[FFmpeg-devel] [PATCH] Issue 543, clarification of -bt in docs

[Jason Garrett-Glaser]

On Sun, Jul 20, 2008 at 8:58 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sun, Jul 20, 2008 at 06:18:46PM -0700, tripp wrote:
>> patch attached
>>
>>
>> tripp
>>
>>
>>
>> Index: doc/ffmpeg-doc.texi
>> ===================================================================
>> --- doc/ffmpeg-doc.texi       (revision 14318)
>> +++ doc/ffmpeg-doc.texi       (working copy)
>> @@ -385,7 +385,10 @@
>>  @item -vn
>>  Disable video recording.
>>  @item -bt @var{tolerance}
>> -Set video bitrate tolerance (in bit/s).
>> +Set video bitrate tolerance (in bits, default 4000k).
>> +Has a minimum value of: (target_bitrate/target_framerate).
>
>> +For 1 pass BT specifies how hard the RC code should try to achieve CBR.
>
> I do not like the way this is said, because its not true and will misslead
> users into thinking low bt would achive CBR.

Better description, if a bit long:

"In 1-pass mode, bitrate tolerance specifies how far ratecontrol is
willing to deviate from the target average bitrate value.  This has
nothing to do with minimum and maximum bitrate, but rather how close
ratecontrol gets to the target bitrate.  Lower tolerance results in
worse quality."

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