5482210941
In preparation of patches that will allow V4L2 decoding to work by default on Linux. The VA-API and V4L2 backends provide essenitaly the same output - DMABufs in formats like NV12/P010 etc. - and face similar restrictions e.g. GL driver features. It therefore makes sense to have the same media switches and in fact some of them - most importantly `VaapiVideoDecodeLinux` - already apply to V4L2. Thus in order to reduce confusion and avoid code duplication, rename some of the `Vaapi` swiches used in common code to `Accelerated` but keep the `Linux` suffix, making it clearer to what they apply. Also ensure they are used for both APIs the same way and update the `vaapi.md`. Finally, add `AcceleratedVideoDecodeLinuxZeroCopyGL` to the VA-API documentation. Bug: b:334110478 Change-Id: Iea58966d6ab94ce995defb1cf1099dd9ba9fae26 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5893615 Reviewed-by: Sean Topping <seantopping@chromium.org> Reviewed-by: Kentaro Hara <haraken@chromium.org> Reviewed-by: Fritz Koenig <frkoenig@chromium.org> Commit-Queue: Fritz Koenig <frkoenig@chromium.org> Cr-Commit-Position: refs/heads/main@{#1363231}
174 lines
7.7 KiB
Markdown
174 lines
7.7 KiB
Markdown
# VA-API
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This page documents tracing and debugging the Video Acceleration API (VaAPI or
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VA-API) on ChromeOS. VA-API is an open-source library and API specification,
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providing access to graphics hardware acceleration capabilities for video and
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image processing. VA-API is used on ChromeOS on both Intel and AMD platforms.
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[TOC]
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VA-API is implemented by a generic `libva` library, developed upstream on
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the [VaAPI GitHub repository], from which ChromeOS is a downstream client via
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the [libva] package. Several backends are available for it, notably the legacy
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[Intel i965], the modern [Intel iHD] and the [AMD].
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[VaAPI GitHub repository]: https://github.com/intel/libva
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[libva]: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/main/x11-libs/libva/
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[Intel i965]: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/main/x11-libs/libva-intel-driver/
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[Intel iHD]: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/main/x11-libs/libva-intel-media-driver/
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[AMD]: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/main/media-libs/libva-amdgpu-driver/
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## `libva` tracing
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The environment variable `LIBVA_TRACE=/path/to/file` can be exposed to libva to
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store tracing information (see [va_trace.c]). `libva` will create a number of
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e.g. `libva.log.033807.thd-0x00000b25 ` files (one per thread) with a list of
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the actions taken and semi-disassembled parameters.
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[va_trace.c]: https://github.com/intel/libva/blob/64520e9ec90ed30e016d7c633d746b3bf538c702/va/va_trace.c#L59
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## `libva` logging
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The environment variable `LIBVA_MESSAGING_LEVEL=0` (or `1` or `2`) can be used
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to configure increasing logging verbosity to stdout (see [va.c]). Chromium uses
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a level `0` by default in `vaapi_wrapper.cc`.
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[va.c]: https://github.com/intel/libva/blob/2ece7099061ba4ea821545c8b6712b5c421c4dea/va/va.c#L194
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## Tracing power consumption
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Power consumption is available on ChromeOS test/dev images via the command line
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binary [`dump_intel_rapl_consumption`]; this tool averages the power
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consumption of the four SoC domains over a configurable period of time, usually
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a few seconds. These domains are, in the order presented by the tool:
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* `pkg`: estimated power consumption of the whole SoC; in particular, this is a
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superset of pp0 and pp1, including all accessory silicon, e.g. video
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processing.
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* `pp0`: CPU set.
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* `pp1`/`gfx`: Integrated GPU or GPUs.
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* `dram`: estimated power consumption of the DRAM, from the bus activity.
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`dump_intel_rapl_consumption` results should be a subset and of the same
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numerical value as those produced with e.g. `turbostat`. Note that despite the
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name, the tool works on AMD platforms as well, since they provide the same type
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of measurement registers, albeit a subset of Intel's. Googlers can read more
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about this topic under [go/power-consumption-meas-in-intel].
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`dump_intel_rapl_consumption` is usually run while a given workload is active
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(e.g. a video playback) with an interval larger than a second to smooth out all
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kinds of system services that would show up in smaller periods, e.g. WiFi.
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```shell
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dump_intel_rapl_consumption --interval_ms=2000 --repeat --verbose
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```
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E.g. on a nocturne main1, the average power consumption while playing back the
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first minute of a 1080p VP9 [video], the average consumptions in watts are:
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|`pkg` |`pp0` |`pp1`/`gfx` |`dram`|
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| ---: | ---: | ---: | ---: |
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| 2.63 | 1.44 | 0.29 | 0.87 |
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As can be seen, `pkg` ~= `pp0` + `pp1` + 1W, this extra watt is the cost of all
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the associated silicon, e.g. bridges, bus controllers, caches, and the media
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processing engine.
