Introduce a fallback override mixer mode.

The fallback override mixer will only engage in case the channel layout changes mid-stream and the new layout is not being accepted by the audio renderer. This is typically the case with WMP/WMC, because they do not like channel re-configurations mid-stream.

When the override mixer is activated, it'll mix the audio to the previous channel layout to ensure playback continues.

Fixes issue 50.

3 files changed, 66 insertions, 17 deletions

diff --git a/decoder/LAVAudio/LAVAudio.cpp b/decoder/LAVAudio/LAVAudio.cpp
index ed36bba5..ed975428 100644
--- a/decoder/LAVAudio/LAVAudio.cpp
+++ b/decoder/LAVAudio/LAVAudio.cpp
@@ -80,6 +80,7 @@ CLAVAudio::CLAVAudio(LPUNKNOWN pUnk, HRESULT* phr)
   , m_bChannelMappingRequired(FALSE)
   , m_bFindDTSInPCM(FALSE)
   , m_bFallback16Int(FALSE)
+  , m_dwOverrideMixer(0)
   , m_bNeedSyncpoint(FALSE)
   , m_dRate(1.0)
   , m_bInputPadded(FALSE)
@@ -88,6 +89,7 @@ CLAVAudio::CLAVAudio(LPUNKNOWN pUnk, HRESULT* phr)
   , m_bMixingSettingsChanged(FALSE)
   , m_fMixingClipThreshold(0.0f)
   , m_bHasVideo(TRUE)
+  , m_dwRemixLayout(0)
 {
 #ifdef DEBUG
   DbgSetModuleLevel (LOG_CUSTOM1, DWORD_MAX); // FFMPEG messages use custom1
@@ -1260,6 +1262,8 @@ HRESULT CLAVAudio::ffmpeg_init(CodecID codec, const void *format, const GUID for
 
   m_bFindDTSInPCM = (codec == CODEC_ID_PCM_S16LE && m_settings.bFormats[Codec_DTS]);
   m_bFallback16Int = FALSE;
+  m_dwOverrideMixer = 0;
+  m_bMixingSettingsChanged = TRUE;
 
   return S_OK;
 }
@@ -2083,13 +2087,55 @@ HRESULT CLAVAudio::Deliver(BufferDetails &buffer)
   if(hr == S_OK) {
     hr = m_pOutput->GetConnected()->QueryAccept(&mt);
     DbgLog((LOG_TRACE, 1, L"Sending new Media Type (QueryAccept: %0#.8x)", hr));
-    if (hr != S_OK && buffer.sfFormat != SampleFormat_16) {
-      mt = CreateMediaType(SampleFormat_16, buffer.dwSamplesPerSec, buffer.wChannels, buffer.dwChannelMask, 16);
-      hr = m_pOutput->GetConnected()->QueryAccept(&mt);
-      if (hr == S_OK) {
-        DbgLog((LOG_TRACE, 1, L"-> 16-bit fallback type accepted"));
-        ConvertSampleFormat(&buffer, SampleFormat_16);
-        m_bFallback16Int = TRUE;
+    if (hr != S_OK) {
+      if (buffer.sfFormat != SampleFormat_16) {
+        mt = CreateMediaType(SampleFormat_16, buffer.dwSamplesPerSec, buffer.wChannels, buffer.dwChannelMask, 16);
+        hr = m_pOutput->GetConnected()->QueryAccept(&mt);
+        if (hr == S_OK) {
+          DbgLog((LOG_TRACE, 1, L"-> 16-bit fallback type accepted"));
+          ConvertSampleFormat(&buffer, SampleFormat_16);
+          m_bFallback16Int = TRUE;
+        }
+      }
+      // If a 16-bit fallback isn't enough, try to retain current channel layout
+      if (hr != S_OK) {
+        WAVEFORMATEX* wfeCurrent = (WAVEFORMATEX*)m_pOutput->CurrentMediaType().Format();
+        WORD wChannels = wfeCurrent->nChannels;
+        DWORD dwChannelMask = 0;
+        if (wfeCurrent->wFormatTag == WAVE_FORMAT_EXTENSIBLE) {
+          WAVEFORMATEXTENSIBLE *wfex = (WAVEFORMATEXTENSIBLE *)wfeCurrent;
+          dwChannelMask = wfex->dwChannelMask;
+        } else {
+          dwChannelMask = wChannels == 2 ? (SPEAKER_FRONT_LEFT|SPEAKER_FRONT_RIGHT) : SPEAKER_FRONT_CENTER;
+        }
+        mt = CreateMediaType(buffer.sfFormat, buffer.dwSamplesPerSec, wChannels, dwChannelMask, buffer.wBitsPerSample);
+        hr = m_pOutput->GetConnected()->QueryAccept(&mt);
+        if (hr == S_OK) {
+          DbgLog((LOG_TRACE, 1, L"-> Override Mixing to layout 0x%x", dwChannelMask));
+          m_dwOverrideMixer = dwChannelMask;
+          m_bMixingSettingsChanged = TRUE;
+          LAVAudioSampleFormat sf = buffer.sfFormat;
+          // Mix to the new layout
+          PerformMixing(&buffer);
+          // Convert to old sample format, if required
+          if (buffer.sfFormat != sf) {
+            ConvertSampleFormat(&buffer, sf);
+          }
+        } else {
+          // If current channel layout alone wasn't enough, also go 16-bit
+          mt = CreateMediaType(SampleFormat_16, buffer.dwSamplesPerSec, wChannels, dwChannelMask, 16);
+          hr = m_pOutput->GetConnected()->QueryAccept(&mt);
+          if (hr == S_OK) {
+            DbgLog((LOG_TRACE, 1, L"-> Override Mixing to layout 0x%x with 16-bit fallback type", dwChannelMask));
+            m_dwOverrideMixer = dwChannelMask;
+            m_bMixingSettingsChanged = TRUE;
+            // Mix to new layout
+            PerformMixing(&buffer);
+            // Convert to 16-bit
+            ConvertSampleFormat(&buffer, SampleFormat_16);
+            m_bFallback16Int = TRUE;
+          }
+        }
       }
     }
     m_pOutput->SetMediaType(&mt);
diff --git a/decoder/LAVAudio/LAVAudio.h b/decoder/LAVAudio/LAVAudio.h
index 38b3b199..68ac5879 100644
--- a/decoder/LAVAudio/LAVAudio.h
+++ b/decoder/LAVAudio/LAVAudio.h
@@ -263,6 +263,7 @@ private:
   GrowableArray<BYTE>  m_buff;           // Input Buffer
   LAVAudioSampleFormat     m_DecodeFormat;  // Number of bits in the samples
   BOOL                 m_bFallback16Int;
+  DWORD                m_dwOverrideMixer;
 
