[FFmpeg-user] Changing DAR ?

[Paul B Mahol]

On 10/8/13, Ronald F. Guilmette <rfg at tristatelogic.com> wrote:
>
> In message <loom.20131008T121902-356 at post.gmane.org>,
> Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
>
>>Ronald F. Guilmette <rfg <at> tristatelogic.com> writes:
>>
>>> I am trying to use ffmpeg (2.0.1) to make what I believe
>>> should be a simple change in a video file I have, and
>>> it's just not happening, so I need to ask what I am
>>> doing wrong.
>>
>>Please post your command line together with the complete,
>>uncut console output.
>
>
> Thank you.  I would, but it might be embarassing. (1/2 :-)
>
> But seriously, I've (now, finally) managed to get done what I wanted to
> get done, as far as manipulating the aspect ratio(s) in the actual video
> file, but as I described at some length in my immediately prior posting,
> the documentation of this stuff could use some improvement.
>
> As I mentioned, earlier I had tried this, which did not seem to have
> any effect at all:
>
>     ffmpeg -i foo.avi -acodec copy -vcodec copy -vf setdar=16:9 bar.avi
>
> Now I have tried instead:
>
>     ffmpeg -i foo.avi -acodec copy -vcodec copy -vf setdar=16/9 bar.avi
>
> the subtle difference being the use of a '/' instead of a colon when
> specifying the desired DAR.  Anyway, that seemed to work, although
> going by the examples here:
>
>      http://ffmpeg.org/ffmpeg-filters.html#Examples-19
>
> it should not have, because I neglected to insert also a "dar=" or
> "ratio=" sub-sub-clause.
>
> I understand now that within the arguments given in/for the setdar and
> setsar sub-options, when it is desired to express a ratio, that ratio
> must be written in the form:
>
> 	numerator/denominator
>
> and now that I've looked at the examples located at the URL just above
> I can even understand why this is necessary (i.e. because colons are
> used as sub-sub-option delimiters/separators, so they can't be used within
> the actual arguments given for the sub-sub-options) but still, I could
> have sworn that I had seen some examples somewhere which showed ratios
> of the form:
>
> 	numerator:denominator
>
> being used or specified within some different ffmpeg options (or
> sub-options).
> If so, then I'd like to just re-assert that it is quite confusing to the
> end-luser (like me) to have to write ratios in different formats, depending
> in the specific context within the ffmpeg command line one is dealing with.

The documentation clearly states that in that case ':' should be escaped.

>
>
> Regards,
> rfg
>
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