS_AUDIO_CONFIG_5_1:
+            case IVAS_AUDIO_CONFIG_7_1:
+            case IVAS_AUDIO_CONFIG_5_1_2:
+            case IVAS_AUDIO_CONFIG_5_1_4:
+            case IVAS_AUDIO_CONFIG_7_1_4:
+            case IVAS_AUDIO_CONFIG_LS_CUSTOM:
+                *renderer_type = RENDERER_MC;
+                break;
+            case IVAS_AUDIO_CONFIG_MONO:
+                if ( *internal_config == IVAS_AUDIO_CONFIG_STEREO )
+                {
+                    /* stereo to mono downmix */
+                    *renderer_type = RENDERER_MC;
+                }
+                break;
+            case IVAS_AUDIO_CONFIG_STEREO:
+                if ( *internal_config == IVAS_AUDIO_CONFIG_MONO )
+                {
+                    /* mono to stereo upmix */
+                    *renderer_type = RENDERER_NON_DIEGETIC_DOWNMIX;
+                }
+                break;
+            default:
+                /* RENDERER_DISABLE already set by default */
+                break;
+        }
+    }
+#else
     else if ( st_ivas->ivas_format == MONO_FORMAT )
     {
         if ( output_config == IVAS_AUDIO_CONFIG_STEREO )
@@ -250,6 +345,7 @@ void ivas_renderer_select(
             *renderer_type = RENDERER_MC;
         }
     }
+#endif
     else if ( st_ivas->ivas_format == ISM_FORMAT )
     {
         if ( ( output_config == IVAS_AUDIO_CONFIG_STEREO ) && ( st_ivas->hDecoderConfig->Opt_non_diegetic_pan ) )
diff --git a/lib_dec/lib_dec.c b/lib_dec/lib_dec.c
index fc63961eda08cc6e81624ab2d2bb6d13171749ad..17fbdc9c1be4d9149954d6147e88af7db18ef0c9 100644
--- a/lib_dec/lib_dec.c
+++ b/lib_dec/lib_dec.c
@@ -474,8 +474,19 @@ ivas_error IVAS_DEC_Configure(
         return IVAS_ERR_WRONG_PARAMS;
     }
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+    if ( hIvasDec->mode == IVAS_DEC_MODE_EVS &&
+         ( outputConfig == IVAS_AUDIO_CONFIG_INVALID ||
+           outputConfig == IVAS_AUDIO_CONFIG_ISM1 ||
+           outputConfig == IVAS_AUDIO_CONFIG_ISM2 ||
+           outputConfig == IVAS_AUDIO_CONFIG_ISM3 ||
+           outputConfig == IVAS_AUDIO_CONFIG_ISM4 ||
+           outputConfig == IVAS_AUDIO_CONFIG_MASA1 ||
+           outputConfig == IVAS_AUDIO_CONFIG_MASA2 ) )
+#else /* we now support all output formats, so this validation is redundant */
     if ( hIvasDec->mode == IVAS_DEC_MODE_EVS && !( ( outputConfig == IVAS_AUDIO_CONFIG_MONO && !non_diegetic_pan_enabled ) ||
                                                    ( outputConfig == IVAS_AUDIO_CONFIG_STEREO && non_diegetic_pan_enabled ) ) )
+#endif
     {
         return IVAS_ERR_WRONG_MODE;
     }
@@ -876,6 +887,16 @@ ivas_error IVAS_DEC_FeedFrame_Serial(
         {
             hIvasDec->st_ivas->hDecoderConfig->ivas_total_brate = ACELP_8k00;
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+            if ( hIvasDec->st_ivas->hDecoderConfig->output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_CODED ||
+                 hIvasDec->st_ivas->hDecoderConfig->output_config == IVAS_AUDIO_CONFIG_BINAURAL_SPLIT_PCM )
+            {
+                /* necessary to set up correct amount of memory for rendering; remaining setup happens in ivas_dec_setup_all() */
+                ISAR_PRE_REND_GetMultiBinPoseData( &hIvasDec->st_ivas->hRenderConfig->split_rend_config,
+                                                   &hIvasDec->st_ivas->hSplitBinRend->splitrend.multiBinPoseData,
+                                                   ( hIvasDec->st_ivas->hCombinedOrientationData != NULL ) ? hIvasDec->st_ivas->hCombinedOrientationData->sr_pose_pred_axis : DEFAULT_AXIS );
+            }
+#endif
             if ( ( error = ivas_init_decoder( hIvasDec->st_ivas ) ) != IVAS_ERR_OK )
             {
                 return error;
@@ -1721,6 +1742,10 @@ ivas_error IVAS_DEC_PrepareRenderer(
     IVAS_DEC_HANDLE hIvasDec /* i/o: IVAS decoder handle    */
 )
 {
+#ifdef FIX_1419_MONO_STEREO_UMX
+    ivas_error error;
+
+#endif
     if ( hIvasDec == NULL || hIvasDec->st_ivas == NULL )
     {
         return IVAS_ERR_UNEXPECTED_NULL_POINTER;
@@ -1730,6 +1755,18 @@ ivas_error IVAS_DEC_PrepareRenderer(
     {
         ivas_dec_prepare_renderer( hIvasDec->st_ivas );
     }
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+    if ( hIvasDec->st_ivas->hRenderConfig != NULL )
+    {
+        if ( ( error = ms_upmix_validate_config( &hIvasDec->st_ivas->hRenderConfig->mono_stereo_upmix_config,
+                                                 hIvasDec->st_ivas->ivas_format,
+                                                 hIvasDec->st_ivas->hDecoderConfig->output_config ) ) != IVAS_ERR_OK )
+        {
+            return error;
+        }
+    }
+#endif
 
     hIvasDec->hasBeenPreparedRendering = true;
 
