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libaom 源码分析：aomdec.c 文件

article 2025/1/21 18:44:17

aomdec.c

功能：libaom 项目完成视频解码过程的 demo
文件位置：libaom/apps/aomdec.c

函数关系

在这里插入图片描述

命令行说明

终端输入 ./aomdec --help，输出如下，展示如何使用方法。

Usage: ./aomdec <options> filename

Options:
            --help                      Show usage options and exit
            --codec=<arg>               Codec to use
            --yv12                      Output raw YV12 frames
            --i420                      Output raw I420 frames
            --flipuv                    Flip the chroma planes in the output
            --rawvideo                  Output raw YUV frames
            --noblit                    Don't process the decoded frames
            --progress                  Show progress after each frame decodes
            --limit=<arg>               Stop decoding after n frames
            --skip=<arg>                Skip the first n input frames
            --summary                   Show timing summary
  -o <arg>, --output=<arg>              Output file name pattern (see below)
  -t <arg>, --threads=<arg>             Max threads to use
            --row-mt=<arg>              Enable row based multi-threading, default: 0
  -v,       --verbose                   Show version string
  -S,       --scale                     Scale output frames uniformly
            --frame-buffers=<arg>       Number of frame buffers to use
            --md5                       Compute the MD5 sum of the decoded frame
            --framestats=<arg>          Output per-frame stats (.csv format)
  -k,       --keep-going                (debug) Continue decoding after error
            --output-bit-depth=<arg>    Output bit-depth for decoded frames
            --annexb                    Bitstream is in Annex-B format
            --oppoint=<arg>             Select an operating point of a scalable bitstream
            --all-layers                Output all decoded frames of a scalable bitstream
            --skip-film-grain           Skip film grain application

Output File Patterns:

  The -o argument specifies the name of the file(s) to write to. If the
  argument does not include any escape characters, the output will be
  written to a single file. Otherwise, the filename will be calculated by
  expanding the following escape characters:

	%w   - Frame width
	%h   - Frame height
	%<n> - Frame number, zero padded to <n> places (1..9)

  Pattern arguments are only supported in conjunction with the --yv12 and
  --i420 options. If the -o option is not specified, the output will be
  directed to stdout.

Included decoders:

    av1    - AOMedia Project AV1 Decoder v3.8.3

usage_exit 函数就是完成demo 使用方法打印的函数，内部核心是调用了 show_help 函数，该函数利用参数变量shorthelp的取值 0/1 来控制命令行输入加参数和不加参数的情况。
show_help 函数的定义如下；其中 arg_show_usage 函数展示 all_args 的所有内容。

static void show_help(FILE *fout, int shorthelp) {
   
  fprintf(fout, "Usage: %s <options> filename\n\n", exec_name);

  if (shorthelp) {
   
    fprintf(fout, "Use --help to see the