Theora encode bitrate bug.

[igor]

In ./libavcodec/libtheoraenc.c:

t_info.target_bitrate = avc_context->bit_rate;

It's wrong!

Right way is:
From ffmpeg2theora (​http://svn.xiph.org/trunk/ffmpeg2theora/src/ffmpeg2theora.c)

/*Account for the Ogg page overhead.
              This is 1 byte per 255 for lacing values, plus 26 bytes per 4096 bytes for
               the page header, plus approximately 1/2 byte per packet (not accounted for
               here).
         */
t_info.target_bitrate = (int) (64870 * (ogg_int64_t)avc_context->bit_rate >> 16);

Attach small path

[Carl Eugen Hoyos]

FFmpeg allows to mux theora into other containers (avi, mkv, nut): Isn't the patch wrong assuming only ogg?

[igor]

This parameter is used only for bitrate in theora coder. It doesn't affect the container. In other words, we specify the quality of a coded frame we would like to get from encoder.

[Carl Eugen Hoyos]

So you are saying the overhead applies even if not muxing into ogg?
Doesn't that mean the comment in the ffmpeg2theora source is wrong?

[Michael Niedermayer]

the matrix lobby scene with 1000kbps without patch: bitrate=1001.6kbits/s
the matrix lobby scene with 1000kbps with patch: bitrate= 991.8kbits/s
Thus i cannot reproduce this bug