vvenc和vvdec

Posted 2021-08-17 Dillon2015

VVC是最新一代视频编码标准，相比于HEVC在相同质量下能节省50%的码率。VTM是VVC的官方参考软件，由于VVC集成了大量新的编码工具导致复杂度也急剧上升，VTM的编码速度也非常慢。

Fraunhofer 开发了速度比VTM更快和更实用的VVC编码器和解码器。分别为VVenC和VVdeC，项目链接如下：

VVenC：https://github.com/fraunhoferhhi/vvenc

VVdeC：https://github.com/fraunhoferhhi/vvdec

两个项目编译都非常简单，此次略去编译过程。

VVenC

VVenC编译完成之后会产生两个可执行文件，分别是标准编码器vvencapp和全功能的专业编码器vvencFFapp。

标准编码器vvencapp

vvencapp有5个预定义的preset (faster, fast, medium, slow, slower)，其中最慢档preset的编码速度最慢但是编码质量最好，最快档preset的编码速度最快但编码质量最差 。vvencapp的主要，命令行参数如下：

OPTION	DEFAULT	DESCRIPTION
--help,-h	-	Show basic help
--input,-i <str>	-	Raw yuv input file or '-' for reading from stdin
--size,-s <wxh>	1920x1080	Input file resolution (width x height)
--framerate,-r <int>	60	Temporal rate of input file. Required for VBR encoding and calculation of output bit-rate. Also recommended with perceptual QP adaptation (see --qpa option below).
--format,-c <str>	yuv420	Set input format to YUV 4:2:0 8bit (yuv420) or YUV 4:2:0 10bit (yuv420_10)
--output,-o <str>	not set	Bit-stream output file
--preset <str>	medium	Preset for specific encoding setting (faster, fast, medium, slow, slower)
--qp,-q <int>	32	Quantization parameter (0..63)
--bitrate <int>	0	Bitrate for rate control (0: constant-QP encoding without rate control, otherwise bits per second). Rate control requires correct --framerate (see option above).
--passes,-p <int>	2	Number of rate control passes (1: single-pass rate control, 2: two-pass rate control)
--qpa <int>	1	Perceptual QP adaptation (QPA) to improve subjective video quality (0: off, 1: on)
--refreshsec,-rs <int>	1	Intra period/refresh in seconds
--threads,-t <int>	size >= 1280x720: 8, else: 4	Number of threads (1-N)
--hdr <str>	off	HDR mode (+ SEI messages) + BT.709 or BT.2020 color space (off, pq, pq_2020, hlg, hlg_2020)

命令行示例：假设输入的序列采样格式为YUV420，位深为8比特，分辨率为176x144，则可以采用下面的命令使用medium preset进行编码：

vvencapp --preset medium -i [e-mail] -s 176x144 -o str.266

专业编码器vvencFFapp

vvencFFapp的使用方式类似于VTM，也是使用配置文件进行。大部分编码参数和VTM保持一致，但是某些参数会增加额外的可选模式。其配置文件可在cfg文件夹下找到。配置文件描述如下：

CONFIGURATION FILE	DESCRIPTION
sequence.cfg	Sequence specific configuration parameters. Must be always adapted to the input sequence.
randomaccess_faster.cfg randomaccess_fast.cfg randomaccess_medium.cfg randomaccess_slow.cfg randomaccess_slower.cfg	Random access configuration for different presets. Each configuration file corresponds to one of the 5 preset modes.
qpa.cfg	Perceptually optimized QPA configuration file.
rc1p.cfg	Single pass rate control configuration, overriding default fix QP setup.
rc2p.cfg	Two pass rate control configuration, overriding default fix QP setup.

使用方式如下：

vvencFFapp -c randomaccess_medium.cfg -c sequence.cfg

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