@@ -2349,7 +2386,12 @@ static ivas_error ivas_dec_setup_all(
 {
     ivas_error error;
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+    /* split rendering related functions in else are required also for mono SR */
+    if ( hIvasDec->mode == IVAS_DEC_MODE_EVS && splitRendBits == NULL )
+#else
     if ( hIvasDec->mode == IVAS_DEC_MODE_EVS )
+#endif
     {
         if ( hIvasDec->st_ivas->renderer_type == RENDERER_NON_DIEGETIC_DOWNMIX )
         {
@@ -2387,7 +2429,11 @@ static ivas_error ivas_dec_setup_all(
          * - reconfigure the decoder when the number of TC or IVAS total bitrate change
          *----------------------------------------------------------------*/
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( st_ivas->bfi == 0 && hIvasDec->mode != IVAS_DEC_MODE_EVS )
+#else
         if ( st_ivas->bfi == 0 )
+#endif
         {
             if ( ( error = ivas_dec_setup( st_ivas ) ) != IVAS_ERR_OK )
             {
@@ -3220,6 +3266,11 @@ static ivas_error copyRendererConfigStruct(
     mvr2r( hRCin->roomAcoustics.pAcoustic_dsr, hRCout->roomAcoustics.pAcoustic_dsr, CLDFB_NO_CHANNELS_MAX );
     mvr2r( hRCin->directivity, hRCout->directivity, 3 * MAX_NUM_OBJECTS );
     mvr2r( hRCin->distAtt, hRCout->distAtt, 3 );
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+    /* Mono/Stereo upmix configuration */
+    hRCout->mono_stereo_upmix_config = hRCin->mono_stereo_upmix_config;
+#endif
 
     hRCout->split_rend_config = hRCin->split_rend_config;
 
@@ -3373,6 +3424,28 @@ ivas_error IVAS_DEC_FeedRenderConfig(
 
     mvr2r( renderConfig.directivity, hRenderConfig->directivity, 3 * MAX_NUM_OBJECTS );
     mvr2r( renderConfig.distAtt, hRenderConfig->distAtt, 3 );
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+    /* Mono/Stereo upmix configuration */
+    if ( renderConfig.mono_stereo_upmix_config.spatialEnabled )
+    {
+        /* copy data */
+        hRenderConfig->mono_stereo_upmix_config.spatialEnabled = renderConfig.mono_stereo_upmix_config.spatialEnabled;
+        hRenderConfig->mono_stereo_upmix_config.radius = renderConfig.mono_stereo_upmix_config.radius;
+        hRenderConfig->mono_stereo_upmix_config.stereoLR = renderConfig.mono_stereo_upmix_config.stereoLR;
+
+        mvr2r( renderConfig.mono_stereo_upmix_config.azi, hRenderConfig->mono_stereo_upmix_config.azi, 2 );
+        mvr2r( renderConfig.mono_stereo_upmix_config.ele, hRenderConfig->mono_stereo_upmix_config.ele, 2 );
+
+        /* validate configuration early - repeated in IVAS_DEC_PrepareRenderer when input format is available */
+        if ( ( error = ms_upmix_validate_config( &hRenderConfig->mono_stereo_upmix_config,
+                                                 st_ivas->ivas_format,
+                                                 st_ivas->hDecoderConfig->output_config ) ) != IVAS_ERR_OK )
+        {
+            return error;
+        }
+    }
+#endif
 
     hRenderConfig->split_rend_config = renderConfig.split_rend_config;
 
@@ -4670,7 +4743,11 @@ static ivas_error evs_dec_main(
 {
     DEC_CORE_HANDLE *hCoreCoder;
     float mixer_left, mixer_rigth;
+#ifdef FIX_1419_MONO_STEREO_UMX /* required now that mono can render to a higher number of output channels */
+    float *p_output[MAX_TRANSPORT_CHANNELS];
+#else
     float *p_output[MAX_OUTPUT_CHANNELS_IN_DIEGETIC_PAN];
+#endif
     int16_t ch, nOutSamples;
     ivas_error error;
 
@@ -4680,9 +4757,19 @@ static ivas_error evs_dec_main(
 
     mdct_switching_dec( hCoreCoder[0] );
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+    for ( ch = 0; ch < MAX_TRANSPORT_CHANNELS; ch++ )
+#else
     for ( ch = 0; ch < MAX_OUTPUT_CHANNELS_IN_DIEGETIC_PAN; ch++ )
+#endif
     {
         p_output[ch] = st_ivas->p_output_f[ch];
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( p_output[ch] != NULL )
+        {
+            set_zero( p_output[ch], L_FRAME48k );
+        }
+#endif
     }
 
     /* run the main EVS decoding routine */
diff --git a/lib_rend/ivas_crend.c b/lib_rend/ivas_crend.c
index 91346675023091f478cd4a637e93d0347e1d052e..880f3735ac2e35d66b7cd66f8522181423d834d3 100644
--- a/lib_rend/ivas_crend.c
+++ b/lib_rend/ivas_crend.c
@@ -167,6 +167,9 @@ static ivas_error ivas_rend_initCrend(
     const AUDIO_CONFIG outConfig,
     HRTFS_CREND_HANDLE hHrtfCrend,
     const int16_t ext_rend_flag,
+#ifdef FIX_1419_MONO_STEREO_UMX
+    const int16_t bin_upmix_stereolr_flag,
+#endif
     const int32_t output_Fs )
 {
     int16_t i, j, tmp, tmp2;
@@ -228,8 +231,15 @@ static ivas_error ivas_rend_initCrend(
     {
         if ( inConfigType == IVAS_REND_AUDIO_CONFIG_TYPE_CHANNEL_BASED )
         {
-            hHrtf->max_num_ir -= 1; /* subtract LFE */
-            hHrtf->gain_lfe = GAIN_LFE;
+#ifdef FIX_1419_MONO_STEREO_UMX
+            if ( inConfig != IVAS_AUDIO_CONFIG_MONO && inConfig != IVAS_AUDIO_CONFIG_STEREO )
+            {
+#endif
+                hHrtf->max_num_ir -= 1; /* subtract LFE */
+                hHrtf->gain_lfe = GAIN_LFE;
+#ifdef FIX_1419_MONO_STEREO_UMX
+            }
+#endif
 
