The provided `ffmpeg` command processes multiple input files and generates...

The provided ffmpeg command processes multiple input files and generates different output files based on specified stream mappings and codec options. Let’s break this down step by step:

Command:

ffmpeg -i A.avi -i B.mp4 out1.mkv out2.wav -map 1:a -c:a copy out3.mov

1. Input Files:

• -i A.avi: Specifies the first input file A.avi.
• -i B.mp4: Specifies the second input file B.mp4.

2. Output Files:

• out1.mkv: First output file. No specific mapping or codec settings are applied here, so FFmpeg will likely use default streams and encoding from the first input (unless further options specific to this output are provided earlier or omitted in the full command).
• out2.wav: Second output file. As with the above, this file is created from defaults unless explicitly mapped streams or codec configurations control it.

3. Mapping Streams (-map 1:a):

• -map 1:a: Maps the audio stream (a) from the second input (B.mp4) to subsequent output files.
  • This means streams for outputs processed afterward will use the audio from B.mp4.

4. Codec Settings (-c:a copy):

• -c:a copy: Specifies that audio streams should be copied as-is (without re-encoding) for the next outputs.

5. Third Output (out3.mov):

• out3.mov: This file will receive the mapped audio (1:a, from B.mp4) in its output. The audio codec will be unchanged because of the -c:a copy option.

Key Effects of the Command:

1. Processes two input files (A.avi and B.mp4).
2. Creates the following outputs:
   • out1.mkv: Likely uses default streams and encoding options.
   • out2.wav: Again, likely uses defaults unless further mapping applies.
   • out3.mov: Contains the audio stream from B.mp4 (-map 1:a), copied directly without re-encoding (-c:a copy).

Concerns:

There is some inconsistency or ambiguity in this command. For example:

• out3.mov relies on -map 1:a explicitly, but it’s unclear how out1.mkv and out2.wav are handled stream-wise.
• The interaction between default behaviors and explicit mappings may not lead to the intended output.

Fine-tuning -map options for each output is often necessary for precise stream control when generating multiple outputs.