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

[salsaman]

On Sun, Aug 28, 2016 at 1:55 PM, Christopher Snowhill <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>
> 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 ?



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