Re: [PATCH RFC 0/7] media: qcom: iris: add support for decoding 10bit formats

[Dmitry Baryshkov]

On Wed, Apr 08, 2026 at 09:04:02PM -0400, Nicolas Dufresne wrote:
> Hi,
> 
> Le jeudi 09 avril 2026 à 03:02 +0300, Dmitry Baryshkov a écrit :
> > On Wed, Apr 08, 2026 at 06:43:53PM +0200, Neil Armstrong wrote:
> > > This adds the plumbing to support decoding HEVC and AV1
> > > streams into 10bit pixel formats, linear and compressed.
> > > 
> > > This has only been tested on SM8650 with HEVC, and was inspired by
> > > Venus and the downstream vidc driver for the buffer
> > > calculations and HFI messages.
> > > 
> > > I was unable to get 10bit decoding working with Gstreamer
> > > and ffmpeg, but v4l2-ctl works with:
> > 
> > Any particular errors? I assume Gstreamer needs to be taught about
> > Q10C. But P010 should (hopefully) work.
> 
> P010 should work for both Gst and FFMPEG, its probably a user error, or there is
> a hidden bug in the driver that make it fail, v4l2-ctl is very permissive as it
> simply dump to disk. You should provide an updated fluster score, so you have to
> use one of these.
> 
> For Q10C on GStreamer, it needs mapping [0] and you need some bugfix [1] and
> another that I will be sending tomorrow. We had never tested video compression
> with this module before.
> 
> [0] https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8195
> [1] https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/11222
> 
> The last issue has to do with:
> https://gitlab.freedesktop.org/gstreamer/gstreamer/-/blob/38965e2d9c1119674a65dc437ee7e8ec95339f31/subprojects/gst-plugins-good/sys/v4l2/gstv4l2object.c#L4378
> 
> V4L2 format gives us the number of allocation, but not really the number of
> planes, and we forgot to initialize that number for the "opaque" format case. A
> tempory fix might be to add this after S_FMT:
> 
> if (GST_VIDEO_INFO_FORMAT (&info.vinfo) == GST_VIDEO_FORMAT_DMA_DRM)
>   n_v4l_planes = format.fmt.pix_mp.num_planes;
> 
> Works for AFBC and QC at leat, since both are unambiguously single plane, and so
> cannot have mplane variants.

Reading this made me realize another suggestion for Neil:

Please check that the data returned by Iris matches the display driver
expectations. See the comments in the _dpu_format_populate_addrs_ubwc().

> 
> Let me know how far you get! Please be aware that Robert and I are making these
> patches based on feedback, we don't have access to any boards capable of
> decoding to QC compressed formats.
> 
> > 
> > > v4l2-ctl --verbose --set-fmt-video-out=pixelformat=HEVC --set-fmt-video=pixelformat=P010 --stream-mmap --stream-out-mmap --stream-from-hdr Big_Buck_Bunny_1080_10s_30MB_main10.h265.hdr --stream-to out.P010
> > > v4l2-ctl --verbose --set-fmt-video-out=pixelformat=HEVC --set-fmt-video=pixelformat=Q10C --stream-mmap --stream-out-mmap --stream-from-hdr Big_Buck_Bunny_1080_10s_30MB_main10.h265.hdr --stream-to out.QC10
> > > 
> > > The non-10bit decoding still works as before.
> > > 
> > > With Big_Buck_Bunny_1080_10s_30MB reencoded in 10-bit profile
> > > and tranformed in v4l2 header format with [1]:
> > > ffmpeg -i Big_Buck_Bunny_1080_10s_30MB.h264 -pix_fmt yuv420p10le -c:v libx265 -crf 28 -x265-params profile=main10 Big_Buck_Bunny_1080_10s_30MB_main10.h265
> > > /path/to/mkhdr.sh Big_Buck_Bunny_1080_10s_30MB_main10.h265 raw Big_Buck_Bunny_1080_10s_30MB_main10.h265.hdr
> > > 
> > > The frames correctness has been verified buy displaying them
> > > via Vulkan DMA_BUF import, including QC10C and QC08C.
> 
> In GStreamer, once the video4linux plugin issues are fixed, you should be able
> to display the frames using glimagesink. GL only allow for RGB render, which
> damages the data, so its not good enough for conformance testing with
> compression enabled, but usually just doing visual inspection is acceptable.

Nice! Looking forward to testing Q08C aka NV12-UBWC on the display.
Maybe I should try rebuilding the plugins with the mentioned patches and
provide my r-b or report issues there.


-- 
With best wishes
Dmitry