Well, basically, many avfilters are simply incompatible, and we blacklist
some, but we have not taken the time to audit all of them, and they are
adding many all the time. In this case, the error occurs because the output
width and height do not match the width and height that MLT needs - as
expected for a crop. In MLT, at some point, all video frames need to
conform in order to allow mixing or to give the output consumer what it
requested in a consistent manner. For that MLT automatically adds
normalization filters to deinterlace, change field order, scale, pad,
resample audio, correct # audio channels, etc. MLT's native crop filter is
special because it has two pars: one that is first in normalization and one
the user adds that directs the first one. This allows the scaling and
padding filters to apply to the output of the first part. In short,
avfilter.crop cannot work in MLT, and you should use the MLT crop filter.
In the context of all of this, crop has an interesting behavior that you
can observe in shotcut or similar. You first need to figure out what
resolution and aspect ratio you want as a result, use that as a MLT
profile, and then crop. You cannot simply say take this input crop X from
top and bottom, compute the result for me, and give it to me.
On Mon, Oct 10, 2016 at 11:09 PM Geoffroy Montel <
[email protected]> wrote:
> Dear list,
>
> I've been trying to use avfilter crop filter, but I'm getting some errors.
>
> melt crop.jpg in=0 out=100 -attach avfilter.crop av.x=0 av.y=0
> av.out_w=300 av.out_h=300 -progress -consumer avformat:crop.mp4
>
> returns
>
> [filter avfilter.crop] Unexpected return format
>
> and the image is not cropped.
>
> Am I doing something wrong ?
>
> Thanks in advance for your help, all the best
>
> geoffroy
>
>
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