diff --git a/lib_util/ivas_rtp_pi_data.c b/lib_util/ivas_rtp_pi_data.c
index 710121db6822e0042df38728e01d878d62601fbd..b9b7bcc7e44fbd19ca75570c793acd9e697bc588 100644
--- a/lib_util/ivas_rtp_pi_data.c
+++ b/lib_util/ivas_rtp_pi_data.c
@@ -1037,13 +1037,13 @@ static ivas_error packISMGain( const IVAS_PIDATA_GENERIC *piData, uint8_t *buffe
     for ( n = 0; n < ism_gain->numObjects; n++ )
     {
         gain = (int16_t) ism_gain->dB[n];
-        idx = min( -gain, 97 );
+        idx = min( -gain, 25 );
         if ( gain > 0 )
         {
-            idx += 97;
+            idx += 25;
         }
 
-        buffer[nBytes++] = ( idx & MASK_7BIT ) << 1;
+        buffer[nBytes++] = ( idx & MASK_6BIT ) << 2;
     }
     *nBytesWritten = nBytes;
     return IVAS_ERR_OK;
@@ -1067,21 +1067,21 @@ static ivas_error unpackISMGain( const uint8_t *buffer, uint32_t numDataBytes, I
     /* Unpack ID for each object (1 byte each) */
     for ( n = 0; n < ism_gain->numObjects; n++ )
     {
-        idx = ( buffer[n] ) >> 1;
+        idx = ( buffer[n] ) >> 2;
         /* negative gains*/
-        if ( idx < 97 )
+        if ( idx < 25 )
         {
             ism_gain->dB[n] = -(int8_t) ( idx );
         }
         /* Set to min for muting, to be interpreted as -Inf */
-        else if ( idx == 97 )
+        else if ( idx == 25 )
         {
             ism_gain->dB[n] = -128;
         }
         /* postive gains */
-        else if ( idx < 101 )
+        else if ( idx < 38 )
         {
-            ism_gain->dB[n] = (int8_t) idx - 97;
+            ism_gain->dB[n] = (int8_t) idx - 25;
         }
         else
         {
@@ -1249,7 +1249,7 @@ static ivas_error unpackISMDirectivity( const uint8_t *buffer, uint32_t numDataB
 
         if ( idx == 0 )
         {
-            ism_directivity->directivity[n].outerAttenuationdB = -32768.0f; /* corresponds to muting */
+            ism_directivity->directivity[n].outerAttenuationdB = -128.0f; /* corresponds to muting */
         }
         else
         {
@@ -1339,13 +1339,13 @@ static ivas_error packReverseISMGain( const IVAS_PIDATA_GENERIC *piData, uint8_t
 
     buffer[nBytes++] = ( r_ism_gain->piDataType & MASK_5BIT ); /* PF/PM populated during final packing */
     gain = (int16_t) r_ism_gain->dB;
-    idx = min( -gain, 97 );
+    idx = min( -gain, 25 );
     if ( gain > 0 )
     {
-        idx += 97;
+        idx += 25;
     }
 
-    buffer[nBytes++] = ( idx & MASK_7BIT ) << 1;
+    buffer[nBytes++] = ( idx & MASK_6BIT ) << 2;
     *nBytesWritten = nBytes;
     return IVAS_ERR_OK;
 }
@@ -1365,21 +1365,21 @@ static ivas_error unpackReverseISMGain( const uint8_t *buffer, uint32_t numDataB
     r_ism_gain->piDataType = IVAS_PI_R_ISM_GAIN;
 
     /* Unpack gain */
-    idx = ( *buffer ) >> 1;
+    idx = ( *buffer ) >> 2;
     /* negative gains*/
-    if ( idx < 97 )
+    if ( idx < 25 )
     {
         r_ism_gain->dB = -(int8_t) ( idx );
     }
     /* Set to min for muting, to be interpreted as -Inf */
-    else if ( idx == 97 )
+    else if ( idx == 25 )
     {
         r_ism_gain->dB = -128;
     }
     /* postive gains */
-    else if ( idx < 101 )
+    else if ( idx < 38 )
     {
-        r_ism_gain->dB = (int8_t) idx - 97;
+        r_ism_gain->dB = (int8_t) idx - 25;
     }
     else
     {
diff --git a/tests/rtp/ivasrtp.py b/tests/rtp/ivasrtp.py
index 224df7472e22197c14ec8366b63c1079d679311a..5b1bb2be7948643fbe9b8c01768e4b3193a64564 100644
--- a/tests/rtp/ivasrtp.py
+++ b/tests/rtp/ivasrtp.py
@@ -639,12 +639,12 @@ roomDimensionValue = [
     90.51,
 ]
 absorptionCoeffValues = [0.0800, 0.1656, 0.3430, 0.7101]
-ismGains = list(range(0, -97, -1)) + [-float("inf")] + list(range(1, 4))
+ismGains = list(range(0, -25, -1)) + [-128] + list(range(1, 13)) # -128 corresponds to -Inf
 refDistances = [round(x * 0.1, 1) for x in range(1, 65)]
 maxDistances = list(range(1,65))
 rolloffFactors = [round(x * 0.1, 1) for x in range(0, 41)]
 innerOuterAngles = list(range(0,361,15))
-outerAttenuations = [-float("inf")] + list(range(-90,1,3))
+outerAttenuations = [-128] + list(range(-90,1,3)) # -128 corresponds to -Inf
 codedFormats = list(FORMATS)
 codedSubFormats = list(SUBFORMATS)
 PiTypeNames = list(PIDATAS)
@@ -1052,7 +1052,7 @@ def unpackISMGain(bitstrm: ConstBitStream, piSize: int) -> ISM_GAIN:
     assert piSize == 1 or piSize == 2 or piSize == 3 or piSize == 4, "Incorrect PI Data Size for ISM_GAIN"
     IsmGain = list()
     for _ in range(piSize):
-        IsmGain.append(bitstrm.read(7).uint)
+        IsmGain.append(bitstrm.read(6).uint)
         bitstrm.bytealign()
     return ISM_GAIN(gains=IsmGain)
 
