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53 lines
2.3 KiB
Markdown
53 lines
2.3 KiB
Markdown
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# Libva Rust wrapper
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Rust wrapper for libva. Provides safe libva abstractions for use within Rust code using its own
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bindgen-generated bindings.
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This crate is used as part of the VirtIO Video VA-API backend. VA-API uses the GPU to perform the
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actual decoding/encoding of frames. In doing so, it frees the CPU for other uses and reduces power
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usage in the system. Hardware accelerated media workflows also tend to be faster than their software
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counterparts.
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Note: This create requires the native [libva](https://github.com/intel/libva) library at link time.
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It also requires a VA-API driver to be installed on the system. The VA-API driver to use depends on
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the underlying hardware, e.g.: the implementation for Intel hardware is in
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[intel-media-driver](https://github.com/intel/media-driver), whereas AMD hardware will depend on
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[Mesa](https://gitlab.freedesktop.org/mesa/mesa).
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An easy way to see whether everything is in order is to run the `vainfo` utility. This is usually
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packaged with `libva-utils` or as a standalone package in some distributions. `vainfo` will print
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the VA-API version, the driver string, and a list of supported profiles and endpoints, i.e.:
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```
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vainfo: VA-API version: 1.13 (libva 2.13.0)
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vainfo: Driver version: Intel iHD driver for Intel(R) Gen Graphics - 22.2.2 ()
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vainfo: Supported profile and entrypoints
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VAProfileNone : VAEntrypointVideoProc
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VAProfileNone : VAEntrypointStats
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VAProfileMPEG2Simple : VAEntrypointVLD
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VAProfileMPEG2Simple : VAEntrypointEncSlice
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VAProfileMPEG2Main : VAEntrypointVLD
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VAProfileMPEG2Main : VAEntrypointEncSlice
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VAProfileH264Main : VAEntrypointVLD
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etc
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```
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For decoding, the desired profile must be supported under `VAEntrypointVLD`. For example, in order
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to decode VP8 media, this line must be present in the output of `vainfo`:
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```
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VAProfileVP8Version0_3 : VAEntrypointVLD
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```
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Whereas to decode H264 Main profile media, this line must be present:
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```
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VAProfileH264Main : VAEntrypointVLD
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```
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For more information on VA-API and its usage within ChromeOS, see
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[this guide](https://chromium.googlesource.com/chromium/src/+/master/docs/gpu/vaapi.md).
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For a brief introduction on how to use this crate, see the `libva_utils_mpeg2vldemo` test under
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src/lib.rs.
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