             if ( output_Fs == 48000 )
             {
@@ -338,7 +348,20 @@ static ivas_error ivas_rend_initCrend(
 
             for ( i = 0; i < hHrtf->max_num_ir; i++ )
             {
+#ifdef FIX_1419_MONO_STEREO_UMX
+                if ( inConfig == IVAS_AUDIO_CONFIG_MONO )
+                {
+                    tmp = channelIndex_CICP1[i];
+                }
+                else if ( inConfig == IVAS_AUDIO_CONFIG_STEREO )
+                {
+                    /* flag to select ±90 loudspeakers instead of ±30 */
+                    tmp = ( bin_upmix_stereolr_flag ) ? channelIndex_LR[i] : channelIndex_CICP2[i];
+                }
+                else if ( inConfig == IVAS_AUDIO_CONFIG_5_1 )
+#else
                 if ( inConfig == IVAS_AUDIO_CONFIG_5_1 )
+#endif
                 {
                     tmp = channelIndex_CICP6[i];
                 }
@@ -360,7 +383,11 @@ static ivas_error ivas_rend_initCrend(
                 }
                 else
                 {
+#ifdef FIX_1419_MONO_STEREO_UMX
+                    return IVAS_ERROR( IVAS_ERR_INTERNAL_FATAL, "Error: Invalid channel configuration for Crend!\n\n" );
+#else
                     return IVAS_ERROR( IVAS_ERR_INTERNAL_FATAL, "Error: Channel configuration not specified!\n\n" );
+#endif
                 }
 
                 if ( output_Fs == 48000 )
@@ -703,8 +730,15 @@ static ivas_error ivas_rend_initCrend(
     {
         if ( inConfigType == IVAS_REND_AUDIO_CONFIG_TYPE_CHANNEL_BASED )
         {
-            hHrtf->max_num_ir -= 1; /* subtract LFE */
-            hHrtf->gain_lfe = GAIN_LFE;
+#ifdef FIX_1419_MONO_STEREO_UMX
+            if ( inConfig != IVAS_AUDIO_CONFIG_MONO && inConfig != IVAS_AUDIO_CONFIG_STEREO )
+            {
+#endif
+                hHrtf->max_num_ir -= 1; /* subtract LFE */
+                hHrtf->gain_lfe = GAIN_LFE;
+#ifdef FIX_1419_MONO_STEREO_UMX
+            }
+#endif
         }
 
         if ( ext_rend_flag == 1 )
@@ -747,7 +781,20 @@ static ivas_error ivas_rend_initCrend(
 
         for ( i = 0; i < hHrtf->max_num_ir; i++ )
         {
+#ifdef FIX_1419_MONO_STEREO_UMX
+            if ( inConfig == IVAS_AUDIO_CONFIG_MONO )
+            {
+                tmp = channelIndex_CICP1[i];
+            }
+            else if ( inConfig == IVAS_AUDIO_CONFIG_STEREO )
+            {
+                /* flag to select ±90 loudspeakers instead of ±30 */
+                tmp = ( bin_upmix_stereolr_flag ) ? channelIndex_LR[i] : channelIndex_CICP2[i];
+            }
+            else if ( inConfig == IVAS_AUDIO_CONFIG_5_1 )
+#else
             if ( inConfig == IVAS_AUDIO_CONFIG_5_1 )
+#endif
             {
                 tmp = channelIndex_CICP6[i];
             }
@@ -1172,7 +1219,17 @@ ivas_error ivas_rend_openCrend(
 
     if ( ( *pCrend )->hHrtfCrend == NULL )
     {
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( ( error = ivas_rend_initCrend( *pCrend,
+                                            inConfig,
+                                            outConfig,
+                                            hHrtfCrend,
+                                            ext_rend_flag,
+                                            ( hRendCfg != NULL ) ? hRendCfg->mono_stereo_upmix_config.stereoLR : 0,
+                                            output_Fs ) ) != IVAS_ERR_OK )
+#else
         if ( ( error = ivas_rend_initCrend( *pCrend, inConfig, outConfig, hHrtfCrend, ext_rend_flag, output_Fs ) ) != IVAS_ERR_OK )
+#endif
         {
             return error;
         }
diff --git a/lib_rend/ivas_objectRenderer.c b/lib_rend/ivas_objectRenderer.c
index a4e15c79dea1ae54e130d550b50e21d8c296049a..3473eb42afc8ae8678097c9752d4fcde1e37d36d 100644
--- a/lib_rend/ivas_objectRenderer.c
+++ b/lib_rend/ivas_objectRenderer.c
@@ -60,13 +60,16 @@ static void angles_to_vec( const float radius, const float azimuth, const float
  *---------------------------------------------------------------------*/
 