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[`dump_intel_rapl_consumption`]: https://chromium.googlesource.com/chromiumos/platform2/+/main/power_manager/tools/dump_intel_rapl_consumption.cc
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[video]: https://commons.wikimedia.org/wiki/File:Big_Buck_Bunny_4K.webm
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[go/power-consumption-meas-in-intel]: http://go/power-consumption-meas-in-intel
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## Verifying VaAPI installation and usage
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### <a name="verify-driver"></a> Verify the VaAPI is correctly installed and can be loaded
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`vainfo` is a small command line utility used to enumerate the supported
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operation modes; it's developed in the [libva-utils] repository, but more
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concretely available on ChromeOS dev images ([media-video/libva-utils] package)
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and under Debian systems ([vainfo]). `vainfo` will try to load the appropriate
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backend driver for the system and/or GPUs and fail if it cannot find/load it.
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[libva-utils]: https://github.com/intel/libva-utils
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[media-video/libva-utils]: https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/main/media-video/libva-utils
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[vainfo]: https://packages.debian.org/sid/main/vainfo
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### <a name="verify-vaapi"></a> Verify the VaAPI supports and/or uses a given codec
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A few steps are customary to verify the support and use of a given codec.
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To verify that the build and platform supports video acceleration, launch
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Chromium and navigate to `chrome://gpu`, then:
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* Search for the "Video Acceleration Information" Section: this should
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enumerate the available accelerated codecs and resolutions.
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* If this section is empty, oftentimes the "Log Messages" Section immediately
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below might indicate an associated error, e.g.:
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> vaInitialize failed: unknown libva error
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that can usually be reproduced with `vainfo`, see the [previous
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section](#verify-driver).
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To verify that a given video is being played back using the accelerated video
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decoding backend:
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* Navigate to a url that causes a video to be played. Leave it playing.
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* Navigate to the `chrome://media-internals` tab.
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* Find the entry associated to the video-playing tab.
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* Scroll down to "`Player Properties`" and check the "`video_decoder`" entry:
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it should say "GpuVideoDecoder".
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## VaAPI on Linux
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VA-API on Linux is not supported, but it can be enabled using the flags below,
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and it might work on certain configurations -- but there's no guarantees.
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* To support proprietary codecs such as, e.g. H264/AVC1, add the options
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`proprietary_codecs = true` and `ffmpeg_branding = "Chrome"` to the GN args
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(please refer to the [Setting up the build] Section).
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* Build Chromium as usual.
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At this point you should make sure the appropriate VA driver backend is working
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correctly; try running `vainfo` from the command line and verify no errors show
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up, see the [previous section](#verify-driver).
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The following feature switch controls video encoding (see [media
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switches](https://source.chromium.org/chromium/chromium/src/+/main:media/base/media_switches.cc)
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for more details):
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* `--enable-features=AcceleratedVideoEncoder`
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The following two arguments are optional:
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* `--ignore-gpu-blocklist`
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* `--disable-gpu-driver-bug-workaround`
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The following feature can improve performance when using EGL/Wayland:
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* `--enable-features=AcceleratedVideoDecodeLinuxZeroCopyGL`
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The NVIDIA VaAPI drivers are known to not support Chromium (see
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[crbug.com/1492880](https://crbug.com/1492880)). This feature switch is
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provided for developers to test VaAPI drivers on NVIDIA GPUs:
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* `--enable-features=VaapiOnNvidiaGPUs`, disabled by default
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### VaAPI on Linux with OpenGL
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```shell
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./out/gn/chrome --use-gl=angle --use-angle=gl \
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--enable-features=AcceleratedVideoEncoder,AcceleratedVideoDecodeLinuxGL,VaapiOnNvidiaGPUs \
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--ignore-gpu-blocklist --disable-gpu-driver-bug-workaround
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```
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### VaAPI on Linux with Vulkan
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```shell
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./out/gn/chrome --use-gl=angle --use-angle=vulkan \
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--enable-features=AcceleratedVideoEncoder,VaapiOnNvidiaGPUs,VaapiIgnoreDriverChecks,Vulkan,DefaultANGLEVulkan,VulkanFromANGLE \
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--ignore-gpu-blocklist --disable-gpu-driver-bug-workaround
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```
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Refer to the [previous section](#verify-vaapi) to verify support and use of the VaAPI.
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[Setting up the build]: https://chromium.googlesource.com/chromium/src/+/HEAD/docs/linux/build_instructions.md#setting-up-the-build
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