An output's choice of source and encoding.

FFix.Encoder helpers and FFix.stream_copy/1 create mappings for you. FFix.output/3 wraps bare streams in mappings using FFmpeg's default encoding. Use new/2 when building mappings directly or reusing an encoder configuration.

A mapping has a source, an encoding, and an optional output-local name. Encoding is an FFix.Encoder configuration, :copy, or nil for FFmpeg's defaults. See FFix.Command.Output for names and option callbacks.

Encoding several tracks

A mapping of FFix.audio(input, :all) can create several audio tracks. The same encoding applies to every selected track. Different settings need separately indexed selections:

alias FFix.Encoder
source = FFix.input("interview.mkv")

output =
  FFix.output([
    FFix.stream_copy(FFix.audio(source, :all)),
    Encoder.libx264(FFix.video(source, 0), crf: 20),
    Encoder.libx264(FFix.video(source, 0), crf: 28)
  ], "qualities.mkv")

FFix.command(output)

Both video settings follow their respective mappings, even though the audio selection's track count is unknown. FFix uses video-relative option scopes in this case. When every mapping selects one stream, it uses absolute output indexes. Indexes restart for each destination.

Within a media type, broad selections must share the same encoding policy and options. Mixing all-audio copy with an individually encoded audio track is ambiguous; select each audio track explicitly instead. Whole-input and raw-string queries have unknown media, so layouts containing them support leaving every mapping unconfigured or copying every mapping.

Reusing a direct input stream creates another output use with its own encoding. To reuse a filtered stream, first branch it with FFix.Filter.split/2 or FFix.Filter.asplit/2.