On Tue, Sep 20, 2011 at 4:20 AM, j-b-m <[email protected]> wrote:
> Hi.
>
> Following Kdenlive bug 2318 ( http://kdenlive.org/mantis/view.php?id=2318 ),
> I discovered a bug in FFmpeg's argument handling, bug report is here:
>
> https://ffmpeg.org/trac/ffmpeg/ticket/491
>
> The bug was acknowledged, but the answer from an FFmpeg's developer is that
> we should use the "vb" option instead of the "b" option to set the video
> bitrate (that is compatible with previous versions).
>
> However, in my tests, the "vb" option works in FFmpeg, but not in MLT:
>
> ffmpeg -i 00006.MTS -acodec mp2 -vcodec mpeg2video -vb 12000k test.mpg
>
> gives a high bitrate output clip.
>
> melt 00006.MTS -consumer avformat:test2.mpg acodec=mp2 vcodec=mpeg2video
> vb=12000k
>
> gives a default low bitrate output clip.
>
> Dan, do you have an idea if this is easily fixable? Probably related to
> AVOption...
>

ffmpeg the utility strips off the first character if it is a, v or s
and the remainder matches an option name. MLT does not do that, and I
am not sure I want to do that. I prefer to report and use the option
names straight-up and not do this prefixing and stripping dance. Then,
a recent change in libav* is that a single option can apply to
multiple codecs and formats. I am not sure where all of this is going.
At the end of the day, there is no (and never was) "vb" AVOption -
only "b". There used to be a discrete "ab" AVOption. Is that gone now
effectively making the API users adopt the 'a' and 'v' prefix dance? I
will have to look into this and compare it to what libav is doing.

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