   BOOL                 m_bSampleSupport[SampleFormat_NB];
 
diff --git a/decoder/LAVAudio/PostProcessor.cpp b/decoder/LAVAudio/PostProcessor.cpp
index c3103736..87947c8b 100644
--- a/decoder/LAVAudio/PostProcessor.cpp
+++ b/decoder/LAVAudio/PostProcessor.cpp
@@ -554,8 +554,10 @@ HRESULT CLAVAudio::PerformMixing(BufferDetails *buffer)
 {
   int ret = 0;
 
+  DWORD dwMixingLayout = m_dwOverrideMixer ? m_dwOverrideMixer : m_settings.MixingLayout;
+
   // Check if we need mixing, either already in target mask or in stereo (no downmixing from stereo)
-  if (buffer->dwChannelMask == m_settings.MixingLayout || (buffer->wChannels <= 2 && (m_settings.MixingFlags & LAV_MIXING_FLAG_UNTOUCHED_STEREO)))
+  if (buffer->dwChannelMask == dwMixingLayout || (buffer->wChannels <= 2 && (m_settings.MixingFlags & LAV_MIXING_FLAG_UNTOUCHED_STEREO) && !m_dwOverrideMixer))
     return S_FALSE;
 
   // Sadly, we need to convert this, avresample has no 24-bit mode
@@ -563,7 +565,7 @@ HRESULT CLAVAudio::PerformMixing(BufferDetails *buffer)
     ConvertSampleFormat(buffer, SampleFormat_32);
   }
 
-  if (buffer->dwChannelMask != m_DecodeLayoutSanified || (!m_avrContext && !m_bAVResampleFailed) || m_bMixingSettingsChanged) {
+  if (buffer->dwChannelMask != m_DecodeLayoutSanified || (!m_avrContext && !m_bAVResampleFailed) || m_bMixingSettingsChanged || m_dwRemixLayout != dwMixingLayout) {
     m_bAVResampleFailed = FALSE;
     m_bMixingSettingsChanged = FALSE;
     if (m_avrContext) {
@@ -587,20 +589,20 @@ HRESULT CLAVAudio::PerformMixing(BufferDetails *buffer)
     av_opt_set_int(m_avrContext, "in_channel_layout", buffer->dwChannelMask, 0);
     av_opt_set_int(m_avrContext, "in_sample_fmt", get_ff_sample_fmt(buffer->sfFormat), 0);
 
