On 06/07/18 12:32, Philipp Zabel wrote: > On Thu, 2018-06-07 at 09:27 +0200, Hans Verkuil wrote: > [...] >>>>>> I think it could be useful to enforce the same colorimetry on CAPTURE >>>>>> and OUTPUT queue if the hardware doesn't do any colorspace conversion. >>>>> >>>>> After thinking a bit more on this, I guess it wouldn't overly >>>>> complicate things if we require that the values from OUTPUT queue are >>>>> copied to CAPTURE queue, if the stream doesn't include such >>>>> information or the hardware just can't parse them. >>>> >>>> And for encoders it would be copied from CAPTURE queue to OUTPUT queue? >>>> >>> >>> I guess iy would be from OUTPUT to CAPTURE for encoders as well, since >>> the colorimetry of OUTPUT is ultimately defined by the raw frames that >>> userspace is going to be feeding to the encoder. >> >> Correct. All mem2mem drivers should just copy the colorimetry from the >> output buffers to the capture buffers, unless the decoder hardware is able to >> extract that data from the stream, in which case it can overwrite it for >> the capture buffer. >> >> Currently colorspace converters are not supported since the V4L2 API does >> not provide a way to let userspace define colorimetry for the capture queue. > > Oh, I never realized this limitation [1] ... > > "Image colorspace, from enum v4l2_colorspace. This information > supplements the pixelformat and must be set by the driver for capture > streams and by the application for output streams, see Colorspaces." > > [1] https://linuxtv.org/downloads/v4l-dvb-apis-new/uapi/v4l/pixfmt-v4l2.html > > It's just a bit unintuitive that the initialization sequence requires to > set S_FMT(CAP) first and then S_FMT(OUT) but with colorspace there is > information that flows the opposite way. > >> I have a patch to add a new v4l2_format flag for that since forever, but >> since we do not have any drivers that can do this in the kernel it has never >> been upstreamed. > > Has this patch been posted some time? I think we could add a mem2mem > device to imx-media with support for linear transformations. I don't believe it's ever been posted. It's here: https://git.linuxtv.org/hverkuil/media_tree.git/commit/?h=csc&id=d0e588c1a36604538e16f24cad3444c84f5da73e Regards, Hans
