[FFmpeg-user] Chroma subsampling formats

[Paul B Mahol]

On Tue, Jul 15, 2025 at 6:00 PM Mark Filipak <markfilipak.imdb at gmail.com>
wrote:

> Are these correct? Or, is there some official reference I can consult?
>

Maybe correct for packed formats only.


> --Mark.
>
> KEY:
> ¤ —— Element exists in the field and is sampled
> • —— Element exists in the field but is not sampled
>    —— (blank) Element doesn't exist in the field
>
> Reference: https://en.wikipedia.org/wiki/Chroma_subsampling


Isn't this very obvious and straightforward read?

Also you forgot that chroma, when subsampled, can have different positions,
top, top-left, center, ..



>
>
>             Y element, pixels 0..3
>            /    Cb element, pixels 0..3
>           /    /    Cr element, pixels 0..3
>          /    /    /
> 4:4:4  ¤¤¤¤ ¤¤¤¤ ¤¤¤¤ —— lines in field 0
>         ¤¤¤¤ ¤¤¤¤ ¤¤¤¤ —— lines in field 1
>
> 4:4:2  ¤¤¤¤ ¤¤¤¤ ¤¤¤¤
>         ¤¤¤¤ ¤•¤• ¤•¤•
>
> 4:4:2  ¤¤¤¤ ¤¤¤¤ ¤¤¤¤  // JPEG variant according to the reference
>         ¤¤¤¤      ¤¤¤¤
>
> 4:4:1  ¤¤¤¤ ¤¤¤¤ ¤¤¤¤
>         ¤¤¤¤ ¤••• ¤•••
>
> 4:4:0  ¤¤¤¤ ¤¤¤¤ ¤¤¤¤
>         ¤¤¤¤
>
> 4:2:2  ¤¤¤¤ ¤•¤• ¤•¤•
>         ¤¤¤¤ ¤•¤• ¤•¤•
>
> 4:2:1  ¤¤¤¤ ¤•¤• ¤•¤•
>         ¤¤¤¤ ¤••• ¤•••
>
> 4:2:1  ¤¤¤¤ ¤•¤• ¤•¤•  // JPEG variant according to the reference
>         ¤¤¤¤      ¤•••
>
> 4:2:0  ¤¤¤¤ ¤•¤• ¤•¤•
>         ¤¤¤¤
>
> 4:1:1  ¤¤¤¤ ¤••• ¤•••
>         ¤¤¤¤ ¤••• ¤•••
>
> 4:1:0  ¤¤¤¤ ¤••• ¤•••
>         ¤¤¤¤
>
> 4:0:0  ¤¤¤¤            // My conjecture
>         ¤¤¤¤
>
> 3:1:1  ¤¤¤  ¤••  ¤••   // Sony variant according to the reference
>         ¤¤¤  ¤••  ¤••
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