ffmpeg - ffmpeg 命令中的 'dash' 选项有什么作用？

Question

-dash的作用或含义是什么？ ffmpeg 命令中的选项(提取 DASH 流的轨道)？例如这个:

ffmpeg -i in.video -vn -acodec libvorbis -ab 128k -dash 1 audio.webm

我在 ffmpeg documentation 中找不到任何相关信息.

Answer 1

webm muxer 可以选择告诉它处理是否可以与 DASH 流一起使用的文件。

要详细了解这意味着您可能需要查阅 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)