 ivas_error ivas_td_binaural_open_unwrap(
-    TDREND_HRFILT_FiltSet_t **hHrtfTD,                  /* i/o: HR filter model (from file or NULL) */
-    const int32_t output_Fs,                            /* i  : Output sampling rate                */
-    const int16_t nchan_transport,                      /* i  : Number of channels                  */
-    const IVAS_FORMAT ivas_format,                      /* i  : IVAS format (ISM/MC)                */
-    const AUDIO_CONFIG transport_config,                /* i  : Transport configuration             */
-    const float *directivity,                           /* i  : Directivity pattern (used for ISM)  */
-    const float *distAtt,                               /* i  : Distance attenuation (used for ISM) */
+    TDREND_HRFILT_FiltSet_t **hHrtfTD,   /* i/o: HR filter model (from file or NULL) */
+    const int32_t output_Fs,             /* i  : Output sampling rate                */
+    const int16_t nchan_transport,       /* i  : Number of channels                  */
+    const IVAS_FORMAT ivas_format,       /* i  : IVAS format (ISM/MC)                */
+    const AUDIO_CONFIG transport_config, /* i  : Transport configuration             */
+    const float *directivity,            /* i  : Directivity pattern (used for ISM)  */
+    const float *distAtt,                /* i  : Distance attenuation (used for ISM) */
+#ifdef FIX_1419_MONO_STEREO_UMX
+    const float *radius_ms_umx, /* i  : Radius (used for mono/stereo upmix) */
+#endif
     const IVAS_OUTPUT_SETUP hTransSetup,                /* i  : Loudspeaker layout                  */
     BINAURAL_TD_OBJECT_RENDERER_HANDLE *hBinRendererTd, /* o  : TD renderer handle                  */
     int32_t *binaural_latency_ns                        /* i  : Binauralization delay               */
@@ -77,6 +80,9 @@ ivas_error ivas_td_binaural_open_unwrap(
     int16_t nS;
     int16_t SrcInd[MAX_NUM_TDREND_CHANNELS];
     const float *ls_azimuth, *ls_elevation;
+#ifdef FIX_1419_MONO_STEREO_UMX
+    float radius;
+#endif
     float Pos[3];
     float Dir[3];
     TDREND_DirAtten_t *DirAtten_p;
@@ -138,10 +144,22 @@ ivas_error ivas_td_binaural_open_unwrap(
         }
     }
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+    if ( ivas_format == MONO_FORMAT || ivas_format == STEREO_FORMAT || ivas_format == MC_FORMAT )
+#else
     if ( ivas_format == MC_FORMAT )
+#endif
     {
         switch ( transport_config )
         {
+#ifdef FIX_1419_MONO_STEREO_UMX
+            case IVAS_AUDIO_CONFIG_MONO:
+            case IVAS_AUDIO_CONFIG_STEREO:
+                /* appropriate values are set in ivas_init_decoder() */
+                ls_azimuth = hTransSetup.ls_azimuth;
+                ls_elevation = hTransSetup.ls_elevation;
+                break;
+#endif
             case IVAS_AUDIO_CONFIG_5_1:
                 ls_azimuth = ls_azimuth_CICP6;
                 ls_elevation = ls_elevation_CICP6;
@@ -175,8 +193,21 @@ ivas_error ivas_td_binaural_open_unwrap(
 
         for ( nS = 0; nS < nchan_rend; nS++ )
         {
+#ifdef FIX_1419_MONO_STEREO_UMX
+            /* set radius from render configuration file for mono/stereo upmix; otherwise 1.f */
+            radius = 1.f;
+            if ( ( transport_config == IVAS_AUDIO_CONFIG_MONO || transport_config == IVAS_AUDIO_CONFIG_STEREO ) &&
+                 radius_ms_umx != NULL )
+            {
+                radius = *radius_ms_umx;
+            }
+
+            /* Set source positions according to loudspeaker layout */
+            angles_to_vec( radius, ls_azimuth[nS], ls_elevation[nS], Pos );
+#else
             /* Set source positions according to loudspeaker layout */
             angles_to_vec( 1.0f, ls_azimuth[nS], ls_elevation[nS], Pos );
+#endif
             Dir[0] = 1.0f;
             Dir[1] = 0.0f;
             Dir[2] = 0.0f;
@@ -710,7 +741,21 @@ ivas_error ivas_td_binaural_open_ext(
         distAtt = hRendCfg->distAtt;
     }
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+    return ivas_td_binaural_open_unwrap( pTDRend->hHrtfTD,
+                                         outFs,
+                                         nchan_transport,
+                                         ivas_format,
+                                         transport_config,
+                                         directivity,
+                                         distAtt,
+                                         ( hRendCfg != NULL ) ? &hRendCfg->mono_stereo_upmix_config.radius : NULL,
+                                         hTransSetup,
+                                         &pTDRend->hBinRendererTd,
+                                         &pTDRend->binaural_latency_ns );
+#else
     return ivas_td_binaural_open_unwrap( pTDRend->hHrtfTD, outFs, nchan_transport, ivas_format, transport_config, directivity, distAtt, hTransSetup, &pTDRend->hBinRendererTd, &pTDRend->binaural_latency_ns );
+#endif
 }
 
