[FFmpeg-devel] Fix ffmpeg -re behaviour

Luca Abeni lucabe72
Sun Nov 23 17:40:20 CET 2008

Michael Niedermayer wrote:
>> * fixrate-emu-pts.patch
>>   Use ist->next_pts rather than use frame_nb * codec_time_base as the
>>   timestamp for the next frame to print.
>>   This assumption is not always true and only works for video codecs anyway.
> I dont think next_pts is the correct variable to use, but then what exactly
> where the use cases of rate_emu anyway?

rate_emu should read a stream and transcode it at a rate given by the 
input timestamps. I find it useful when streaming, or when doing 
real-time video conversion without consuming too much CPU time.

In theroy, I think that the input dts should be used, but it can often 
be AV_NOPTS_VALUE... I see that ffmpeg.c sets next_pts according to the 
input dts, and then updates it (with the guessed value) so that it will 
have a reasonable value even if the next dts is AV_NOPTS_VALUE.
So, I had the impression that next_pts can be used in this case (the 
exact value is not really important; the important thing is to maintain 
an acceptable average rate).

Would ist->pts be a better solution?


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