[FFmpeg-user] How to lossless crop mp4 videos

[Ulf Zibis]

Am 16.08.21 um 09:44 schrieb Nicolas George:
> Ulf Zibis (12021-08-16):
>> if I understand correct, mp4 videos are encoded in blocks of 16x16
>> pixels. I I'm wondering if I could crop a video by multiples of 16
>> pixels without reencoding the remaining blocks.
> It depends on the codec, not the format.
>
> With a codec like MJPEG, it is possible. There are tools to do it with
> individual images, look up jpegtran.
>
> But with video codecs that use temporal compression, a visible part of
> the next image can depend on a cropped part of the current image, and
> that makes it impossible.

Thanks Nicolas!

Your explanation makes sense to me.

-Ulf