Hi,
Am 27.07.2010 12:15, schrieb august:
>
> So, I noticed that when I do bgav_seek(), it seeks on both audio and
> video. However, when I seek on bgav_seek_audio() or bgav_seek_video() using
> the sample accurate api, it only seeks on the audio or video file
> pointers. Is that right?
Yes. In sample accurate mode all streams can be positioned independently.
In this case, bgav_seek() just calls bgav_seek_[audio|video|subtitle]() for
all active streams.
> I was just wondering if the int64_t time argument for bgav_seek_video()
> is the same thing as a gavl_time_t. I see they are both int64_t, but
> do they mean the same thing?
No. gavl_time_t is *always* microsecond scale, while the int64_t for the
per-stream seek functions has the timescale of that stream.
> In other words, can I do:
> gavl_time_t gt = gavl_samples_to_time( samplerate, seekto ) ;
> bgav_seek_audio( file , 0, seekto );
> bgav_seek_video( file, 0 , gt );
No. If seekto is the sample position, call
int64_t video_time = gavl_time_rescale(audio_format.samplerate,
video_format.timescale, seekto);
But that's suboptimal because audio samples have a finer granularity than
video frames. The case below has better A/V sync after seeking.
> Also:
>
> gavl_time_t gt = gavl_frames_to_time (timescale, frame_duration, seekto );
> bgav_seek_video(file , 0, gt );
> bgav_seek_audio( file , 0, gavl_time_to_samples( samplerate, gt ) );
No, if seekto is the frame number, do:
int64_t video_time = seekto * frame_duration;
bgav_seek_video(file , 0, video_time );
bgav_seek_audio( file , 0, gavl_time_rescale(video_format.timescale,
audio_format.samplerate, video_time) );
And, as noted above it's better to seek to a *video* position first and then
synchronize the audio stream to that position than vice versa.
Also note, that what you probably want to do is already implemented in
bgav_seek() and bgav_seek_scaled(), so maybe it's easier to use these functions
instead.
> thanks-august.
Burkhard
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