 
diff --git a/lib_rend/ivas_output_init.c b/lib_rend/ivas_output_init.c
index 01e1d77231ff06fc84f35a4ca20448a53e8b2729..33843aaba6482dffafaa38713bbe5c5cfb3a3c77 100644
--- a/lib_rend/ivas_output_init.c
+++ b/lib_rend/ivas_output_init.c
@@ -36,7 +36,13 @@
 #include "prot.h"
 #include "ivas_prot_rend.h"
 #include "ivas_rom_com.h"
+#ifdef FIX_1419_MONO_STEREO_UMX
+#include "ivas_rom_rend.h"
+#endif
 #include "ivas_prot.h"
+#ifdef FIX_1419_MONO_STEREO_UMX
+#include <math.h>
+#endif
 #include <string.h>
 #ifdef DEBUGGING
 #include "debug.h"
@@ -166,9 +172,17 @@ void ivas_output_init(
         {
             case IVAS_AUDIO_CONFIG_MONO:
                 hOutSetup->is_loudspeaker_setup = 1;
+#ifdef FIX_1419_MONO_STEREO_UMX
+                hOutSetup->is_planar_setup = 1;
+                hOutSetup->ls_azimuth = ls_azimuth_CICP1;
+                hOutSetup->ls_elevation = ls_elevation_CICP1;
+#endif
                 break;
             case IVAS_AUDIO_CONFIG_STEREO:
                 hOutSetup->is_loudspeaker_setup = 1;
+#ifdef FIX_1419_MONO_STEREO_UMX
+                hOutSetup->is_planar_setup = 1;
+#endif
                 hOutSetup->ls_azimuth = ls_azimuth_CICP2;
                 hOutSetup->ls_elevation = ls_elevation_CICP2;
                 break;
@@ -276,10 +290,24 @@ int16_t ivas_get_nchan_buffers_dec(
     if ( st_ivas->ivas_format == MONO_FORMAT )
     {
         nchan_out_buff = st_ivas->hDecoderConfig->nchan_out;
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( output_config == IVAS_AUDIO_CONFIG_BINAURAL_ROOM_IR &&
+             ( st_ivas->hDecoderConfig->Opt_Headrotation || st_ivas->hDecoderConfig->Opt_ExternalOrientation ) )
+        {
+            nchan_out_buff = max( nchan_out_buff, st_ivas->hIntSetup.nchan_out_woLFE + st_ivas->hIntSetup.num_lfe );
+        }
+#endif
     }
     else if ( st_ivas->ivas_format == STEREO_FORMAT )
     {
         nchan_out_buff = max( st_ivas->hDecoderConfig->nchan_out, CPE_CHANNELS );
+#ifdef FIX_1419_MONO_STEREO_UMX
+        if ( output_config == IVAS_AUDIO_CONFIG_BINAURAL_ROOM_IR &&
+             ( st_ivas->hDecoderConfig->Opt_Headrotation || st_ivas->hDecoderConfig->Opt_ExternalOrientation ) )
+        {
+            nchan_out_buff = max( nchan_out_buff, st_ivas->hIntSetup.nchan_out_woLFE + st_ivas->hIntSetup.num_lfe );
+        }
+#endif
     }
     else if ( st_ivas->ivas_format == ISM_FORMAT )
     {
@@ -435,6 +463,115 @@ ivas_error ivas_output_buff_dec(
     return IVAS_ERR_OK;
 }
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+/*---------------------------------------------------------------------*
+ * ms_upmix_validate_config()
+ *
+ *
+ *---------------------------------------------------------------------*/
+
+ivas_error ms_upmix_validate_config(
+    IVAS_MS_UMX_CONF_HANDLE pMsUpmixConfig, /* i/o: Mono/Stereo upmix configuration    */
+    const IVAS_FORMAT ivasFormat,           /* i  : IVAS Decoder input configuration   */
+    const IVAS_AUDIO_CONFIG outConfig       /* i  : IVAS Decoder output configuration  */
+)
+{
+    int16_t i;
+    float azi_abs[2];
+    float ele_abs[2];
+
+    if ( pMsUpmixConfig == NULL )
+    {
+        return IVAS_ERR_UNEXPECTED_NULL_POINTER;
+    }
+
+    /* skip validation if non spatial; values aren't used */
+    if ( !pMsUpmixConfig->spatialEnabled )
+    {
+        return IVAS_ERR_OK;
+    }
+
+    /* validate radius */
+    if ( pMsUpmixConfig->radius < 0.f || pMsUpmixConfig->radius > 15.75f )
+    {
+        return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "Radius must be between 0 and 15.75" );
+    }
+
+    /* zero radius corresponds to non-spatial */
+    if ( pMsUpmixConfig->radius == 0.f )
+    {
+        pMsUpmixConfig->spatialEnabled = FALSE;
+        return IVAS_ERR_OK;
+    }
+
+    /* obtain absolute values */
+    for ( i = 0; i < 2; i++ )
+    {
+        azi_abs[i] = fabsf( pMsUpmixConfig->azi[i] );
+        ele_abs[i] = fabsf( pMsUpmixConfig->ele[i] );
+    }
+
+    /* validate speaker positions */
+    if ( ivasFormat == MONO_FORMAT )
+    {
+        if ( azi_abs[0] != 0 )
+        {
+            return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "Mono cannot be panned" );
+        }
+        if ( ele_abs[0] != 0 )
+        {
+            return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "Mono cannot be panned" );
+        }
+    }
+    else if ( ivasFormat == STEREO_FORMAT )
+    {
+        if ( outConfig == IVAS_AUDIO_CONFIG_BINAURAL_ROOM_IR )
+        {
+            /* validate provided positions match BRIR */
+            if ( ( azi_abs[0] != 30 && azi_abs[0] != 90 ) ||
+                 ( azi_abs[1] != 30 && azi_abs[1] != 90 ) )
+            {
+                return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "BINAURAL_ROOM_IR only supports ±30 and ±90 degree azimuth" );
+            }
+            if ( ele_abs[0] != 0 || ele_abs[1] != 0 )
+            {
+                return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "BINAURAL_ROOM_IR does not allow nonzero elevation" );
+            }
+
+            /* flag to select ±90 azi loudspeakers */
+            if ( azi_abs[0] == 90 && azi_abs[1] == 90 )
+            {
+                pMsUpmixConfig->stereoLR = TRUE;
+            }
+        }
+        else /* HRIR based formats and split rendering */
+        {
+            /* enforce symmetry */
+            if ( pMsUpmixConfig->azi[0] != -pMsUpmixConfig->azi[1] )
+            {
+                return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "Panning stereo pair with asymmetric azimuth is not allowed" );
+            }
+            if ( pMsUpmixConfig->ele[0] != pMsUpmixConfig->ele[1] )
+            {
+                return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "Panning stereo pair with differring elevation is not allowed" );
+            }
+
+            /* restrict values */
+            if ( ( azi_abs[0] > 90 ) || ( azi_abs[1] > 90 ) )
+            {
+                return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "Panning stereo pair beyond |90| degrees azimuth is not allowed" );
+            }
+            if ( ( ele_abs[0] > 45 ) || ( ele_abs[1] > 45 ) )
+            {
+                return IVAS_ERROR( IVAS_ERR_INVALID_RENDER_CONFIG, "Panning stereo pair beyond |45| degrees of elevation is not allowed" );
+            }
+        }
+    }
+
+    return IVAS_ERR_OK;
+}
+#endif
 
