[Ffmpeg-devel] [PATCH] Clarify definition of r_frame_rate

[Michael Niedermayer]

Hi

On Sat, Nov 11, 2006 at 04:02:22PM -0700, Fred Rothganger wrote:
> Greetings,
> 
> I am trying to fix some issues with the calculation of r_frame_rate in 
> av_find_stream_info().  As a first step toward that, it would be helpful 
> to clarify what r_frame_rate should be.  Attached is a patch that adds a 
> rather wordy comment to AVStream.r_frame_rate.  It describes the 
> semantics I have relied on for quite a while for seeking in mpeg files.  
> (BTW, "~24fps" means "24000/1001 fps", but it didn't seem important to 
> express that much detail.)
> 
> -- Fred

> Index: avformat.h
> ===================================================================
> --- avformat.h	(revision 6967)
> +++ avformat.h	(working copy)
> @@ -235,9 +235,19 @@
>      int id;       /* format specific stream id */
>      AVCodecContext *codec; /* codec context */
>      /**
> -     * real base frame rate of the stream.
> -     * for example if the timebase is 1/90000 and all frames have either
> -     * approximately 3600 or 1800 timer ticks then r_frame_rate will be 50/1
> +     * The "real" number of frames per second in the stream, as opposed to
> +     * the "coded" rate claimed by its metadata.  The real and coded frame
> +     * rates can differ under at least the following circumstances:
> +     * <ul>
> +     * <li>The frame rate is variable, in which case this value gives the
> +     * average number of frames per second, and the coded frame rate indicates
> +     * the time quantum.

this description is wrong, r_frame_rate is NOT the average framerate if it
where it would be called average_framerate
patch rejected

you can add a average_framerate field if you lik but you cannot change the
meaning of a different variable to match what you would want it to mean

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

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