[Libav-user] Samples of silence after a av_seek_frame

Steve musicspeedchanger at gmail.com
Sun Sep 11 20:39:10 EEST 2016

Steve wrote
> I'm using ffmpeg audio decoding to create a gapless audio loop. I call
> av_seek_frame (with AVSEEK_FLAG_BACKWARD) to seek to my desired time, and
> call avcode_flush_buffers after. It seems the first decoded frame in the
> audio stream after the seek contains a few samples of silence or near
> silence, thus making the loop not gapless.
> If I skip an arbitrary amount of samples, the gap disappears. I've tried
> bypassing any swr_convert resampling with same results and also using the
> deprecated avcodec_decode_audio4 instead of the
> avcodec_send_packet/av_read_frame scheme.
> Is there a way to know how many samples I need to skip so I exactly hit
> the
> actual audio data, or prevent ffmpeg from having these filler samples in
> AVFrame->data after the seek?
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I should also mention I know that the av_seek_frame won't seek to the exact
time requested, it's on the packet boundary. I can account for the number of
samples I need to skip to get to the exact time, but when the number of
samples is low (or I try without skipping these samples), the problem of the
silence samples is evident.

This is using the mp3 decoder.

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