[Libav-user] Adjust fps

Leandro Raffo ljraffo at gmail.com
Thu Sep 8 19:10:48 EEST 2016

2016-09-07 14:59 GMT-03:00 Henry, David <David.Henry at echostar.com>:
> On 9/6/16, 11:23 AM, "Libav-user on behalf of Leandro Raffo"
> <libav-user-bounces at ffmpeg.org on behalf of ljraffo at gmail.com> wrote:
>>I'm trying to remux a video changing its frame rate, but I'm a bit
>>lost in how to do it. This is what I have in mind:
>>Suppose I have a 20 fps video and I want to take it for example to 10
>>fps, should I drop every second frame (paket) and JUST multiply the
>>dts and pts by 2.
>>What if I want to go 3 or 7 or 13 fps? I'm guessing I should be
>>rescaling the dts and pts using the input_stream time_base or
>>avg_frame_rate to get something reliable, but I don't know how!
> To change the frame rate, you must first decode the video frames as you
> receive them.  Don¹t throw away
> The AVPacket before decoding to an AVFrame.  After decoding, you can throw
> away every other frame
> Or whatever you decide based on your frame rate.  You don¹t need the dts
> after decoding.  Don¹t
> Change the pts because it¹s the presentation timestamp and you want to
> display the frame in the
> Same place in the timeline, only fewer frames.
> David Henry
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I see, but I wanted to avoid doing a decode/encode stage. Guess its
not possible then.

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