Hi Marek,
On Fri, Jan 13, 2023 at 02:03:33AM +0100, Marek Vasut wrote:
> On 1/13/23 00:15, Laurent Pinchart wrote:
> > On Tue, Jan 10, 2023 at 08:53:31PM +0100, Marek Vasut wrote:
> >> The Cypress EZUSB FX3 UVC example can be configured to report pixel
> >> format "e436eb7e-524f-11ce-9f53-0020af0ba770". This is its GUID for
> >> BGRA/X 8:8:8:8.
> >>
> >> The UVC 1.5 spec [1] only defines GUIDs for YUY2, NV12, M420 and I420.
> >> This seems to be an extension documented in the Microsoft Windows Media
> >> Format SDK[2]. This Media Format SDK defines this GUID as corresponding
> >> to `MEDIASUBTYPE_RGB32`.
> >>
> >> Note that in my case, the FX3 UVC can output either channel order,
> >> BGR or RGB or any other mix for that matter. Since Linux commit
> >> 1b8dc32286a1a ("[media] uvcvideo: Add GUID for BGR 8:8:8")
> >> defined a GUID for `MEDIASUBTYPE_RGB24` channel order as BGR, keep
> >> this change consistent and define `MEDIASUBTYPE_RGB32` as BGR as well.
> >
> > I'd like to see documentation of the MEDIASUBTYPE_RGB32 format that
> > indicates the components order precisely. While there's a high chance it
> > maps to a BGR (in the V4L2 nomenclature) format, there would still be
> > two different options for the A or X component.
>
> Maybe this ?
>
> https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/DirectShow/uncompressed-rgb-video-subtypes.md
>
> "
> Remarks
> ...
> For RGB 32, every pixel is an RGBQUAD. Each color is one byte, with a
> value from 0 to 255, inclusive. The memory layout is:
> Byte 0 1 2 3
> Value Blue Green Red Alpha or Don't Care
> "
>
> Maps to
>
> drivers/media/v4l2-core/v4l2-ioctl.c: case V4L2_PIX_FMT_BGR32:
> descr = "32-bit BGRA/X 8-8-8-8"; break;
Thank you for digging it up. Looks good to me, except that
V4L2_PIX_FMT_BGR32 is deprecated (see
https://linuxtv.org/downloads/v4l-dvb-apis/userspace-api/v4l/pixfmt-rgb.html#deprecated-rgb-formats).
You should use V4L2_PIX_FMT_BGRA32 or V4L2_PIX_FMT_BGRX32 instead.
--
Regards,
Laurent Pinchart
