FFmpex.add_stream_specifier

You're seeing just the function add_stream_specifier, go back to FFmpex module for more information.

add_stream_specifier(command, opts)

add_stream_specifier(command :: FFmpex.Command.t(), opts :: Keyword.t()) ::
  FFmpex.Command.t()

Add a stream specifier to the most recent file. The stream specifier is used as a target for per-stream options.

add_stream_specifier(command, stream_type: :video)

:stream_index - 0-based integer index for the stream
:stream_type - One of :video, :video_without_pics, :audio, :subtitle, :data, :attachments
:program_id - ID for the program
:stream_id - Stream id (e.g. PID in MPEG-TS container)
:metadata_key - Match streams with the given metadata tag
:metadata_value - Match streams with the given metadata value. Must also specify :metadata_key.
:usable - Matches streams with usable configuration, the codec must be defined and the essential information such as video dimension or audio sample rate must be present.