[Ffmpeg-devel] [PATCH] fix frame duration computation in find_stream_infos

Michael Niedermayer michaelni
Sat Mar 31 21:27:09 CEST 2007


Hi

On Sat, Mar 31, 2007 at 07:44:36AM -0600, Fred Rothganger wrote:
> Michael Niedermayer wrote:
> >NO r_frame_rate is not the average framerate
> >  
> 
> We need something like "useful_frame_rate" that matches our intuitive 
> notions of the true speed of the file.  :)

no we dont, you want something you cant describe and cant implement
and you reappear every few month and complain about it


> 
> In particular, I need a value that allows me to calculate a timestamp 
> based on a frame number in a fixed rate video.  Unfortunately, it seems 
                               ^^^^^^^^^^
> that the fixed rate videos in my possesion, and apparently in the 
> possession of others as well, don't have clean enough timestamps to 
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> produce a usable r_frame_rate.

fixed rate video has per definition clean timestamps if not its not fixed
rate
also average fps will not make any more sense than r_frame_rate for such
videos



> 
> You've explained in a previous thread that the job of r_frame_rate is to 
> give the (inverse of the) smallest time quantum that all the timestamps 
> in the file fall on.  In a mixed frame rate file this will be something 
> like the LCM of the framerates.  In that thread you agreed to the idea 
> of adding an "avg_frame_rate", but I still haven't gotten around to it.  :)

so you complain about your own lazyness?


> 
> A coworker of mine described a variable rate video he generated in which 
> some frames last over a minute and others less than a second.  This is 
> probably an extreme case, 

not really, if the image doesnt change theres no sense in sending out another
frame


> but it is an existence proof that average 
> frame rate can be made useless.

it IS useless beyond providing some statistics about the video ...

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle
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