Basic and untested export option to bounce down to stereo; add encoder test with...

[dcpomatic.git] / src / lib / ffmpeg_encoder.cc

diff --git a/src/lib/ffmpeg_encoder.cc b/src/lib/ffmpeg_encoder.cc
index 52df6c299496c3e316ca6f1b661d229260ad354c..5d06616ee79e9122a14efc8e76ad9bc4c6de34dd 100644 (file)
--- a/src/lib/ffmpeg_encoder.cc
+++ b/src/lib/ffmpeg_encoder.cc
@@ -47,12 +47,11 @@ force_pixel_format (AVPixelFormat, AVPixelFormat out)
        return out;
 }
 
-FFmpegEncoder::FFmpegEncoder (shared_ptr<const Film> film, weak_ptr<Job> job, boost::filesystem::path output, Format format)
+FFmpegEncoder::FFmpegEncoder (shared_ptr<const Film> film, weak_ptr<Job> job, boost::filesystem::path output, Format format, bool mixdown_to_stereo)
        : Encoder (film, job)
        , _video_options (0)
        , _history (1000)
        , _output (output)
-       , _pending_audio (new AudioBuffers (film->audio_channels(), 0))
 {
        switch (format) {
        case FORMAT_PRORES:
@@ -73,6 +72,27 @@ FFmpegEncoder::FFmpegEncoder (shared_ptr<const Film> film, weak_ptr<Job> job, bo
 
        _player->set_always_burn_subtitles (true);
        _player->set_play_referenced ();
+
+       int const ch = film->audio_channels ();
+
+       if (mixdown_to_stereo) {
+               _audio_mapping = AudioMapping (ch, 2);
+               float const overall_gain = 2 / (4 + sqrt(2));
+               float const minus_3dB = 1 / sqrt(2);
+               _audio_mapping.set (dcp::LEFT,   0, overall_gain);
+               _audio_mapping.set (dcp::RIGHT,  1, overall_gain);
+               _audio_mapping.set (dcp::CENTRE, 0, overall_gain * minus_3dB);
+               _audio_mapping.set (dcp::CENTRE, 1, overall_gain * minus_3dB);
+               _audio_mapping.set (dcp::LS,     0, overall_gain);
+               _audio_mapping.set (dcp::RS,     0, overall_gain);
+               _pending_audio.reset (new AudioBuffers (2, 0));
+       } else {
+               _audio_mapping = AudioMapping (ch, ch);
+               _pending_audio.reset (new AudioBuffers (ch, 0));
+               for (int i = 0; i < ch; ++i) {
+                       _audio_mapping.set (i, i, 1);
+               }
+       }
 }
 
 void
@@ -118,8 +138,8 @@ FFmpegEncoder::setup_audio ()
        _audio_codec_context->bit_rate = 256 * 1024;
        _audio_codec_context->sample_fmt = _sample_format;
        _audio_codec_context->sample_rate = _film->audio_frame_rate ();
-       _audio_codec_context->channel_layout = av_get_default_channel_layout (_film->audio_channels ());
-       _audio_codec_context->channels = _film->audio_channels ();
+       _audio_codec_context->channel_layout = av_get_default_channel_layout (_audio_mapping.output_channels ());
+       _audio_codec_context->channels = _audio_mapping.output_channels ();
 }
 
 void
@@ -288,7 +308,7 @@ FFmpegEncoder::video (shared_ptr<PlayerVideo> video, DCPTime time)
 void
 FFmpegEncoder::audio (shared_ptr<AudioBuffers> audio, DCPTime)
 {
-       _pending_audio->append (audio);
+       _pending_audio->append (remap (audio, _audio_mapping.output_channels(), _audio_mapping));
 
        int frame_size = _audio_codec_context->frame_size;
        if (frame_size == 0) {
@@ -309,7 +329,7 @@ FFmpegEncoder::audio_frame (int size)
        AVFrame* frame = av_frame_alloc ();
        DCPOMATIC_ASSERT (frame);
 
-       int const channels = _audio_codec_context->channels;
+       int const channels = _pending_audio->channels();
        DCPOMATIC_ASSERT (channels);
 
        int const buffer_size = av_samples_get_buffer_size (0, channels, size, _audio_codec_context->sample_fmt, 0);