shithub: opus

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ref: 1e0805d74f440adbf5829c8a8179fc30a24c5746
parent: 8a7543c49e6cb944258b4cbe5598091e93b290ad
author: Jean-Marc Valin <[email protected]>
date: Mon Oct 3 09:52:18 EDT 2011 

Delaying SILK stereo->mono transitions by two frames

Gets rid of some more glitches caused by the decoder resampler


--- a/silk/enc_API.c
+++ b/silk/enc_API.c
@@ -137,11 +137,14 @@
    }
 
    i=0;
-   if ( id==0 ) {
-      for ( ; i < len>>1; i++ ) {
-         out[ i ] = silk_RSHIFT_ROUND( silk_SMLABB( silk_SMULBB( x1[ 2*i ], g1 ), x2[ 2*i ], g2 ), 14 );
-         g1 += delta;
-         g2 -= delta;
+   if (to_mono != 2)
+   {
+      if ( id==0 ) {
+         for ( ; i < len>>1; i++ ) {
+            out[ i ] = silk_RSHIFT_ROUND( silk_SMLABB( silk_SMULBB( x1[ 2*i ], g1 ), x2[ 2*i ], g2 ), 14 );
+            g1 += delta;
+            g2 -= delta;
+         }
       }
    }
    if (to_mono) {
@@ -153,7 +156,6 @@
          out[ i ] = x1[ 2*i ];
       }
    }
-   /*fprintf(stderr, "%d %d %d\n", g1, g2, to_mono);*/
 }
 
 /**************************/
@@ -256,8 +258,8 @@
         /* Resample and write to buffer */
         if( encControl->nChannelsAPI == 2 && encControl->nChannelsInternal == 2 ) {
             int id = psEnc->state_Fxx[ 0 ].sCmn.nFramesEncoded;
-            if ( encControl->toMono ) {
-                stereo_crossmix( samplesIn, buf, 0, nSamplesFromInput, 1, id );
+            if ( encControl->toMono > 0) {
+                stereo_crossmix( samplesIn, buf, 0, nSamplesFromInput, encControl->toMono, id );
             } else if( psEnc->nPrevChannelsInternal == 1 || encControl->toMono == -1 ) {
                 stereo_crossmix( samplesIn, buf, 0, nSamplesFromInput, 0, id );
             } else {
@@ -275,9 +277,9 @@
 
             nSamplesToBuffer  = psEnc->state_Fxx[ 1 ].sCmn.frame_length - psEnc->state_Fxx[ 1 ].sCmn.inputBufIx;
             nSamplesToBuffer  = silk_min( nSamplesToBuffer, 10 * nBlocksOf10ms * psEnc->state_Fxx[ 1 ].sCmn.fs_kHz );
-            if ( encControl->toMono ) {
-                stereo_crossmix( samplesIn, buf, 1, nSamplesFromInput, 1, id );
-            } else if( psEnc->nPrevChannelsInternal == 1 ) {
+            if ( encControl->toMono > 0) {
+                stereo_crossmix( samplesIn, buf, 1, nSamplesFromInput, encControl->toMono, id );
+            } else if( psEnc->nPrevChannelsInternal == 1  || encControl->toMono == -1) {
                 stereo_crossmix( samplesIn, buf, 1, nSamplesFromInput, 0, id );
             } else {
                 for( n = 0; n < nSamplesFromInput; n++ ) {
--- a/src/opus_encoder.c
+++ b/src/opus_encoder.c
@@ -489,10 +489,14 @@
     {
        /* In case the encoder changes its mind on stereo->mono transition */
        st->silk_mode.toMono = -1;
-    } else if (st->stream_channels == 1 && st->prev_channels ==2 && !st->silk_mode.toMono)
+    } else if (st->stream_channels == 1 && st->prev_channels ==2 && st->silk_mode.toMono==0)
     {
-       /* Delay stereo->mono transition so that SILK can do a smooth downmix */
+       /* Delay stereo->mono transition by two frames so that SILK can do a smooth downmix */
        st->silk_mode.toMono=1;
+       st->stream_channels = 2;
+    } else if (st->stream_channels == 1 && st->prev_channels ==2 && st->silk_mode.toMono==1)
+    {
+       st->silk_mode.toMono=2;
        st->stream_channels = 2;
     } else {
        st->silk_mode.toMono=0;