[Libav-user] Using libavformat/libavcodec with sample accurate seeking

[Christopher Snowhill]

On 8/28/16 9:56 AM, salsaman wrote:
>
>
> On Sun, Aug 28, 2016 at 1:55 PM, Christopher Snowhill
> <kode54 at gmail.com <mailto:kode54 at gmail.com>> wrote:
>
>
>
>     On 8/28/16 12:50 AM, Paul B Mahol wrote:
>>     Hi,
>>
>>     On Sun, Aug 28, 2016 at 7:16 AM, Christopher Snowhill
>>     <kode54 at gmail.com <mailto:kode54 at gmail.com>> wrote:
>>
>>         I've noticed that when using these libraries in my own
>>         projects, at
>>         least in VGMStream, and with the WMA Pro codec, it is
>>         necessary to
>>         perform my own pre-roll when seeking for looping, or else the
>>         codec
>>         ramps the audio in from silence on every loop as it catches
>>         back up to a
>>         valid state. I currently use either two seconds, or the
>>         beginning of the
>>         file if it's less than two seconds prior to the intended seek
>>         point,
>>         then discard sample data that is returned by the decoder.
>>
>>         Is this always necessary by design? Or am I misusing the
>>         seeking API?
>>
>>         I currently use:
>>
>>         int64_t ts = target_sample * formatCtx->duration / total_samples;
>>         avformat_seek_file(formatCtx, -1, ts - 1000, ts, ts,
>>         AVSEEK_FLAG_ANY);
>>
>>
>>     Do you call avcodec_flush_buffers()?
>     Yes, I do. Immediately after avformat_seek_file.
>>
>>
>>
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>
> Does it make a difference if you use AV_SEEK_FLAG_BACKWARDS ? 
No.
> http://lives-video.com https://www.openhub.net/accounts/salsaman
>
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