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Reference Command Lines (High-quality and Performance)

Intel’s advanced software bitrate controller (dubbed “EncTools”) has been designed to boost GPU video quality for AVC, HEVC and AV1 using various compression efficiency technologies and content adaptive quality optimization tools while at the same time having minimal impact on the coding performance (speed). EncTools technology includes tools such as adaptive pyramid quantization, persistence adaptive quantization, look ahead, advanced scene change detection and more.

The recommended random access transcoding ffmpeg-qsv (Intel GPU integration with ffmpeg) command lines optimized for high quality and performance are given below:

AVC/H.264:

ffmpeg -hwaccel qsv -qsv_device ${DEVICE:-/dev/dri/renderD128} -c:v $inputcodec -extra_hw_frames 8 -an -i $input \
  -frames:v $numframes -c:v h264_qsv -preset $preset -profile:v high -async_depth 1 \
  -b:v $bitrate -maxrate $((2 * $bitrate)) -bitrate_limit 0 -bufsize $((4 * $bitrate)) \
  -rc_init_occupancy $((2 * $bitrate)) -low_power ${LOW_POWER:-true} \
  -look_ahead_depth 8 -extbrc 1 -b_strategy 1 \
  -adaptive_i 1 -adaptive_b 1 -bf 7 -refs 5 -g 256 -strict -1 \
  -fps_mode passthrough -y $output

HEVC/H.265:

ffmpeg -hwaccel qsv -qsv_device ${DEVICE:-/dev/dri/renderD128} -c:v $inputcodec -extra_hw_frames 8 -an -i $input \
  -frames:v $numframes -c:v hevc_qsv -preset $preset -profile:v main -async_depth 1 \
  -b:v $bitrate -maxrate $((2 * $bitrate)) -bufsize $((4 * $bitrate)) \
  -rc_init_occupancy $((2 * $bitrate)) -low_power ${LOW_POWER:-true} \
  -look_ahead_depth 8 -extbrc 1 -b_strategy 1 \
  -bf 7 -refs 4 -g 256 -idr_interval begin_only -strict -1 \
  -fps_mode passthrough -y $output

AV1:

ffmpeg -hwaccel qsv -qsv_device ${DEVICE:-/dev/dri/renderD128} -c:v $inputcodec -extra_hw_frames 8 -an -i $input \
  -frames:v $numframes -c:v av1_qsv -preset $preset -profile:v main -async_depth 1 \
  -b:v $bitrate -maxrate $((2 * bitrate)) -bufsize $((4 * bitrate)) \
  -rc_init_occupancy $((2 * bitrate)) -low_power ${LOW_POWER:-true} -look_ahead_depth 8 -extbrc 1 \
  -b_strategy 1 -adaptive_i 1 -adaptive_b 1 -bf 7 -g 256 -strict -1 \
  -fps_mode passthrough -y $output

Extra quality boost can be achieved with use of look ahead (by setting -look_ahead_depth 40 option) at the expense of a slight performance impact (10-20%). The use of -extra_hw_frames option is currently required for transcoding with look ahead due to the increased GPU memory requirements. Please set the value for -extra_hw_frames to be the same as the number of look ahead frames.

For best single stream performance or low density use case with high resolutions such as 4K, -async_depth 2 option is recommended (yielding only negligible quality loss compared to -async_depth 1).

Recommendations for more specific use cases as well as additional information on developer configurable bitrate controllers and available advanced coding options are provided in the supplementary Video Quality document.

For more details on ffmpeg-qsv supported features, see ffmpeg-qsv capabilites.

For more information on how to engage with Intel GPU encoding, decoding and transcoding as well as deal with multiple GPUs, please refer to ffmpeg-qsv multi-GPU selection document.

The recommended good practices are used throughout this project: in the demo examples as well as in the quality and performance measuring scripts. The following links provide additional information: