Le jeudi 27 juin 2024 à 16:13 +0800, Jianfeng Liu a écrit : > Hi Nicolas, > > On Wed, 26 Jun 2024 13:46:03 -0400, Nicolas Dufresne wrote: > > Just to clarify, since you are right that it won't work well with GStreamer. It > > does work with multiple decoders (it exposes them all), it is simply that it > > will randomly pick one when decoding, and it may not pick the best one. > > I have tested rkvdec2 and vpu121 with gstreamer 1.24.2 on rk356x to decode > a 4K video, and gstreamer always fall with error: > "v4l2slh264dec0: Failed to configure H264 decoder". > I guess that's because 1080p vpu is at fdea0000 which is always > initialized earlier than rkvdec2 at fdf80200, so gstreamer will always > choose the 1080p decoder. I've never done any research, but that is plausible. - Probe happen in address order, since DT are in address order - Media notes are assigned in probe order - GStreamer register the element in the same order in its registry - In adsence of a rank or capabilities to differentiate, the probe order is maintained. > > > In the long term, I'd like to stop having to do "like downstream" and expose > > them all. I believe the fix is fairly straightforward in GStreamer. We need to > > expose in the generated element the width/height ranges, and for H.264 the > > supported profiles and level. With that, we at least won't randomly fail at > > decoding 4K, and it should be good enough. > > Not only gstreamer, chromium also has similar issue. Chromium will only > check video resolution globally before starting to use one decoder: if > there is a 4K decoder detected before, it will mark 4K resolution as > supported. But when decoding videos, it will choose the first decoder > supporting profile like H264. So chromium may use a 1080p decoder to > decode a 4K video. > > Chromium's code about v4l2 is complicated for me. I may create a bug about > it. But chrome os doesn't support devices with multi v4l2 decoders like > rockchip's socs, I don't know if they have the motion to fix it quickly. That's an interesting bug, which makes its more of less equal to GStreamer "unimplemented behaviour". Filing a bug is best indeed, ChromeOS team, who maintains this, is probably unaware as they don't have any SoC with multiple decoders. Even on PC side, their Chromebooks only ever have a single GPU, I haven't heard about any eGPU support either. > > > For RK3588, which is a new SoC, its not a problem to upstream something that > > does not work with existing userspace. It would only be a regression if we where > > to enable VDPU121 on RK3399, as now updating linux would cause bugs with > > existing userspace. > > There is an old soc just like RK3399: RK3328, which also has a 1080p > hantro h264 decoder and a 4K rkvdec h264 decoder. I guess less people care > about its mainline decoding with gstreamer/chromium so it still has 1080p > decoder enabled. What I meant by new/old, is supported mainline or not. But yes, on timeline, there is many older SoC with dual decoders in the Rockchip line. > > > For users, it would be best if we get this sorted out in GStreamer by the time > > we have a second decoder. Note that I have some vacation coming up this month, > > so there might be extra delays. Yet, its logical to merge this (the "worst" > > decoder) first, since then randomly picking a better one won't be a regression. > > Happy vacation days! I will also take a look at chromium's code to see if > I can fix it. Great, let's keep everyone on sync, I'm sure we can come up with something better then disabling the possibly useful hardware. Nicolas
