Re: [PATCH] media: docs: dev-decoder: Trigger dynamic source change for colorspace

[Nicolas Dufresne]

Hi,

Le mardi 07 janvier 2025 à 14:36 +0900, Ming Qian a écrit :
> If colorspace changes, the client needs to renegotiate the pipeline,
> otherwise the decoded frame may not be displayed correctly.
> 
> If it can trigger an source change event, then client can switch to the
> correct stream setting. And each frame can be displayed properly.
> 
> So add colorspace as a trigger parameter for dynamic resolution change.
> 
> Signed-off-by: Ming Qian <ming.qian@xxxxxxxxxxx>
> ---
>  Documentation/userspace-api/media/v4l/dev-decoder.rst | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/dev-decoder.rst b/Documentation/userspace-api/media/v4l/dev-decoder.rst
> index ef8e8cf31f90..49566569ad26 100644
> --- a/Documentation/userspace-api/media/v4l/dev-decoder.rst
> +++ b/Documentation/userspace-api/media/v4l/dev-decoder.rst
> @@ -932,7 +932,9 @@ reflected by corresponding queries):
>  
>  * the minimum number of buffers needed for decoding,
>  
> -* bit-depth of the bitstream has been changed.
> +* bit-depth of the bitstream has been changed,
> +
> +* colorspace of the bitstream has been changed.

Did you really mean colorspace in the way this term is used in V4L2 ? What we
want this event to be used for is when the capture storage size or amount
changes, perhaps you mean when the capture pixelformat changes ? This will
indeed happen if you change the bit-depth, subsampling (not mentioned here
either) or change the way colors are repsented (RGB, YCbCr, etc.).

>  
>  Whenever that happens, the decoder must proceed as follows:
>