[FFmpeg-user] Image Conversion TIFF > JPEG with yuv422 chroma subsampling

Moritz Barsnick barsnick at gmx.net
Wed Jan 21 10:16:18 CET 2015

On Wed, Jan 21, 2015 at 09:33:21 +0100, Andrea Rastelli wrote:
> Actually the problem is not in the creation of the JPEG itself, but in 
> the resulting chroma subsampling that (apparently) is not stored in the 
> FFmpeg resulting image.

You did not mention this so far within this thread, if I may point this

> With ImageMagick, when I set -sampling-factor 4:4:4 or 4:2:2 a tool like 
> "mediainfo" shows the exact subsampling. With ffmpeg this information is 
> not set nor visible.

Unfortunately, I don't know much about this topic.

> Also, ImageMagick produce a bigger file (1.4Mb) than ffmpeg (0.1Mb).
> If, with FFMpeg, exists some parameter that produce the same result that 
> I have obtained with ImageMagick will be prefect (because, now, I have 
> two different tools to manage in my scripts)

I can't manage to tickle extremely high quality out of ffmpeg, but the
resulting image with -q:v 0..2 is very good. I converted a big JPEG,
and the resulting file never reached more than half the size of the
original, despite it being a recoding. Either my original had too much
redundancy, or ffmpeg wasn't investing enough. ;-)

But I think my method and my argumentation are totally wrong. Yet
either way, the resulting image can't be considered bad.

You may want to give us samples - an input TIFF, your ffmpeg results,
and your ImageMagick results.


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