Fix USAC time domain limiter latency at config change.

We have observed quality problems regarding config switching for USAC streams. Crossfading did not consider the USAC time domain limiter latency correctly. The limiter memory still contained the last part of the frame before the config change.
With this patch we were able to improve the quality by moving the limiter processing to the end of the processing chain (crossfade -> DRC -> limiter). By that we don't have to consider the limiter latency at the crossfader anymore and can resolve the quality issue.
Bug: 176246647
Test: atest android.media.cts.DecoderTestAacFormat android.media.cts.DecoderTestXheAac android.media.cts.DecoderTestAacDrc
Change-Id: I0dfd3b76ff2b0daf495ad406283f56a39982ad8f

Change-Id: I26f5da65ef8344602007e180e837820c6a25f173

1 files changed, 14 insertions, 9 deletions

diff --git a/libAACdec/src/aacdecoder.cpp b/libAACdec/src/aacdecoder.cpp
index c6d1832..c18e5e9 100644
--- a/libAACdec/src/aacdecoder.cpp
+++ b/libAACdec/src/aacdecoder.cpp
@@ -568,7 +568,7 @@ static int CProgramConfigElement_Read(HANDLE_FDK_BITSTREAM bs,
   \return  Error code
 */
 LINKSPEC_CPP AAC_DECODER_ERROR CAacDecoder_PrepareCrossFade(
-    const INT_PCM *pTimeData, INT_PCM **pTimeDataFlush, const INT numChannels,
+    const PCM_DEC *pTimeData, PCM_DEC **pTimeDataFlush, const INT numChannels,
     const INT frameSize, const INT interleaved) {
   int i, ch, s1, s2;
   AAC_DECODER_ERROR ErrorStatus;
@@ -584,7 +584,7 @@ LINKSPEC_CPP AAC_DECODER_ERROR CAacDecoder_PrepareCrossFade(
   }
 
   for (ch = 0; ch < numChannels; ch++) {
-    const INT_PCM *pIn = &pTimeData[ch * s1];
+    const PCM_DEC *pIn = &pTimeData[ch * s1];
     for (i = 0; i < TIME_DATA_FLUSH_SIZE; i++) {
       pTimeDataFlush[ch][i] = *pIn;
       pIn += s2;
@@ -606,7 +606,7 @@ LINKSPEC_CPP AAC_DECODER_ERROR CAacDecoder_PrepareCrossFade(
   \return  Error code
 */
 LINKSPEC_CPP AAC_DECODER_ERROR CAacDecoder_ApplyCrossFade(
-    INT_PCM *pTimeData, INT_PCM **pTimeDataFlush, const INT numChannels,
+    PCM_DEC *pTimeData, PCM_DEC **pTimeDataFlush, const INT numChannels,
     const INT frameSize, const INT interleaved) {
   int i, ch, s1, s2;
   AAC_DECODER_ERROR ErrorStatus;
@@ -622,15 +622,15 @@ LINKSPEC_CPP AAC_DECODER_ERROR CAacDecoder_ApplyCrossFade(
   }
 
   for (ch = 0; ch < numChannels; ch++) {
-    INT_PCM *pIn = &pTimeData[ch * s1];
+    PCM_DEC *pIn = &pTimeData[ch * s1];
     for (i = 0; i < TIME_DATA_FLUSH_SIZE; i++) {
       FIXP_SGL alpha = (FIXP_SGL)i
                        << (FRACT_BITS - 1 - TIME_DATA_FLUSH_SIZE_SF);
-      FIXP_DBL time = FX_PCM2FX_DBL(*pIn);
-      FIXP_DBL timeFlush = FX_PCM2FX_DBL(pTimeDataFlush[ch][i]);
+      FIXP_DBL time = PCM_DEC2FIXP_DBL(*pIn);
+      FIXP_DBL timeFlush = PCM_DEC2FIXP_DBL(pTimeDataFlush[ch][i]);
 
-      *pIn = (INT_PCM)(FIXP_PCM)FX_DBL2FX_PCM(
-          timeFlush - fMult(timeFlush, alpha) + fMult(time, alpha));
+      *pIn = FIXP_DBL2PCM_DEC(timeFlush - fMult(timeFlush, alpha) +
+                              fMult(time, alpha));
       pIn += s2;
     }
   }
@@ -753,7 +753,12 @@ LINKSPEC_CPP AAC_DECODER_ERROR CAacDecoder_PreRollExtensionPayloadParse(
     /* We are interested in preroll AUs if an explicit or an implicit config
      * change is signalized in other words if the build up status is set. */
     if (self->buildUpStatus == AACDEC_USAC_BUILD_UP_ON) {
-      self->applyCrossfade |= FDKreadBit(hBs);
+      UCHAR applyCrossfade = FDKreadBit(hBs);
+      if (applyCrossfade) {
+        self->applyCrossfade |= AACDEC_CROSSFADE_BITMASK_PREROLL;
+      } else {
+        self->applyCrossfade &= ~AACDEC_CROSSFADE_BITMASK_PREROLL;
+      }
       FDKreadBit(hBs); /* reserved */
       /* Read num preroll AU's */
       *numPrerollAU = escapedValue(hBs, 2, 4, 0);