Usage of extract_l() with values out of range

Basic info

  • Float reference:
    • Encoder (float):
    • Decoder (float):
  • Fixed point:
    • Encoder (fixed): 7bf796ef
    • Decoder (fixed):

Bug description

In several places extract_l() is used to convert a Word32 to a Word16, but this will most likely cause unexpected results if the values is out of range for a Word16 and there is no check of any sort.

One example: for the encoder the following test case triggers a out of range condition in estDownmixGain_fx()

IVAS_cod -masa 2 ../ltv/ltv48_MASA2TC.met -dtx -max_band swb 13200 32 ../ltv/ltv48_MASA2TC_32khz.wav out.192

For any usage of extract_l() where its not about separating bit fields but converting numbers, it is recommended to add a check like this:

assert( value32 <= MAX_16 && value32 >= MIN_16 ); value16 = extract_l( value32 );

diff --git a/lib_enc/ivas_stereo_ica_enc_fx.c b/lib_enc/ivas_stereo_ica_enc_fx.c
index 234652072..c3f420f93 100644
--- a/lib_enc/ivas_stereo_ica_enc_fx.c
+++ b/lib_enc/ivas_stereo_ica_enc_fx.c
@@ -1304,9 +1304,18 @@ static void estDownmixGain_fx(
     currentGain_log10 = BASOP_Util_Log10( L_deposit_h( currentGain ), currentGain_e ); // Output in Q25
     // multiplication result will be Q25 should be fit to Q15 hence right shift by 10.
     // Q25 - Q10 = Q15
+#if 1
+    Word32 checkv;
+    checkv = L_shr( Madd_32_16( Mpy_32_16_1( prevTargetGain_log10, alpha ), currentGain_log10, sub( MAX_16, alpha ) ), Q10 );
+    assert( checkv <= MAX_16 && checkv >= MIN_16 );
+    currentGain = extract_l( checkv ); /* Q15 */
+    currentGain_e = 0;
+    move16();
+#else
     currentGain = extract_l( L_shr( Madd_32_16( Mpy_32_16_1( prevTargetGain_log10, alpha ), currentGain_log10, sub( MAX_16, alpha ) ), Q10 ) ); /* Q15 */
     currentGain_e = 0;
     move16();
+#endif
 
     test();
     IF( EQ_16( element_mode, IVAS_CPE_TD ) && hStereoClassif != NULL )

Ways to reproduce

  1. Add assert as described above.
  2. Run
IVAS_cod -masa 2 ../ltv/ltv48_MASA2TC.met -dtx -max_band swb 13200 32 ../ltv/ltv48_MASA2TC_32khz.wav out.192