Re: [PATCH] media: hantro: Support H264 profile control

[Tomasz Figa <tfiga@chromium.org>]

On Mon, Feb 3, 2020 at 9:00 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>
> On 2/3/20 12:13 PM, Tomasz Figa wrote:
> > On Sat, Jan 18, 2020 at 10:31 PM Nicolas Dufresne <nicolas@ndufresne.ca> wrote:
> >>
> >> Le vendredi 10 janvier 2020 à 13:31 +0100, Hans Verkuil a écrit :
> >>> On 11/29/19 1:16 AM, Tomasz Figa wrote:
> >>>> On Sat, Nov 23, 2019 at 1:52 AM Nicolas Dufresne <nicolas@ndufresne.ca>
> >>>> wrote:
> >>>>> Le samedi 23 novembre 2019 à 01:00 +0900, Tomasz Figa a écrit :
> >>>>>> On Sat, Nov 23, 2019 at 12:09 AM Nicolas Dufresne <nicolas@ndufresne.ca>
> >>>>>> wrote:
> >>>>>>> Le vendredi 22 novembre 2019 à 14:16 +0900, Hirokazu Honda a écrit :
> >>>>>>>> The Hantro G1 decoder supports H.264 profiles from Baseline to High,
> >>>>>>>> with
> >>>>>>>> the exception of the Extended profile.
> >>>>>>>>
> >>>>>>>> Expose the V4L2_CID_MPEG_VIDEO_H264_PROFILE control, so that the
> >>>>>>>> applications can query the driver for the list of supported
> >>>>>>>> profiles.
> >>>>>>>
> >>>>>>> Thanks for this patch. Do you think we could also add the LEVEL
> >>>>>>> control
> >>>>>>> so the profile/level enumeration becomes complete ?
> >>>>>>>
> >>>>>>> I'm thinking it would be nice if the v4l2 compliance test make sure
> >>>>>>> that codecs do implement these controls (both stateful and stateless),
> >>>>>>> it's essential for stack with software fallback, or multiple capable
> >>>>>>> codec hardware but with different capabilities.
> >>>>>>>
> >>>>>>
> >>>>>> Level is a difficult story, because it also specifies the number of
> >>>>>> macroblocks per second, but for decoders like this the number of
> >>>>>> macroblocks per second it can handle depends on things the driver
> >>>>>> might be not aware of - clock frequencies, DDR throughput, system
> >>>>>> load, etc.
> >>>>>>
> >>>>>> My take on this is that the decoder driver should advertise the
> >>>>>> highest resolution the decoder can handle due to hardware constraints.
> >>>>>> Performance related things depend on the integration details and
> >>>>>> should be managed elsewhere. For example Android and Chrome OS manage
> >>>>>> expected decoding performance in per-board configuration files.
> >>>>>
> >>>>> When you read datasheet, the HW is always rated to maximum level (and
> >>>>> it's a range) with the assumption of a single stream. It seems much
> >>>>> easier to expose this as-is, statically then to start doing some math
> >>>>> with data that isn't fully exposed to the user. This is about filtering
> >>>>> of multiple CODEC instances, it does not need to be rocket science,
> >>>>> specially that the amount of missing data is important (e.g. usage of
> >>>>> tiles, compression, IPP all have an impact on the final performance).
> >>>>> All we want to know in userspace is if this HW is even possibly capable
> >>>>> of LEVEL X, and if not, we'll look for another one.
> >>>>>
> >>>>
> >>>> Agreed, one could potentially define it this way, but would it be
> >>>> really useful for the userspace and the users? I guess it could enable
> >>>> slightly faster fallback to software decoding in the extreme case of
> >>>> the hardware not supporting the level at all, but I suspect that the
> >>>> majority of cases would be the hardware just being unusably slow.
> >>>>
> >>>> Also, as I mentioned before, we already return the range of supported
> >>>> resolutions, which in practice should map to the part of the level
> >>>> that may depend on hardware capabilities rather than performance, so
> >>>> exposing levels as well would add redundancy to the information
> >>>> exposed.
> >>>
> >>> There is a lot of discussion here, but it all revolves around a potential
> >>> LEVEL control.
> >>>
> >>> So I gather everyone is OK with merging this patch?
> >>
> >> I'm ok with this. For me, the level reflects the real time performance
> >> capability as define in the spec, while the width/height constraints usually
> >> represent an addressing capabicity, which may or may not operate real-time.
> >>
> >
> > I'd like to see the level control documentation improved before we
> > start adding it to the drivers. I'll be okay with that then as long as
> > the values are exposed in a consistent and well defined way. :)
> >
> > As for this patch, Hans, are you going to apply it?
>
> It's in a PR for 5.7. I had hoped it would go in for v5.6, but it was
> too late for that.

Okay, thanks!

>
> Regards,
>
>         Hans
>
> >
> > Best regards,
> > Tomasz
> >
> >>>
> >>> If not, let me know asap.
> >>>
> >>> Regards,
> >>>
> >>>       Hans
> >>>
> >>>>>>>> Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
> >>>>>>>> ---
> >>>>>>>>  drivers/staging/media/hantro/hantro_drv.c | 10 ++++++++++
> >>>>>>>>  1 file changed, 10 insertions(+)
> >>>>>>>>
> >>>>>>>> diff --git a/drivers/staging/media/hantro/hantro_drv.c
> >>>>>>>> b/drivers/staging/media/hantro/hantro_drv.c
> >>>>>>>> index 6d9d41170832..9387619235d8 100644
> >>>>>>>> --- a/drivers/staging/media/hantro/hantro_drv.c
> >>>>>>>> +++ b/drivers/staging/media/hantro/hantro_drv.c
> >>>>>>>> @@ -355,6 +355,16 @@ static const struct hantro_ctrl controls[] = {
> >>>>>>>>                       .def =
> >>>>>>>> V4L2_MPEG_VIDEO_H264_START_CODE_ANNEX_B,
> >>>>>>>>                       .max =
> >>>>>>>> V4L2_MPEG_VIDEO_H264_START_CODE_ANNEX_B,
> >>>>>>>>               },
> >>>>>>>> +     }, {
> >>>>>>>> +             .codec = HANTRO_H264_DECODER,
> >>>>>>>> +             .cfg = {
> >>>>>>>> +                     .id = V4L2_CID_MPEG_VIDEO_H264_PROFILE,
> >>>>>>>> +                     .min = V4L2_MPEG_VIDEO_H264_PROFILE_BASELINE,
> >>>>>>>> +                     .max = V4L2_MPEG_VIDEO_H264_PROFILE_HIGH,
> >>>>>>>> +                     .menu_skip_mask =
> >>>>>>>> +                     BIT(V4L2_MPEG_VIDEO_H264_PROFILE_EXTENDED),
> >>>>>>>> +                     .def = V4L2_MPEG_VIDEO_H264_PROFILE_MAIN,
> >>>>>>>> +             }
> >>>>>>>>       }, {
> >>>>>>>>       },
> >>>>>>>>  };
> >>
>