+double
+FFmpegDecoder::frame_time () const
+{
+ return av_frame_get_best_effort_timestamp(_frame) * av_q2d (_format_context->streams[_video_stream]->time_base);
+}
+
+void
+FFmpegDecoder::decode_audio_packet ()
+{
+ /* Audio packets can contain multiple frames, so we may have to call avcodec_decode_audio4
+ several times.
+ */
+
+ AVPacket copy_packet = _packet;
+
+ while (copy_packet.size > 0) {
+
+ int frame_finished;
+ int const decode_result = avcodec_decode_audio4 (_audio_codec_context, _frame, &frame_finished, ©_packet);
+ if (decode_result >= 0 && frame_finished) {
+
+ /* Where we are in the source, in seconds */
+ double const source_pts_seconds = av_q2d (_format_context->streams[copy_packet.stream_index]->time_base)
+ * av_frame_get_best_effort_timestamp(_frame);
+
+ /* We only decode audio if we've had our first video packet through, and if it
+ was before this packet. Until then audio is thrown away.
+ */
+
+ if ((_first_video && _first_video.get() <= source_pts_seconds) || !_decode_video) {
+
+ if (!_first_audio && _decode_video) {
+ _first_audio = source_pts_seconds;
+
+ /* This is our first audio frame, and if we've arrived here we must have had our
+ first video frame. Push some silence to make up any gap between our first
+ video frame and our first audio.
+ */
+
+ /* frames of silence that we must push */
+ int const s = rint ((_first_audio.get() - _first_video.get()) * _ffmpeg_content->audio_frame_rate ());
+
+ _film->log()->log (
+ String::compose (
+ N_("First video at %1, first audio at %2, pushing %3 audio frames of silence for %4 channels (%5 bytes per sample)"),
+ _first_video.get(), _first_audio.get(), s, _ffmpeg_content->audio_channels(), bytes_per_audio_sample()
+ )
+ );
+
+ if (s) {
+ shared_ptr<AudioBuffers> audio (new AudioBuffers (_ffmpeg_content->audio_channels(), s));
+ audio->make_silent ();
+ Audio (audio);
+ }
+ }
+
+ int const data_size = av_samples_get_buffer_size (
+ 0, _audio_codec_context->channels, _frame->nb_samples, audio_sample_format (), 1
+ );
+
+ assert (_audio_codec_context->channels == _ffmpeg_content->audio_channels());
+ Audio (deinterleave_audio (_frame->data, data_size));
+ }
+ }
+
+ if (decode_result >= 0) {
+ copy_packet.data += decode_result;
+ copy_packet.size -= decode_result;
+ }
+ }
+}