decoder: fixed longstanding audio sync issue

Wow this has probably been a bug for 3 years straight

app/codec/decoder.cpp

@@ -217,14 +217,11 @@ DecoderPtr Decoder::CreateFromID(const QString &id)
 
 int64_t Decoder::GetTimeInTimebaseUnits(const rational &time, const rational &timebase, int64_t start_time)
 {
-  int64_t t = Timecode::time_to_timestamp(time, timebase);
-  t += start_time;
-  return t;
+  return Timecode::time_to_timestamp(time, timebase);
 }
 
 rational Decoder::GetTimestampInTimeUnits(int64_t time, const rational &timebase, int64_t start_time)
 {
-  time -= start_time;
   return Timecode::timestamp_to_time(time, timebase);
 }
 
@@ -294,10 +291,13 @@ bool Decoder::ConformAudioInternal(const QVector<QString> &filenames, const Audi
   return false;
 }
 
-bool Decoder::RetrieveAudioFromConform(SampleBuffer &sample_buffer, const QVector<QString> &conform_filenames, const TimeRange& range, LoopMode loop_mode, const AudioParams &input_params)
+bool Decoder::RetrieveAudioFromConform(SampleBuffer &sample_buffer, const QVector<QString> &conform_filenames, TimeRange range, LoopMode loop_mode, const AudioParams &input_params)
 {
   PlanarFileDevice input;
   if (input.open(conform_filenames, QFile::ReadOnly)) {
+    // Offset range by audio start offset
+    range -= GetAudioStartOffset();
+
     qint64 read_index = input_params.time_to_bytes(range.in()) / input_params.channel_count();
     qint64 write_index = 0;
 

app/codec/decoder.h

@@ -297,6 +297,8 @@ protected:
   static int64_t GetTimeInTimebaseUnits(const rational& time, const rational& timebase, int64_t start_time);
   static rational GetTimestampInTimeUnits(int64_t time, const rational& timebase, int64_t start_time);
 
+  virtual rational GetAudioStartOffset() const { return 0; }
+
 signals:
   /**
    * @brief While indexing, this signal will provide progress as a percentage (0-100 inclusive) if
@@ -307,7 +309,7 @@ signals:
 private:
   void UpdateLastAccessed();
 
-  bool RetrieveAudioFromConform(SampleBuffer &sample_buffer, const QVector<QString> &conform_filenames, const TimeRange &range, LoopMode loop_mode, const AudioParams &params);
+  bool RetrieveAudioFromConform(SampleBuffer &sample_buffer, const QVector<QString> &conform_filenames, TimeRange range, LoopMode loop_mode, const AudioParams &params);
 
   CodecStream stream_;
 

app/codec/ffmpeg/ffmpegdecoder.cpp

@@ -143,7 +143,7 @@ bool FFmpegDecoder::OpenInternal()
 
 TexturePtr FFmpegDecoder::RetrieveVideoInternal(const RetrieveVideoParams &p)
 {
-  if (AVFramePtr f = RetrieveFrame(p.time, p.cancelled)) {
+  if (AVFramePtr f = RetrieveFrame(p.time, p.src_interlacing, p.cancelled)) {
     if (p.cancelled && p.cancelled->IsCancelled()) {
       return nullptr;
     }
@@ -311,6 +311,16 @@ void FFmpegDecoder::CloseInternal()
   native_output_pix_fmt_ = VideoParams::kFormatInvalid;
 }
 
+rational FFmpegDecoder::GetAudioStartOffset() const
+{
+  AVStream *s = this->instance_.avstream();
+  if (s) {
+    return rational(s->start_time * s->time_base.num, s->time_base.den);
+  } else {
+    return 0;
+  }
+}
+
 QString FFmpegDecoder::id() const
 {
   return QStringLiteral("ffmpeg");
@@ -787,10 +797,14 @@ void FFmpegDecoder::ClearFrameCache()
   }
 }
 
-AVFramePtr FFmpegDecoder::RetrieveFrame(const rational& time, CancelAtom *cancelled)
+AVFramePtr FFmpegDecoder::RetrieveFrame(const rational& time, VideoParams::Interlacing interlacing, CancelAtom *cancelled)
 {
   int64_t target_ts = GetTimeInTimebaseUnits(time, instance_.avstream()->time_base, instance_.avstream()->start_time);
 
+  if (interlacing != VideoParams::kInterlaceNone) {
+    target_ts *= 2;
+  }
+
   const int64_t min_seek = -instance_.avstream()->start_time;
   int64_t seek_ts = std::max(min_seek, target_ts - MaximumQueueSize());
   bool still_seeking = false;

app/codec/ffmpeg/ffmpegdecoder.h

@@ -67,6 +67,8 @@ protected:
   virtual bool ConformAudioInternal(const QVector<QString>& filenames, const AudioParams &params, CancelAtom *cancelled) override;
   virtual void CloseInternal() override;
 
+  virtual rational GetAudioStartOffset() const override;
+
 private:
   class Instance
   {
@@ -148,7 +150,7 @@ private:
 
   void ClearFrameCache();
 
-  AVFramePtr RetrieveFrame(const rational &time, CancelAtom *cancelled);
+  AVFramePtr RetrieveFrame(const rational &time, VideoParams::Interlacing interlacing, CancelAtom *cancelled);
 
   void RemoveFirstFrame();