@@ -1062,8 +1062,8 @@ def packISMGain(bitstrm: BitStream, data: any):
     assert len(ism_gain.gains) <= 4, "Maximum 4 objects"
     for gain in ism_gain.gains:
         gain_idx = getListIndex(ismGains, gain)
-        bitstrm.append(f'uint:7={gain_idx}')
-        bitstrm.append(f'uint:1=0')     
+        bitstrm.append(f'uint:6={gain_idx}')
+        bitstrm.append(f'uint:2=0')     
 
 def unpackISMDistanceAttenuation(bitstrm: ConstBitStream, piSize: int) -> ISM_DISTANCE_ATTENUATION:
     ref_dist = None
@@ -1131,15 +1131,15 @@ def packReverseISMID(bitstrm: BitStream, data: any):
 
 def unpackReverseISMGain(bitstrm: ConstBitStream, piSize: int) -> R_ISM_GAIN:
     assert piSize == 1, "Incorrect PI Data Size for R_ISM_GAIN"
-    gain = bitstrm.read(7).uint
+    gain = bitstrm.read(6).uint
     return R_ISM_GAIN(gain=gain)
 
 def packReverseISMGain(bitstrm: BitStream, data: any):
     assert type(data) == R_ISM_GAIN, "Data of type R_ISM_GAIN is expected"
     r_ism_gain = cast(R_ISM_GAIN, data)
     gain_idx = getListIndex(ismGains, r_ism_gain.gain)
-    bitstrm.append(f'uint:7={gain_idx}')
-    bitstrm.append(f'uint:1=0')
+    bitstrm.append(f'uint:6={gain_idx}')
+    bitstrm.append(f'uint:2=0')
 
 def unpackReverseISMDirection(bitstrm: ConstBitStream, piSize: int) -> R_ISM_DIRECTION:
     assert piSize == 2, "Incorrect PI Data Size for R_ISM_DIRECTION"
diff --git a/tests/rtp/test_rtp.py b/tests/rtp/test_rtp.py
index b8a542a4ed07d8ee271cb4f1643d4c8d30200f8a..53cb6488c5768ab3266bcaf3fe3a763592e126db 100644
--- a/tests/rtp/test_rtp.py
+++ b/tests/rtp/test_rtp.py
@@ -272,14 +272,14 @@ def generatePiData(startTs: int, endTs: int) -> dict:
 
     someNumISM = lambda : ISM_NUM(num=random.randint(1, 4))
     someISMIds = lambda num_ism : ISM_ID(ids=[int(random.getrandbits(8)) for _ in range(num_ism)])
-    someISMGains = lambda num_ism : ISM_GAIN(gains=[int(random.randint(-96,3)) for _ in range(num_ism)])
+    someISMGains = lambda num_ism : ISM_GAIN(gains=[random.choice([int(random.randint(-24,12)), -128]) for _ in range(num_ism)]) # -128 corresponds to -Inf
     someISMOrientations = lambda num_ism : [ORIENTATION(w=2*random.random()-1.0, x=2*random.random()-1.0, y=2*random.random()-1.0, z=2*random.random()-1.0) for _ in range(num_ism)]
     someISMPositions = lambda num_ism : [POSITION( x=random.randint(-32788, 32767)/100.0, y=random.randint(-32788, 32767)/100.0, z=random.randint(-32788, 32767)/100.0) for _ in range(num_ism)]
     someISMDistanceAttenuations = lambda num_ism : [DISTANCE_ATTENUATION(ref_dist=random.randint(1,64)/10.0, max_dist=random.randint(1,64), roll_off=random.randint(0,40)/10.0) for _ in range(num_ism)]
-    someISMDirectivities = lambda num_ism : [DIRECTIVITY(inner_ang=random.randint(0,24)*15, outer_ang=random.randint(0,24)*15, outer_att=random.randint(-30,0)*3) for _ in range(num_ism)]
+    someISMDirectivities = lambda num_ism : [DIRECTIVITY(inner_ang=random.randint(0,24)*15, outer_ang=random.randint(0,24)*15, outer_att=random.choice([random.randint(-30,0)*3, -128])) for _ in range(num_ism)] # -128 corresponds to -Inf
 
     someReverseISMId = lambda : R_ISM_ID(id=(random.getrandbits(8)))
-    someReverseISMGain = lambda : R_ISM_GAIN(gain=int(random.randint(-96,3)))
+    someReverseISMGain = lambda : R_ISM_GAIN(gain=random.choice([int(random.randint(-24,12)), -128]))
     someReverseISMDirection = lambda : R_ISM_DIRECTION( azi=random.randint(1,512) * azimuthStepSize - 180.0, elev=random.randint(0,127) * elevationStepSize - 90.0 )
 
     for ts in range(startTs, endTs, 320):