Method Process

modules/import-export/mod-opus/ExportOpus.cpp:765–886

}

ExportResult OpusExportProcessor::Process(ExportProcessorDelegate& delegate)
{
   delegate.SetStatusString(context.status);

   auto exportResult = ExportResult::Success;

   int64_t granulePos = 0;

   int32_t latencyLeft = context.opus.preskip;

   while (exportResult == ExportResult::Success)
   {
      auto samplesThisRun = context.mixer->Process();

      if (samplesThisRun == 0)
         break;

      auto mixedAudioBuffer =
         reinterpret_cast<const float*>(context.mixer->GetBuffer());

      // bestFrameSize <= context.opus.frameSize by design
      auto bestFrameSize = GetBestFrameSize(samplesThisRun);

      if (samplesThisRun < bestFrameSize)
      {
         // Opus expects that the full frame is passed to the encoder, fill missing data with zeroes
         context.encodeBuffer.resize(bestFrameSize * context.numChannels);

         std::copy(
            mixedAudioBuffer, mixedAudioBuffer + samplesThisRun * context.numChannels,
            context.encodeBuffer.begin());

         std::fill(
            context.encodeBuffer.begin() + samplesThisRun * context.numChannels,
            context.encodeBuffer.begin() + bestFrameSize * context.numChannels,
            0);

         mixedAudioBuffer = context.encodeBuffer.data();

         auto zeroesCount = bestFrameSize - int32_t(samplesThisRun);

         if (zeroesCount < latencyLeft)
            samplesThisRun += zeroesCount;
         else
            samplesThisRun += latencyLeft;

         // Reduce the latency by the number of zeroes pushed (potentially
         // removing the need to flush the encoder)
         latencyLeft = std::max(0, latencyLeft - zeroesCount);
      }

      auto result = opus_multistream_encode_float(
         context.opus.encoder, mixedAudioBuffer, bestFrameSize,
         context.ogg.audioStreamPacket.GetBuffer(),
         context.ogg.audioStreamPacket.GetBufferSize());

      if (result < 0)
         FailExport(XO("Failed to encode input buffer"), result);