Fix mix of panned stereo track to mono

Paul-Licameli · Oct 13, 2023 · a61079e · a61079e
1 parent 7d95e1e
commit a61079e
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Showing 2 changed files with 10 additions and 4 deletions.
diff --git a/libraries/lib-mixer/Mix.cpp b/libraries/lib-mixer/Mix.cpp
@@ -329,9 +329,14 @@ size_t Mixer::Process(const size_t maxToProcess)
       for (size_t j = 0; j < limit; ++j) {
          const auto pFloat = (const float *)mFloatBuffers.GetReadPosition(j);
          auto &sequence = upstream.GetSequence();
-         if (mApplyTrackGains)
-            for (size_t c = 0; c < mNumChannels; ++c)
-               gains[c] = sequence.GetChannelGain(c);
+         if (mApplyTrackGains) {
+            for (size_t c = 0; c < mNumChannels; ++c) {
+               if (mNumChannels > 1)
+                  gains[c] = sequence.GetChannelGain(c);
+               else
+                  gains[c] = sequence.GetChannelGain(j);
+            }
+         }
          const auto flags =
             findChannelFlags(upstream.MixerSpec(j), sequence, j);
          MixBuffers(mNumChannels, flags, gains, *pFloat, mTemp, result);

diff --git a/src/effects/StereoToMono.cpp b/src/effects/StereoToMono.cpp
@@ -160,10 +160,11 @@ bool EffectStereoToMono::ProcessOne(TrackList &outputs,
    assert(outTrack->IsLeader());
    outTrack->ConvertToSampleFormat(floatSample);
 
+   double denominator = track.GetChannelGain(0) + track.GetChannelGain(1);
    while (auto blockLen = mixer.Process()) {
       auto buffer = mixer.GetBuffer();
       for (auto i = 0; i < blockLen; i++)
-         ((float *)buffer)[i] /= 2.0;
+         ((float *)buffer)[i] /= denominator;
 
       // If mixing channels that both had only 16 bit effective format
       // (for example), and no gains or envelopes, still there should be