[Libav-user] calc next audio pts value

[Nicolas Sugino]

2013/8/5 Patrick Fischer <pfischer at como.com>

> **
>
> Hello
>
>
>
> I would like to understand how i can calc the diff to the next PTS Value.
>
> Im processing a dvb stream. To be in sync i detect if a frame is missing
> and add a dummy frame.
>
> For video frames a can use this formula:
>
>
>
>  (1/fps) * 90000 * NUMBER_OF_THE_FRAME
>
> example:
>
> (1 / 30) * 90000 * 1 = 3600
>
>
>
> i can't find out the formula for audio pts values.
>
> if i print out the diff to the last audio pts it is
>
>     Stream #0:2[0x66](deu): Audio: mp2 ([3][0][0][0] / 0x0003), 48000 Hz,
> stereo, s16p, 256 kb/s
>
> diff to last pts 2880
>
>
>
> If i take an other video:
>
>     Stream #0:1[0x1412](deu): Audio: mp2 ([3][0][0][0] / 0x0003), 48000
> Hz, stereo, s16p, 192 kb/s
>
> diff to last pts 2160
>
>
>
> Can anybody give me a hint?
>
>
>
> Best Regards
>
> Patrick
>
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>
>
Hi

I've been using the following:

being:
AVCodecContext *cc;
AVStream *st;

then:
(cc->frame_size / cc->sample_rate) * (st->time_base.den /
st->time_base.num) * number

I first multiply everything and then do the divisions for rounding reasons.

Also, that 90000 you put in the first formula would be the stream
(time_base.den / stream time_base.num), it may not be always 90000.

I don't know if this is the right way, but this way seemed to work for me.
If someone knows better please add further info or correct this

Regards
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