 /*---------------------------------------------------------------------*
  * is_split_rendering_enabled()
diff --git a/lib_rend/ivas_prot_rend.h b/lib_rend/ivas_prot_rend.h
index ae80304ee04ae85ea7bf3e40026aa3718a8004a0..224b393c48faf97d7c963909baa093769665f5b0 100644
--- a/lib_rend/ivas_prot_rend.h
+++ b/lib_rend/ivas_prot_rend.h
@@ -651,6 +651,9 @@ ivas_error ivas_td_binaural_open_unwrap(
     const AUDIO_CONFIG transport_config,                        /* i  : Transport configuration                 */
     const float *directivity,                                   /* i  : Directivity pattern (used for ISM)      */
     const float *distAtt,                                       /* i  : Distance attenuation (used for ISM)     */
+#ifdef FIX_1419_MONO_STEREO_UMX
+    const float *radius_ms_umx,                                 /* i  : Radius (used for mono/stereo upmix)     */
+#endif
     const IVAS_OUTPUT_SETUP hTransSetup,                        /* i  : Loudspeaker layout                      */
     BINAURAL_TD_OBJECT_RENDERER_HANDLE *hBinRendererTd,         /* o  : TD renderer handle                      */
     int32_t *binaural_latency_ns                                /* i  : Binauralization delay                   */
@@ -1343,6 +1346,13 @@ ivas_error ivas_render_config_init_from_rom(
     RENDER_CONFIG_HANDLE *hRenderConfig                         /* i/o: Renderer config handle                  */
 );
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+ivas_error ms_upmix_validate_config(
+    IVAS_MS_UMX_CONF_HANDLE pMsUpmixConfig, /* i/o: Mono/Stereo upmix configuration    */
+    const IVAS_FORMAT ivasFormat,           /* i  : IVAS Decoder input configuration   */
+    const IVAS_AUDIO_CONFIG outConfig       /* i  : IVAS Decoder output configuration  */
+);
+#endif
 
 /*----------------------------------------------------------------------------------*
  * Quaternion operations
diff --git a/lib_rend/ivas_render_config.c b/lib_rend/ivas_render_config.c
index c3a39b426e39a0c1f372a5e0f88464c1c7e4c18b..e1290b54a760340dfe93674e817af8aff3d4e4a1 100644
--- a/lib_rend/ivas_render_config.c
+++ b/lib_rend/ivas_render_config.c
@@ -135,6 +135,15 @@ ivas_error ivas_render_config_init_from_rom(
     ( *hRenderConfig )->distAtt[0] = 15.75f; /* Default max dist */
     ( *hRenderConfig )->distAtt[1] = 1.0f;   /* Default ref dist */
     ( *hRenderConfig )->distAtt[2] = 1.0f;   /* Default rolloff factor */
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+    /* Mono/Stereo upmix configuration */
+    ( *hRenderConfig )->mono_stereo_upmix_config.spatialEnabled = FALSE;
+    ( *hRenderConfig )->mono_stereo_upmix_config.stereoLR = FALSE;
+    ( *hRenderConfig )->mono_stereo_upmix_config.radius = 0.f;
+    set_zero( &( *hRenderConfig )->mono_stereo_upmix_config.azi[0], 2 );
+    set_zero( &( *hRenderConfig )->mono_stereo_upmix_config.ele[0], 2 );
+#endif
 
     /* ISAR-related parameters */
     ( *hRenderConfig )->split_rend_config.splitRendBitRate = ISAR_MAX_SPLIT_REND_BITRATE;
diff --git a/lib_rend/ivas_rom_rend.c b/lib_rend/ivas_rom_rend.c
index 3f4b906bd6fdaa8159f22abe9ed3fb2686c3fd6e..924f685adb0d07302bef9dd176f246e5ff6e278e 100644
--- a/lib_rend/ivas_rom_rend.c
+++ b/lib_rend/ivas_rom_rend.c
@@ -205,6 +205,11 @@ const int16_t sba_map_tc_512[11] =
 * 13 = 135, 35
 * 14 = -135, 35
 */
+#ifdef FIX_1419_MONO_STEREO_UMX
+const int16_t channelIndex_CICP1[1] = { 2 };
+const int16_t channelIndex_CICP2[2] = { 0, 1 };
+const int16_t channelIndex_LR[2] = { 7, 8 };
+#endif
 const int16_t channelIndex_CICP6[5] = { 0, 1, 2, 5, 6 };
 const int16_t channelIndex_CICP12[7] = { 0, 1, 2, 5, 6, 3, 4 };
 const int16_t channelIndex_CICP14[7] = { 0, 1, 2, 5, 6, 9, 10 };
@@ -388,8 +393,8 @@ const float ivas_reverb_default_DSR[IVAS_REVERB_DEFAULT_N_BANDS] =
  *----------------------------------------------------------------------------------*/
 
 /* CICP1 - Mono */
-const float ls_azimuth_CICP1[1] = { 0.0f };
-const float ls_elevation_CICP1[1] = { 0.0f };
+const float ls_azimuth_CICP1[1] =       { 0.0f };
+const float ls_elevation_CICP1[1] =     { 0.0f };
 
 
 /*----------------------------------------------------------------------------------*
@@ -619,6 +624,15 @@ const LS_CONVERSION_MATRIX ls_conversion_cicp19_cicp16[] =
 };
 
