Allow 5.0 audio playback on hardware not supporting it.

ALSA doesn't support 5.0 audio and myth could only upmix mono and stereo. Extend upmixer to work with 5.0 audio.
Based on a patch by Mark Spieth
Fixes #9989

Backport SHA1:909b444

Author: jyavenard

mythtv/libs/libmyth/audiooutputbase.cpp

@@ -33,6 +33,10 @@
 #define QUALITY_MEDIUM      1
 #define QUALITY_HIGH        2
 
+// 1,2 and 5 channels are currently valid for upmixing if required
+#define UPMIX_CHANNEL_MASK ((1<<1)|(1<<2)|(1<<5))
+#define IS_VALID_UPMIX_CHANNEL(ch) ((1 << (ch)) & UPMIX_CHANNEL_MASK)
+
 static const char *quality_string(int q)
 {
     switch(q) {
@@ -459,13 +463,15 @@ void AudioOutputBase::Reconfigure(const AudioSettings &orig_settings)
         }
         else
         {
-            // if source was mono, and hardware doesn't support it
-            // we will upmix it to stereo (can safely assume hardware supports
-            // stereo)
-            if (lsource_channels == 1 &&
-                !output_settings->IsSupportedChannels(1))
+            // if source was mono or 5.0, and hardware doesn't support it
+            // we will upmix it respectively to stereo or 5.1
+            // (can safely assume hardware supports stereo)
+            // Ideally we should be able to upmix any channels configuration
+            if ((lsource_channels == 1 || lsource_channels == 5) &&
+                !output_settings->IsSupportedChannels(lsource_channels))
             {
-                configured_channels = 2;
+                    // 1 => 2, 5 => 6
+                configured_channels = lsource_channels + 1;
             }
             else
                 configured_channels = (upmix_default && lsource_channels == 2) ?
@@ -480,8 +486,8 @@ void AudioOutputBase::Reconfigure(const AudioSettings &orig_settings)
             lreenc = true;
         }
 
-        // Enough channels? Upmix if not, but only from mono/stereo to 5.1
-        if (settings.channels <= 2 && settings.channels < configured_channels)
+        // Enough channels? Upmix if not, but only from mono/stereo/5.0 to 5.1
+        if (IS_VALID_UPMIX_CHANNEL(settings.channels) && settings.channels < configured_channels)
         {
             int conf_channels = (configured_channels > 6) ?
                                                     6 : configured_channels;
@@ -736,8 +742,10 @@ void AudioOutputBase::Reconfigure(const AudioSettings &orig_settings)
     VolumeBase::SyncVolume();
     VolumeBase::UpdateVolume();
 
-    // Upmix Stereo to 5.1
-    if (needs_upmix && source_channels == 2 && configured_channels > 2)
+    // Upmix Stereo or 5.0 to 5.1
+    if (needs_upmix &&
+        (source_channels == 2 || source_channels == 5) &&
+        configured_channels > 2)
     {
         surround_mode = gCoreContext->GetNumSetting("AudioUpmixType", QUALITY_HIGH);
         if ((upmixer = new FreeSurround(samplerate, source == AUDIOOUTPUT_VIDEO,

mythtv/libs/libmythfreesurround/freesurround.cpp

@@ -137,7 +137,8 @@ FreeSurround::FreeSurround(uint srate, bool moviemode, SurroundMode smode) :
     out_count(0),
     processed(true),
     processed_size(0),
-    surround_mode(smode)
+    surround_mode(smode),
+    latency_frames(0)
 {
     VERBOSE(VB_AUDIO+VB_EXTRA,
             QString("FreeSurround::FreeSurround rate %1 moviemode %2")
@@ -161,6 +162,7 @@ FreeSurround::FreeSurround(uint srate, bool moviemode, SurroundMode smode) :
             break;
         case SurroundModeActiveLinear:
             params.steering = 1;
+            latency_frames = block_size/2;
             break;
         default:
             break;
@@ -243,10 +245,28 @@ uint FreeSurround::putFrames(void* buffer, uint numFrames, uint numChannels)
                         bufs->ls[ic]  = bufs->rs[ic] = (lt-rt) * center_level;
                     }
                     break;
+                case 5:
+                    for (i = 0; i < numFrames && ic < bs; i++,ic++)
+                    {
+                        float lt      = *samples++;
+                        float rt      = *samples++;
+                        float c       = *samples++;
+                        float lfe     = (lt+rt) * center_level;
+                        float ls      = *samples++;
+                        float rs      = *samples++;
+                        bufs->l[ic]   = lt;
+                        bufs->lfe[ic] = lfe;
+                        bufs->c[ic]   = c;
+                        bufs->r[ic]   = rt;
+                        bufs->ls[ic]  = ls;
+                        bufs->rs[ic]  = rs;
+                    }
+                    break;
             }
             in_count = 0;
             out_count = processed_size = ic;
             processed = false;
+            latency_frames = 0;
             break;
 
         default:
@@ -268,23 +288,52 @@ uint FreeSurround::putFrames(void* buffer, uint numFrames, uint numChannels)
                         *rt++ = *samples++;
                     }
                     break;
+                case 5:
+                    // 5 ch is always passive mode,
+                    for (i = 0; i < numFrames && ic < bs; i++,ic++)
+                    {
+                        float l       = *samples++;
+                        float r       = *samples++;
+                        float c       = *samples++;
+                        float lfe     = (l+r) * center_level;
+                        float ls      = *samples++;
+                        float rs      = *samples++;
+                        bufs->l[ic]   = l;
+                        bufs->lfe[ic] = lfe;
+                        bufs->c[ic]   = c;
+                        bufs->r[ic]   = r;
+                        bufs->ls[ic]  = ls;
+                        bufs->rs[ic]  = rs;
+                    }
+                    process = false;
+                    break;
             }
-            ic += numFrames;
-            processed = process;
-            if (ic != bs)
-            {
-                // dont modify unless no processing is to be done
-                // for audiotime consistency
-                in_count = ic;
-                break;
-            }
-            // process_block takes some time so dont update in and out count
-            // before its finished so that Audiotime is correctly calculated
             if (process)
+            {
+                ic += numFrames;
+                if (ic != bs)
+                {
+                    // dont modify unless no processing is to be done
+                    // for audiotime consistency
+                    in_count = ic;
+                    break;
+                }
+                processed = process;
+                // process_block takes some time so dont update in and out count
+                // before its finished so that Audiotime is correctly calculated
                 process_block();
-            in_count = 0;
-            out_count = bs;
-            processed_size = bs;
+                in_count = 0;
+                out_count = bs;
+                processed_size = bs;
+                latency_frames = block_size/2;
+            }
+            else
+            {
+                in_count = 0;
+                out_count = processed_size = ic;
+                processed = false;
+                latency_frames = 0;
+            }
             break;
     }
 
@@ -386,9 +435,9 @@ void FreeSurround::process_block()
 long long FreeSurround::getLatency() 
 {
     // returns in usec
-    if (surround_mode == SurroundModePassive)
+    if (latency_frames = 0)
         return 0;
-    return decoder ? ((block_size/2 + in_count)*1000000)/(2*srate) : 0;
+    return decoder ? ((latency_frames + in_count)*1000000)/(2*srate) : 0;
 }
 
 void FreeSurround::flush()

mythtv/libs/libmythfreesurround/freesurround.h

@@ -85,6 +85,7 @@ class FreeSurround
     bool processed;             // whether processing is enabled for latency calc
     int processed_size;                 // amount processed
     SurroundMode surround_mode;         // 1 of 3 surround modes supported
+    int latency_frames;                 // number of frames of incurred latency
 };
 
 #endif