[ffmpeg命令中的-dash
选项的作用或含义是什么(提取DASH流的轨道)?例如这一个:
ffmpeg -i in.video -vn -acodec libvorbis -ab 128k -dash 1 audio.webm
我在ffmpeg documentation中找不到关于它的任何东西。
这是webm混合器的一个选项,告诉它处理可以与DASH流一起使用或不与DASH流一起使用的文件。
要详细了解这意味着什么,您可能必须参考ffmpeg源代码https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/matroskaenc.c搜索is_dash
。
$ ffmpeg -help muxer=webm
Muxer webm [WebM]:
Common extensions: webm.
Mime type: video/webm.
Default video codec: vp9.
Default audio codec: opus.
Default subtitle codec: webvtt.
webm muxer AVOptions:
-reserve_index_space <int> E........ Reserve a given amount of space (in bytes) at the beginning of the file for the index (cues). (from 0 to INT_MAX) (default 0)
-cluster_size_limit <int> E........ Store at most the provided amount of bytes in a cluster. (from -1 to INT_MAX) (default -1)
-cluster_time_limit <int64> E........ Store at most the provided number of milliseconds in a cluster. (from -1 to I64_MAX) (default -1)
-dash <boolean> E........ Create a WebM file conforming to WebM DASH specification (default false)
-dash_track_number <int> E........ Track number for the DASH stream (from 0 to 127) (default 1)
-live <boolean> E........ Write files assuming it is a live stream. (default false)
-allow_raw_vfw <boolean> E........ allow RAW VFW mode (default false)
-write_crc32 <boolean> E........ write a CRC32 element inside every Level 1 element (default true)