[FFmpeg-devel] parameter ranges bug / minrate q

[Michael Niedermayer]

On Fri, Jul 18, 2008 at 11:47:01AM -0700, tripp wrote:
[...]
>  @example
>  ffmpeg -i input.avi -r 24 output.avi
>  @end example
>  
> -* To force the frame rate of input file to 1 fps and the output file to 24 fps:
> +* To force the frame rate of input file (valid for raw formats only) to 1 fps and the output file to 24 fps:

This could be considered a bug, i think we even have a issue about it on
roundup ...


>  @example
> -ffmpeg -r 1 -i input.avi -r 24 output.avi
> +ffmpeg -r 1 -i input.m2v -r 24 output.avi
>  @end example
>  
>  The format option may be needed for raw input files.
> @@ -217,7 +212,7 @@
>  @code{hh:mm:ss[.xxx]} syntax is also supported.
>  
>  @item -fs @var{limit_size}
> -Set the file size limit.
> +Set the file size limit. (in bytes)
>  
>  @item -ss @var{position}
>  Seek to given time position in seconds.

ok


> @@ -388,8 +383,15 @@
>  Set video bitrate tolerance (in bit/s).
>  @item -maxrate @var{bitrate}
>  Set max video bitrate (in bit/s).
> +Requires -bufsize to be set.
>  @item -minrate @var{bitrate}
>  Set min video bitrate (in bit/s).
> +Most useful in setting up a CBR encode:
> + at example
> +ffmpeg -i myfile.avi -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v
> + at end example

ok


> +It is of little use elsewise

ok


> +and when setting a -minrate that doesn't equal -maxrate you'll get this warning:
> +Warning min_rate > 0 but min_rate != max_rate isn't recommended!
>  @item -bufsize @var{size}
>  Set video buffer verifier buffer size (in bits).
>  @item -vcodec @var{codec}

iam not sure about this, this doesnt seem too usefull ...


> @@ -435,10 +437,10 @@
>  @item -qdiff @var{q}
>  maximum difference between the quantizer scales (VBR)
>  @item -qblur @var{blur}
> -video quantizer scale blur (VBR)
> +video quantizer scale blur (VBR) (range 0.0 - 1.0)

ok


>  @item -qcomp @var{compression}
> -video quantizer scale compression (VBR)
> -
> +video quantizer scale compression (VBR) (range 0.0 - 1.0,  default 0.5)

not strictly true


> +it's not recommended to set this value at its extremes.
>  @item -lmin @var{lambda}
>  minimum video lagrange factor (VBR)
>  @item -lmax @var{lambda}

why?


> @@ -605,7 +607,10 @@
>  @item -qphist
>  Show QP histogram.
>  @item -vbsf @var{bitstream_filter}
> -Bitstream filters available are "dump_extra", "remove_extra", "noise".
> +Bitstream filters available are "dump_extra", "remove_extra", "noise", "h264_mp4toannexb".

ok


> + at example
> +ffmpeg -i h264.mp4 -vcodec copy -vbsf h264_mp4toannexb -an out.h264
> + at end example
>  @end table

ok


[and yes you will have to split the seperate things unless diego or another
is in very good mood and does it ...]


>  
>  @section Audio Options

> Index: libavcodec/avcodec.h
> ===================================================================
> --- libavcodec/avcodec.h	(revision 14281)
> +++ libavcodec/avcodec.h	(working copy)
> @@ -990,6 +990,8 @@
>  
>      /**
>       * qscale factor between IP and B-frames
> +     * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
> +     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
>       * - encoding: Set by user.
>       * - decoding: unused
>       */
> @@ -1128,8 +1130,6 @@
>  
>      /**
>       * qscale offset between IP and B-frames
> -     * If > 0 then the last P-frame quantizer will be used (q= lastp_q*factor+offset).
> -     * If < 0 then normal ratecontrol will be done (q= -normal_q*factor+offset).
>       * - encoding: Set by user.
>       * - decoding: unused
>       */

ok

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

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
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