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Scalable Video Technology for AV1 Encoder (SVT-AV1 Encoder) User Guide

Introduction

This document describes how to use the Scalable Video Technology for AV1 Encoder (SVT-AV1). In particular, this user guide describes how to run the sample application with the respective dynamically linked library.

Sample Application Guide

This section describes how to run the sample encoder application that uses the SVT-AV1 Encoder library. It describes the input video format, the command line input parameters and the resulting outputs.

Input Video Format

The SVT-AV1 Encoder supports the following input formats:

8-bit yuv420p

10-bit yuv420p10le

Compressed 10-bit format

In order to reduce the size of the input original YUV file, the SVT-AV1 Encoder uses a compressed 10-bit format allowing the software to achieve a higher speed and channel density levels. The conversion between the 10-bit yuv420p10le and the compressed 10-bit format is a lossless operation and is performed using the following steps.

Unpack the 10-bit picture

This step consists of separating the 10 bit video samples into 8 bit and 2 bit planes so that each 10-bit picture will be represented as two separate pictures as shown in the figure below. As a result of the operation, the 2 least significant bits of the 10 bits will be written into a full byte.

10-bit yuv420p10le unpacked

Compress the 2 bit Plane

The unpacking steps separates the 10bits into a group of 8 bits and a group of 2 bits, where the 2 bits are stored in a byte. In this step, every group of consecutive 4 bytes, each containing 2bits from the unpacking step, are compressed into one byte. As a result, each 10bit picture will be represented as two separate pictures as shown in the figure below.

10-bit yuv420p10le compressed

Running the encoder

This section describes how to run the sample encoder application SvtAv1EncApp.exe (on Windows*) or SvtAv1EncApp (on Linux*) from the command line, including descriptions of the most commonly used input parameters and outputs.

The sample application typically takes the following command line parameters:

-c filename [Optional]

A text file that contains encoder parameters such as input file name, quantization parameter etc. Refer to the comments in the Config/Sample.cfg for specific details. The list of encoder parameters are also listed below. Note that command line parameters take precedence over the parameters included in the configuration file when there is a conflict.

-i filename [Required]

A YUV file (e.g. 8 bit 4:2:0 planar) containing the video sequence that will be encoded. The dimensions of each image are specified by -w and -h as indicated below.

-b filename [Optional]

The resulting encoded bit stream file in binary format. If none specified, no output bit stream will be produced by the encoder.

The output format can be selected with --ivf (default) for IVF container or --obu for raw OBU (Open Bitstream Units) without container framing. The format is also auto-detected from the file extension: .ivf produces IVF output, .obu produces raw OBU output. Explicit --ivf/--obu flags override extension-based auto-detection.

-w integer [Required]

The width of each input image in units of picture luma pixels, e.g. 1920

-h integer [Required]]

The height of each input image in units of picture luma pixels, e.g. 1080

-n integer [Optional]

The number of frames of the sequence to encode. e.g. 100. If the input frame count is larger than the number of frames in the input video, the encoder will loopback to the first frame when it is done.

--keyint integer [Optional]

The keyint defines the display order location at which the encoder would insert a keyframe. It is recommended to use a value that is (a multiple of the mini GOP size (default 16)) + 1 so that the keyframe does not break a mini GOP formation. When using forward frame, it is recommended that the keyint value is placed at a multiple of mini-gop size. The mini-gop size is measured by 1 << hierarchical-levels.

SvtAv1EncApp only: optionally accepts a s suffix to indicate to use keyint * frame-rate as the keyint value. e.g. --keyint 5s for 5 seconds

--rc integer [Optional]

The rc token sets the bitrate control encoding mode [0: Constant QP OR Constant Rate Factor, 1: Variable Bitrate, 2: Constant Bitrate].

With --rc set to 0, CQP (fixed qp offsets regardless of the content) mode is enabled using --aq-mode 0, else CRF mode (default) will be used. If --crf is set, then aq-mode will be forced to 2, however, if -q/--qp is set, then the encoder will use whatever is set for aq-mode.

If a qp/crf value is not specified, a default value is assigned (35).

Sample command lines

Here are some sample encode command lines

1 pass CRF at maximum speed for a 1920x1080 input

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --crf 30 --preset 12 -b output.ivf

1 pass VBR 1000 Kbps at medium speed for a 1920x1080 input

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --rc 1 --tbr 1000 --preset 5 -b output.ivf

Multi-pass VBR 1000 Kbps at maximum quality for a 1920x1080 input

Single command line :

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --rc 1 --tbr 1000 --preset 0 --passes 2 --stats stat_file.stat -b output.ivf

or

Multiple command lines :

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --rc 1 --tbr 1000 --preset 0 --pass 1 --stats stat_file.stat SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --rc 1 --tbr 1000 --preset 0 --pass 2 --stats stat_file.stat SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --rc 1 --tbr 1000 --preset 0 --pass 3 --stats stat_file.stat -b output.ivf

1 pass CRF at maximum speed for a 1920x1080 input with full range video signal

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --crf 30 --preset 12 --color-range full -b output.ivf

1 pass CRF at maximum speed for a 1920x1080 input with colorimetry set to BT.709

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --crf 30 --preset 12 --color-primaries bt709 --transfer-characteristics bt709 --matrix-coefficients bt709 -b output.ivf

1 pass CRF with raw OBU output (no IVF container)

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --crf 30 --preset 8 -b output.obu

or equivalently using the --obu flag:

SvtAv1EncApp -i input.yuv -w 1920 -h 1080 --crf 30 --preset 8 --obu -b output.ivf