decoder/ffmpeg: skip unwanted samples after seeking

When seeking to the beginning of a packet, skip the samples that come
before the desired time stamp.
This commit is contained in:
Max Kellermann 2015-06-19 18:02:10 +02:00
parent d11e2724c4
commit 327a8e6c59
2 changed files with 50 additions and 5 deletions

2
NEWS
View File

@ -2,6 +2,8 @@ ver 0.19.10 (not yet released)
* input * input
- curl: fix deadlock on small responses - curl: fix deadlock on small responses
- smbclient: fix DFF playback - smbclient: fix DFF playback
* decoder
- ffmpeg: improve seeking accuracy
* encoder * encoder
- opus: fix bogus granulepos - opus: fix bogus granulepos
* neighbor * neighbor

View File

@ -321,18 +321,44 @@ StreamRelativePts(const AVPacket &packet, const AVStream &stream)
return pts - start; return pts - start;
} }
/**
* Convert a non-negative stream-relative time stamp in
* AVStream::time_base units to a PCM frame number.
*/
gcc_pure
static uint64_t
PtsToPcmFrame(uint64_t pts, const AVStream &stream,
const AVCodecContext &codec_context)
{
return av_rescale_q(pts, stream.time_base, codec_context.time_base);
}
/**
* @param min_frame skip all data before this PCM frame number; this
* is used after seeking to skip data in an AVPacket until the exact
* desired time stamp has been reached
*/
static DecoderCommand static DecoderCommand
ffmpeg_send_packet(Decoder &decoder, InputStream &is, ffmpeg_send_packet(Decoder &decoder, InputStream &is,
const AVPacket *packet, const AVPacket *packet,
AVCodecContext *codec_context, AVCodecContext *codec_context,
const AVStream *stream, const AVStream *stream,
AVFrame *frame, AVFrame *frame,
uint64_t min_frame, size_t pcm_frame_size,
uint8_t **buffer, int *buffer_size) uint8_t **buffer, int *buffer_size)
{ {
size_t skip_bytes = 0;
const auto pts = StreamRelativePts(*packet, *stream); const auto pts = StreamRelativePts(*packet, *stream);
if (pts >= 0) { if (pts >= 0) {
decoder_timestamp(decoder, if (min_frame > 0) {
time_from_ffmpeg(pts, stream->time_base)); auto cur_frame = PtsToPcmFrame(pts, *stream,
*codec_context);
if (cur_frame < min_frame)
skip_bytes = pcm_frame_size * (min_frame - cur_frame);
} else
decoder_timestamp(decoder,
time_from_ffmpeg(pts, stream->time_base));
} }
AVPacket packet2 = *packet; AVPacket packet2 = *packet;
@ -368,8 +394,20 @@ ffmpeg_send_packet(Decoder &decoder, InputStream &is,
if (audio_size <= 0) if (audio_size <= 0)
continue; continue;
const uint8_t *data = output_buffer;
if (skip_bytes > 0) {
if (skip_bytes >= size_t(audio_size)) {
skip_bytes -= audio_size;
continue;
}
data += skip_bytes;
audio_size -= skip_bytes;
skip_bytes = 0;
}
cmd = decoder_data(decoder, is, cmd = decoder_data(decoder, is,
output_buffer, audio_size, data, audio_size,
codec_context->bit_rate / 1000); codec_context->bit_rate / 1000);
} }
return cmd; return cmd;
@ -573,6 +611,8 @@ ffmpeg_decode(Decoder &decoder, InputStream &input)
uint8_t *interleaved_buffer = nullptr; uint8_t *interleaved_buffer = nullptr;
int interleaved_buffer_size = 0; int interleaved_buffer_size = 0;
uint64_t min_frame = 0;
DecoderCommand cmd; DecoderCommand cmd;
do { do {
AVPacket packet; AVPacket packet;
@ -580,13 +620,15 @@ ffmpeg_decode(Decoder &decoder, InputStream &input)
/* end of file */ /* end of file */
break; break;
if (packet.stream_index == audio_stream) if (packet.stream_index == audio_stream) {
cmd = ffmpeg_send_packet(decoder, input, cmd = ffmpeg_send_packet(decoder, input,
&packet, codec_context, &packet, codec_context,
av_stream, av_stream,
frame, frame,
min_frame, audio_format.GetFrameSize(),
&interleaved_buffer, &interleaved_buffer_size); &interleaved_buffer, &interleaved_buffer_size);
else min_frame = 0;
} else
cmd = decoder_get_command(decoder); cmd = decoder_get_command(decoder);
av_free_packet(&packet); av_free_packet(&packet);
@ -606,6 +648,7 @@ ffmpeg_decode(Decoder &decoder, InputStream &input)
decoder_seek_error(decoder); decoder_seek_error(decoder);
else { else {
avcodec_flush_buffers(codec_context); avcodec_flush_buffers(codec_context);
min_frame = decoder_seek_where_frame(decoder);
decoder_command_finished(decoder); decoder_command_finished(decoder);
} }
} }