[FFmpeg-devel] [PATCH 1/2] docs/filters: add documentation to all existing OpenCL filters

[Gyan Doshi]

On 03-08-2018 08:46 PM, Danil Iashchenko wrote:

> +For most general-purpose filters, no conversion is required.
> +
> +In case a file contains an alpha channel supported by the format, then explicit conversion is a requirement.

This is unclear. So, if the input's pixel format has alpha, we should 
convert? to what? In the example below, the conversion target also has 
alpha. Does RGB24 need to be converted?

> + at item
> +Insert a PNG logo in the top-left corner of the INPUT. Explicit format conversion is a must.
> + at example
> +-i INPUT -i LOGO -filter_complex "[0:v]hwupload[a], [1:v]format=yuva420p, hwupload[b], [a][b]overlay_opencl, hwdownload" OUTPUT

PNGs, afaik, are always full chroma. Shouldn't we convert to yuva444p?

Regards,
Gyan