Discussion:
[PATCH v2 0/7] Host1x IOMMU support + VIC support
(too old to reply)
Daniel Vetter
2016-12-14 14:48:55 UTC
Permalink
This series adds IOMMU support to Host1x and TegraDRM
and adds support for the VIC (Video Image Compositor)
host1x client. The series is available as a git repository at
git://github.com/cyndis/linux.git; branch vic-2.
A userspace test case for VIC can be found at
https://github.com/cyndis/drm/tree/work/tegra.
The testcase is in tests/tegra and is called submit_vic.
The testcase/TRM include full headers and documentation
to program the unit. The unit by itself, however, does not
readily map to existing userspace library interfaces, so
implementations for those are not provided.
Afaik libva has an entire pile of post-processing support. Pretty sure
other video transcode libraries have similar interfaces, so should all be
possible to implement this.
We don't have any actual video transcoding support though, so unless it's
possible to just implement a part of libva and defer the rest to some CPU
implementation, I don't see how this is useful. I suppose I could implement
a GStreamer plugin for colorspace conversion or resizing, since those are
very modular.
Hm, I guess the question then is, how did that get enabled?
What is "that"? I'm not exactly sure.
Our architecture is such that there's the VIC that handles colorspace
conversion, rescaling, blitting and can do some 2d postprocessing effects as
well.
Then there's the separate NVDEC that is a video bitstream decoder. There's
no support for that at the moment. I am working on the IP side of that.
The video processing pipeline is then such that NVDEC is fed the bitstream;
NVDEC outputs a YUV picture in a specific format; VIC takes that YUV picture
and converts/rescales it into the desired format. Or if we are encoding
video, VIC takes your RGB image, converts it into a format that NVENC
understands, and so on.
So with just VIC support, I could implement some simple 2D things. I don't
know if anyone would want to specifically use the VIC for those since
applications already have fast CPU algorithms. For the video pipeline using
VIC is nice since these units can synchronize work without CPU involvement
and when you're already using NVDEC or NVENC it's barely any extra effort to
involve VIC as well. It can also be useful in power usage sensitive
situations, but we aren't really fit for those situations with the upstream
kernel anyway :)
Ah I thought the nvdec was already enabled, since for i915 that's how we
went about things (we have a pretty much exactly matching split in the
various video related engines). But if that's not there yet then no
worries, all fine.
Since you do seem to plan to enable everything anyway, might be worth it
to go directly with something like libva or libvdpau or whatever the cool
thing is. libva is my recommendation since it works on non-X11 too afaik,
but I have 0 clue. And might be worth it to check out whether you can't do
a super-basic libva driver that only does the post processing stuff. With
libva you can import/export images, so it might be possible even ... And
directly doing the full video engine support instead of a one-off in
gstreamer sounds more sensible to me.
Silly me forgot to add the experts, i.e. Sean (current libva
maintainer) and libva mailing lists.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
Sean V Kelley
2016-12-15 02:52:17 UTC
Permalink
Hi,
Post by Daniel Vetter
This series adds IOMMU support to Host1x and TegraDRM
and adds support for the VIC (Video Image Compositor)
host1x client. The series is available as a git repository at
git://github.com/cyndis/linux.git; branch vic-2.
A userspace test case for VIC can be found at
https://github.com/cyndis/drm/tree/work/tegra.
The testcase is in tests/tegra and is called submit_vic.
The testcase/TRM include full headers and documentation
to program the unit. The unit by itself, however, does not
readily map to existing userspace library interfaces, so
implementations for those are not provided.
Afaik libva has an entire pile of post-processing support. Pretty sure
other video transcode libraries have similar interfaces, so should all be
possible to implement this.
We don't have any actual video transcoding support though, so unless it's
possible to just implement a part of libva and defer the rest to some CPU
implementation, I don't see how this is useful. I suppose I could implement
a GStreamer plugin for colorspace conversion or resizing, since those are
very modular.
Hm, I guess the question then is, how did that get enabled?
What is "that"? I'm not exactly sure.
Our architecture is such that there's the VIC that handles colorspace
conversion, rescaling, blitting and can do some 2d postprocessing effects as
well.
Then there's the separate NVDEC that is a video bitstream decoder. There's
no support for that at the moment. I am working on the IP side of that.
The video processing pipeline is then such that NVDEC is fed the bitstream;
NVDEC outputs a YUV picture in a specific format; VIC takes that YUV picture
and converts/rescales it into the desired format. Or if we are encoding
video, VIC takes your RGB image, converts it into a format that NVENC
understands, and so on.
So with just VIC support, I could implement some simple 2D things. I don't
know if anyone would want to specifically use the VIC for those since
applications already have fast CPU algorithms. For the video pipeline using
VIC is nice since these units can synchronize work without CPU involvement
and when you're already using NVDEC or NVENC it's barely any extra effort to
involve VIC as well. It can also be useful in power usage sensitive
situations, but we aren't really fit for those situations with the upstream
kernel anyway :)
Ah I thought the nvdec was already enabled, since for i915 that's how we
went about things (we have a pretty much exactly matching split in the
various video related engines). But if that's not there yet then no
worries, all fine.
Since you do seem to plan to enable everything anyway, might be worth it
to go directly with something like libva or libvdpau or whatever the cool
thing is. libva is my recommendation since it works on non-X11 too afaik,
but I have 0 clue. And might be worth it to check out whether you can't do
a super-basic libva driver that only does the post processing stuff. With
libva you can import/export images, so it might be possible even ... And
directly doing the full video engine support instead of a one-off in
gstreamer sounds more sensible to me.
Silly me forgot to add the experts, i.e. Sean (current libva
maintainer) and libva mailing lists.
-Daniel
From a purely VPP standpoint libva is something that would give VIC a readily available API in user space. You don’t have to have a transcoding use case to leverage VPP with a surface with VA-API. On top of that we do support DMA but import and export to provide flexibility in sharing the memory. It’s entirely possible to support a subset of entry points (say VPP only) for VA-API through Libva and share that information in a query on the config say for your applications. We do that all the time with various backends having feature subsets such as our hybrid Intel driver, or the IMG based PVR driver. I believe there is also a Rock-Chip project experimenting with Libva for their media driver.

I’ll take a look at your link.

Sean

Intel, Corp.
Post by Daniel Vetter
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
_______________________________________________
Libva mailing list
https://lists.freedesktop.org/mailman/listinfo/libva
Loading...