-    av_opt_set_int(m_avrContext, "out_channel_layout", m_settings.MixingLayout, 0);
+    av_opt_set_int(m_avrContext, "out_channel_layout", dwMixingLayout, 0);
     av_opt_set_int(m_avrContext, "out_sample_fmt", get_ff_sample_fmt(m_sfRemixFormat), 0);
 
     // Create Matrix
     int in_ch = buffer->wChannels;
-    int out_ch = av_get_channel_layout_nb_channels(m_settings.MixingLayout);
+    int out_ch = av_get_channel_layout_nb_channels(dwMixingLayout);
     double *matrix_dbl = (double *)av_mallocz(in_ch * out_ch * sizeof(*matrix_dbl));
 
     const double center_mix_level = (double)m_settings.MixingCenterLevel / 10000.0 / M_SQRT1_2;
     const double surround_mix_level = (double)m_settings.MixingSurroundLevel / 10000.0;
     const double lfe_mix_level = (double)m_settings.MixingLFELevel / 10000.0;
-    ret = avresample_build_matrix(buffer->dwChannelMask, m_settings.MixingLayout, center_mix_level, surround_mix_level, lfe_mix_level, bNormalize, matrix_dbl, in_ch, (AVMatrixEncoding)m_settings.MixingMode);
+    ret = avresample_build_matrix(buffer->dwChannelMask, dwMixingLayout, center_mix_level, surround_mix_level, lfe_mix_level, bNormalize, matrix_dbl, in_ch, (AVMatrixEncoding)m_settings.MixingMode);
     if (ret < 0) {
-      DbgLog((LOG_ERROR, 10, L"avresample_build_matrix failed, layout in: %x, out: %x, sample fmt in: %d, out: %d", buffer->dwChannelMask, m_settings.MixingLayout, buffer->sfFormat, m_sfRemixFormat));
+      DbgLog((LOG_ERROR, 10, L"avresample_build_matrix failed, layout in: %x, out: %x, sample fmt in: %d, out: %d", buffer->dwChannelMask, dwMixingLayout, buffer->sfFormat, m_sfRemixFormat));
       av_free(matrix_dbl);
       goto setuperr;
     }
@@ -609,18 +611,18 @@ HRESULT CLAVAudio::PerformMixing(BufferDetails *buffer)
     ret = avresample_set_matrix(m_avrContext, matrix_dbl, in_ch);
     av_free(matrix_dbl);
     if (ret < 0) {
-      DbgLog((LOG_ERROR, 10, L"avresample_set_matrix failed, layout in: %x, out: %x, sample fmt in: %d, out: %d", buffer->dwChannelMask, m_settings.MixingLayout, buffer->sfFormat, m_sfRemixFormat));
+      DbgLog((LOG_ERROR, 10, L"avresample_set_matrix failed, layout in: %x, out: %x, sample fmt in: %d, out: %d", buffer->dwChannelMask, dwMixingLayout, buffer->sfFormat, m_sfRemixFormat));
       goto setuperr;
     }
 
     // Open Resample Context
     ret = avresample_open(m_avrContext);
     if (ret < 0) {
-      DbgLog((LOG_ERROR, 10, L"avresample_open failed, layout in: %x, out: %x, sample fmt in: %d, out: %d", buffer->dwChannelMask, m_settings.MixingLayout, buffer->sfFormat, m_sfRemixFormat));
+      DbgLog((LOG_ERROR, 10, L"avresample_open failed, layout in: %x, out: %x, sample fmt in: %d, out: %d", buffer->dwChannelMask, dwMixingLayout, buffer->sfFormat, m_sfRemixFormat));
       goto setuperr;
     }
 
-    m_dwRemixLayout = m_settings.MixingLayout;
+    m_dwRemixLayout = dwMixingLayout;
   }
 
   if (!m_avrContext)
@@ -683,7 +685,7 @@ HRESULT CLAVAudio::PostProcess(BufferDetails *buffer)
     buffer->dwChannelMask = get_channel_mask(buffer->wChannels);
   }
 
-  if (m_settings.MixingEnabled) {
+  if (m_settings.MixingEnabled || m_dwOverrideMixer) {
     PerformMixing(buffer);
   }
   // Remap to standard configurations, if requested