Re: Hantro H1 Encoding Upstreaming

[Michael Tretter <m.tretter@pengutronix.de>]

Hi Nicolas,

On Tue, 14 Jan 2025 11:16:47 -0500, Nicolas Dufresne wrote:
> despite Andrzej having left the community, we are not giving up on the encoder
> work. In 2025, we aim at working more seriously on the V4L2 spec, as just
> writing driver won't cut it. Each class of codecs needs a general workflow spec
> similar to what we have already for stateful encoder/decoder and stateless
> decoder.
> 
> - https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/dev-decoder.html
> - https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/dev-encoder.html
> - https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/dev-stateless-decoder.html
> 
> It is on top of this, that for each codec we have to add controls (mostly
> compound) specifics and details that suites stateless accelerators.
> 
> From a community stand point, the most important focus is to write and agree on
> spec and controls. Once we have that, vendors will be able to slowly move away
> from their custom solution, and compete on actual hardware rather then
> integration.
> 
> It is also time to start looking toward the future, since Hantro H1 is very
> limited and ancient encoder. On same brand, if someone could work on VC8000E
> shipped on IMX8M Plus, or Rockchip codecs, that will certainly help progress.

Marco Felsch and I recently started to work on stateless encoders, too.
Marco is working on a driver for VC8000E and I am working on a driver
for the Rockchip VEPU580. As user space, we are currently using the
GStreamer element from the draft merge request [0] on both drivers.

Michael

[0] https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5676

> We
> can also get inspiration from many other stateless encoding APIs now, notably
> VA, DXVA and Vulkan Video.
> 
> Of course, folks likes to know when this will happen, stateless decoders took 5
> years from start to the first codec being merged, hopefully we don't beat that
> record. I personally aim for producing work during the summer, and mostly focus
> on the spec. Its obvious for me that testing on H1 with a GStreamer
> implementation is the most productive, though I have strong interest in having
> an ecosystem of drivers. A second userspace implementation, perhaps ffmpeg ?,
> could also be useful.
> 
> If you'd like to take a bite, this is a good thread to discuss forward. Until
> the summer, I planned to reach to Paul, who made this great presentation [1] at
> FOSDEM last year and start moving the RFC into using these ideas. One of the
> biggest discussion is rate control, it is clear to me that modern HW integrated
> RC offloading, though some HW specific knobs or even firmware offloading, and
> this is what Paul has been putting some thought into.
> 
> If decoders have progressed so much in quality in the last few years, it is
> mostly before we have better ways to test them. It is also needed to start
> thinking how do we want to test our encoders. The stateful scene is not all
> green, with a very organic groth and difficult to unify set of encoders. And we
> have no metric of how good or bad they are either.