 /* Upmix matrices */
+#ifdef FIX_1419_MONO_STEREO_UMX
+const LS_CONVERSION_MATRIX ls_conversion_mono_cicpX[] = {
+    /* First row indicates the number of non-zero elements and the number of matrix columns */
+    {1,  12.0f},
+    /* Index of non-zero element, value of non-zero element*/
+    {2,  1.0f},
+};
+
+#endif
 const LS_CONVERSION_MATRIX ls_conversion_cicp12_cicp14[] =
 {
     /* First row indicates the number of non-zero elements and the number of matrix columns */
@@ -704,6 +718,9 @@ const LS_CONVERSION_MATRIX ls_conversion_cicp16_cicp19[] =
 const LS_CONVERSION_MAPPING ls_conversion_mapping[LS_SETUP_CONVERSION_NUM_MAPPINGS] =
 {
     /* Dowmix mappings - NULL is a special case for MONO / STEREO downmix */
+#ifdef FIX_1419_MONO_STEREO_UMX
+    {IVAS_AUDIO_CONFIG_STEREO, IVAS_AUDIO_CONFIG_MONO, NULL},
+#endif
     {IVAS_AUDIO_CONFIG_5_1,   IVAS_AUDIO_CONFIG_MONO, NULL},
     {IVAS_AUDIO_CONFIG_7_1,   IVAS_AUDIO_CONFIG_MONO, NULL},
     {IVAS_AUDIO_CONFIG_5_1_2, IVAS_AUDIO_CONFIG_MONO, NULL},
@@ -731,6 +748,14 @@ const LS_CONVERSION_MAPPING ls_conversion_mapping[LS_SETUP_CONVERSION_NUM_MAPPIN
     {IVAS_AUDIO_CONFIG_7_1_4, IVAS_AUDIO_CONFIG_5_1_4, ls_conversion_cicp19_cicp16},
 
     /* Upmix mappings - NULL implies a 1:1 upmix */
+#ifdef FIX_1419_MONO_STEREO_UMX
+    {IVAS_AUDIO_CONFIG_MONO, IVAS_AUDIO_CONFIG_5_1,   ls_conversion_mono_cicpX},
+    {IVAS_AUDIO_CONFIG_MONO, IVAS_AUDIO_CONFIG_7_1,   ls_conversion_mono_cicpX},
+    {IVAS_AUDIO_CONFIG_MONO, IVAS_AUDIO_CONFIG_5_1_2, ls_conversion_mono_cicpX},
+    {IVAS_AUDIO_CONFIG_MONO, IVAS_AUDIO_CONFIG_5_1_4, ls_conversion_mono_cicpX},
+    {IVAS_AUDIO_CONFIG_MONO, IVAS_AUDIO_CONFIG_7_1_4, ls_conversion_mono_cicpX},
+
+#endif
     {IVAS_AUDIO_CONFIG_STEREO, IVAS_AUDIO_CONFIG_5_1,   NULL},
     {IVAS_AUDIO_CONFIG_STEREO, IVAS_AUDIO_CONFIG_7_1,   NULL},
     {IVAS_AUDIO_CONFIG_STEREO, IVAS_AUDIO_CONFIG_5_1_2, NULL},
diff --git a/lib_rend/ivas_rom_rend.h b/lib_rend/ivas_rom_rend.h
index 927287ecd96a2b33cb061c32d40013623da77469..2373f80ed09b72df057148019e89e60842f195b7 100644
--- a/lib_rend/ivas_rom_rend.h
+++ b/lib_rend/ivas_rom_rend.h
@@ -67,6 +67,11 @@ extern const int16_t sba_map_tc_512[11];
  * FASTCONV and PARAMETRIC binaural renderer ROM tables
  *----------------------------------------------------------------------------------*/
 
+#ifdef FIX_1419_MONO_STEREO_UMX
+extern const int16_t channelIndex_CICP1[1];
+extern const int16_t channelIndex_CICP2[2];
+extern const int16_t channelIndex_LR[2];
+#endif
 extern const int16_t channelIndex_CICP6[5];
 extern const int16_t channelIndex_CICP12[7];
 extern const int16_t channelIndex_CICP14[7];
diff --git a/lib_rend/ivas_rotation.c b/lib_rend/ivas_rotation.c
index b9286d3d96b01ae9bddcb24319badb17319c024c..c4c30ac160673028cc6918489fec3c975e05d419 100644
--- a/lib_rend/ivas_rotation.c
+++ b/lib_rend/ivas_rotation.c
@@ -361,7 +361,11 @@ void rotateFrame_sd(
 )
 {
     int16_t i, j;
+#ifdef FIX_1419_MONO_STEREO_UMX
+    int16_t nchan, num_lfe, index_lfe;
+#else
     int16_t nchan, index_lfe;
+#endif
     int16_t ch_in, ch_in_woLFE, ch_out, ch_out_woLFE;
     int16_t azimuth, elevation;
 
@@ -374,6 +378,9 @@ void rotateFrame_sd(
     push_wmops( "rotateFrame_sd" );
 
     nchan = hTransSetup.nchan_out_woLFE + hTransSetup.num_lfe;
+#ifdef FIX_1419_MONO_STEREO_UMX
+    num_lfe = hTransSetup.num_lfe;
+#endif
     index_lfe = hTransSetup.index_lfe[0];
 
     tmp = 1.0f / ( subframe_len - 1 );
@@ -400,7 +407,11 @@ void rotateFrame_sd(
         }
 
         /* input channel index without LFE */
+#ifdef FIX_1419_MONO_STEREO_UMX
+        ch_in_woLFE = ( ( num_lfe > 0 ) && ( ch_in >= index_lfe ) ) ? ch_in - 1 : ch_in;
+#else
         ch_in_woLFE = ( ch_in >= index_lfe ) ? ch_in - 1 : ch_in;
+#endif
 
