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传奇

tag-icon • tag-icon ffmpeg
传奇

ffmpeg 帮助页面顶部有一个图例，解释用于标记页面上列出的项目的大写字母的含义，例如ffmpeg -encoders打印以下图例：

Encoders:
 V..... = Video
 A..... = Audio
 S..... = Subtitle
 .F.... = Frame-level multithreading
 ..S... = Slice-level multithreading
 ...X.. = Codec is experimental
 ....B. = Supports draw_horiz_band
 .....D = Supports direct rendering method 1

但是，ffmpeg -h full没有图例，尽管选项（和参数）旁边有一个 10 个字符的字符串，其中EDFVASXRBT使用了字母。通过查看相应的选项，我猜是下面的选项，尽管我也不太确定和S，B并且XR总是一起使用，所以也许它们意味着实验性的，并且使用了两个字母，因为E已经使用了：

E......... = Muxer
.D........ = Demuxer
..F....... = Filter
...V...... = Video
....A..... = Audio
.....S.... = Subtitle
......X... = ?
.......R.. = ?
........B. = Bitstream
.........T = ?

那么，完整帮助页面中的字母是什么意思，并且该信息是否在文档的某处提供？

答案1

传奇

E.......... = Encoding or Muxing
.D......... = Decoding or Demuxing
..F........ = Filtering
...V....... = Video
....A...... = Audio
.....S..... = Subtitle
......X.... = Export
.......R... = Readonly
........B.. = Bitstream Filter
.........T. = Runtime (Indicates which filters support the `enable` option)
..........P = Deprecated

源代码参考

在libavutil/opt.c：

av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_ENCODING_PARAM) ? 'E' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_DECODING_PARAM) ? 'D' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_FILTERING_PARAM)? 'F' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_VIDEO_PARAM   ) ? 'V' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_AUDIO_PARAM   ) ? 'A' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_SUBTITLE_PARAM) ? 'S' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_EXPORT)     ? 'X' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_READONLY)       ? 'R' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_BSF_PARAM)      ? 'B' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_RUNTIME_PARAM)  ? 'T' : '.');
av_log(av_log_obj, AV_LOG_INFO, "%c", (opt->flags & AV_OPT_FLAG_DEPRECATED)     ? 'P' : '.');

在libavutil/opt.h：

#define AV_OPT_FLAG_ENCODING_PARAM  1   ///< a generic parameter which can be set by the user for muxing or encoding
#define AV_OPT_FLAG_DECODING_PARAM  2   ///< a generic parameter which can be set by the user for demuxing or decoding
#define AV_OPT_FLAG_AUDIO_PARAM     8
#define AV_OPT_FLAG_VIDEO_PARAM     16
#define AV_OPT_FLAG_SUBTITLE_PARAM  32
/**
 * The option is intended for exporting values to the caller.
 */
#define AV_OPT_FLAG_EXPORT          64
/**
 * The option may not be set through the AVOptions API, only read.
 * This flag only makes sense when AV_OPT_FLAG_EXPORT is also set.
 */
#define AV_OPT_FLAG_READONLY        128
#define AV_OPT_FLAG_BSF_PARAM       (1<<8) ///< a generic parameter which can be set by the user for bit stream filtering
#define AV_OPT_FLAG_RUNTIME_PARAM   (1<<15) ///< a generic parameter which can be set by the user at runtime
#define AV_OPT_FLAG_FILTERING_PARAM (1<<16) ///< a generic parameter which can be set by the user for filtering
#define AV_OPT_FLAG_DEPRECATED      (1<<17) ///< set if option is deprecated, users should refer to AVOption.help text for more information
#define AV_OPT_FLAG_CHILD_CONSTS    (1<<18) ///< set if option constants can also reside in child objects

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