Hw. acceleration support

UltraGrid supports video encoding and decoding libavcodec HW acceleration with VA-API and vendor specific APIs (VDPAU, QuickSync, AMF, VideoToolbox, NVENC/CUVID). Currently the acceleration works best with VA-API on Intel and VDPAU on Nvidia proprietary drivers.

Table of Contents

• Table of Contents
• AMD support
• QuickSync
  • Software requirements
    • Debugging
  • Intel XE-Lp Alder Lake-P Graphics (Gen 12)
    • Encode
      • HEVC
    • Decode
      • HEVC
  • Intel Arc A770 (DG2, Gen 12.7)
• Vulkan

AMD support

If not stated otherwise, encode/decode with H.264 and HEVC was tested in the setups below.

GPU	OS	API	UG version	status
RX 580	Ubuntu 18.04	VA-API	pre-1.8	+/- works1,2
RX 580	Ubuntu 18.04	VDPAU	pre-1.8	works, decode only³
RX 580	Windows 10	AMF⁴	pre-1.8	works, encode only
RX 580	Arch 10/2023	VA-API	1.8.5	encode works⁵
RX 580	Arch 10/2023	VA-API	ac110f1	works⁵
RX 7600	Arch 10/2023	VA-API	1.8.5	encode works
RX 7600	Arch 10/2023	VA-API	ac110f1	works

¹ encoded stream H.264 was not decodable until amdgpu-pro-19.20-812932-ubuntu-18.04 and kernel 5.0.0-17-generic installed, HEVC broken

² H.264 decoded but wrong colors in chroma

³ works in copy mode only

⁴ encode doesn't support intra-refresh (setting intra_refresh_mb doesn't seem to help; use quality constrain parameter - :qp_i=36, which hand solves bitrate variance but causes artifacts on the I-frames)

⁵ slices are not supported by the encoder, :slices=1 need to be set

QuickSync

Software requirements

• Debian 12/Ubuntu 24.04 - libmfx-gen1.2 and intel-media-va-driver-non-free installed
• user should be a member of render group (the output of cmd groups should contain "render", if not, use sudo gpasswd -a <user> render; newgrp render)

Troubleshooting

1. Check the output of vpl-inspect (package onevpl-tools) and vainfo.
2. try to set LIBVA_DRIVER_NAME=iHD
3. with an older distro, build own libvpl (instead of package libmfx-gen1.2), media driver (instead of intel-media-va-driver-non-free, also see the notes)
4. if building own FFmpeg, libvpl-dev is required

Intel XE-Lp Alder Lake-P Graphics (Gen 12)

• CPU utilization seem to be rather even when using acceleration (some 2.5 core for one direction)

Encode

HEVC

• works using XV30 (10-bit YCbCr 4:4:4), yuyv422 or vuya (8-bit YCbCr 4:4:4). y210le (10-bit 4:2:2) can be used if intra refresh is disabled
• X2RGB10 (10-bit RGB) works but converts RGB to YCbCr internally
• bgra works when enabled HuC mode and low_power is enabled (VA-API entry point VAEntrypointEncSliceLP) – -c libavcodec:encoder=hevc_qsv:low_power=1

Decode

HEVC

• 10 and 12-bit YCbCr 4:4:4 works correctly
• RGB formats don't currently work - QSV decompresses them correctly as RGB but presents them (incorrectly) in a YCbCr container/pixelfmt xv36, xv30 or vuya (depending on bit-depth)
• UHD 4K resolution and YUV 4:4:4 (or equivalent RGB) causes "GPU Hang" errors, reported here and here; does occur with kernel 5.15 but not 6.0 regardless the in HuC mode
• not sure if there are not artifacts

The above color space issues can be tracked here.

Intel Arc A770 (DG2, Gen 12.7)

Ubuntu at least 23.10 is recommended (unless drivers from Intel are used).

Vulkan

UltraGrid supports Vulkan decode through ffmpeg. Currently only copy mode is supported (the hw. frames are transferred to cpu managed memory). To use this, UltraGrid needs to be build with a recent enough ffmpeg (release 6.2) and the system needs to have a recent version of the mesa package installed (23.1 for H.264 and 23.2 for HEVC).

The implementation has been observed to work on Intel and Nvidia GPUs. Currently, when running on Intel GPUs, the environment variable ANV_VIDEO_DECODE=1 needs to be set to enable Vulkan decode support in the driver.