         /* gains for previous subframe rotation */
         rotateAziEle( hTransSetup.ls_azimuth[ch_in_woLFE], hTransSetup.ls_elevation[ch_in_woLFE], &azimuth, &elevation, hCombinedOrientationData->Rmat_prev[0], hTransSetup.is_planar_setup );
@@ -417,7 +428,12 @@ void rotateFrame_sd(
                 }
 
                 /* output channel index without LFE */
+#ifdef FIX_1419_MONO_STEREO_UMX
+                ch_out_woLFE = ( ( num_lfe > 0 ) && ( ch_out >= index_lfe ) ) ? ch_out - 1 : ch_out;
+#else
                 ch_out_woLFE = ( ch_out >= index_lfe ) ? ch_out - 1 : ch_out;
+#endif
+
 
                 gains_prev[ch_in][ch_out] = tmp_gains[ch_out_woLFE];
             }
@@ -439,7 +455,11 @@ void rotateFrame_sd(
                 }
 
                 /* output channel index without LFE */
+#ifdef FIX_1419_MONO_STEREO_UMX
+                ch_out_woLFE = ( ( num_lfe > 0 ) && ( ch_out >= index_lfe ) ) ? ch_out - 1 : ch_out;
+#else
                 ch_out_woLFE = ( ch_out >= index_lfe ) ? ch_out - 1 : ch_out;
+#endif
 
                 gains[ch_in][ch_out] = tmp_gains[ch_out_woLFE];
             }
diff --git a/lib_rend/lib_rend.c b/lib_rend/lib_rend.c
index 4bb1024aae19eae7aa5e70822b9296b8052eef83..87cd2771842841b700e99a6512e77b059bfe3c07 100644
--- a/lib_rend/lib_rend.c
+++ b/lib_rend/lib_rend.c
@@ -6229,7 +6229,8 @@ static ivas_error renderMcToBinaural(
         }
     }
 
-    if ( ( inConfig == IVAS_AUDIO_CONFIG_LS_CUSTOM ) || ( combinedOrientationEnabled && ( inConfig == IVAS_AUDIO_CONFIG_5_1 || inConfig == IVAS_AUDIO_CONFIG_7_1 ) ) )
+    if ( ( inConfig == IVAS_AUDIO_CONFIG_LS_CUSTOM ) ||
+         ( combinedOrientationEnabled && ( inConfig == IVAS_AUDIO_CONFIG_5_1 || inConfig == IVAS_AUDIO_CONFIG_7_1 ) ) )
     {
         copyBufferTo2dArray( mcInput->base.inputBuffer, tmpRendBuffer );
 
diff --git a/lib_util/render_config_reader.c b/lib_util/render_config_reader.c
index 7729efbc7cb0ffe9ca4174f7aa12ea7012c5a67c..01bff48ac33b3eb99ff728b46f6ab8f09152283e 100644
--- a/lib_util/render_config_reader.c
+++ b/lib_util/render_config_reader.c
@@ -2591,6 +2591,46 @@ ivas_error RenderConfigReader_read(
                 free( pValue );
                 acIdx++;
             }
+#ifdef FIX_1419_MONO_STEREO_UMX
+            else if ( strcmp( chapter, "MSUPMIX" ) == 0 && strlen( pParams ) != 0 )
+            {
+                params_idx = 0;
+                pValue = (char *) calloc( strlen( pParams ), sizeof( char ) );
+                while ( sscanf( pParams + params_idx, "%64[^=]=%[^;];", item, pValue ) == 2 )
+                {
+                    params_idx += (int32_t) ( strlen( item ) + strlen( pValue ) + 2 );
+                    if ( strcmp( item, "AZIMUTH" ) == 0 )
+                    {
+                        if ( read_txt_vector( pValue, 2, &hRenderConfig->mono_stereo_upmix_config.azi[0] ) )
+                        {
+                            errorHandler( item, ERROR_VALUE_INVALID );
+                            return IVAS_ERR_INVALID_RENDER_CONFIG;
+                        }
+                        /* set flag to signal that spatial rendering is enabled */
+                        hRenderConfig->mono_stereo_upmix_config.spatialEnabled = 1;
+                    }
+                    else if ( strcmp( item, "ELEVATION" ) == 0 )
+                    {
+                        if ( read_txt_vector( pValue, 2, &hRenderConfig->mono_stereo_upmix_config.ele[0] ) )
+                        {
+                            errorHandler( item, ERROR_VALUE_INVALID );
+                            return IVAS_ERR_INVALID_RENDER_CONFIG;
+                        }
+                        /* set flag to signal that spatial rendering is enabled */
+                        hRenderConfig->mono_stereo_upmix_config.spatialEnabled = 1;
+                    }
+                    else if ( strcmp( item, "RADIUS" ) == 0 )
+                    {
+                        if ( !sscanf( pValue, "%f", &hRenderConfig->mono_stereo_upmix_config.radius ) )
+                        {
+                            errorHandler( item, ERROR_VALUE_INVALID );
+                        }
+                        /* set flag to signal that spatial rendering is enabled */
+                        hRenderConfig->mono_stereo_upmix_config.spatialEnabled = 1;
+                    }
+                }
+            }
+#endif
             else if ( strcmp( chapter, "SPLITREND" ) == 0 && strlen( pParams ) != 0 )
             {
                 params_idx = 0;
@@ -2976,6 +3016,14 @@ ivas_error RenderConfigReader_getAcousticEnvironment(
     {
         return IVAS_ERR_UNEXPECTED_NULL_POINTER;
     }
+#ifdef FIX_1419_MONO_STEREO_UMX
+
+    /* case when config file contains no acoustic environment, the defaults are already set from ROM */
+    if ( id == 65535 && pRenderConfigReader->nAE == 0 )
+    {
+        return IVAS_ERR_OK;
+    }
+#endif
 
     /* case when -aeid is not specified, select first ID from config file */
     if ( id == 65535 && pRenderConfigReader->nAE > 0 )