[FFmpeg-user] Capture multiple streams into same container?

[Moritz Barsnick]

On Tue, Jun 23, 2020 at 21:31:25 -0600, Simon Roberts wrote:
> But I have no clue how to start with this. I tried simply adding more input
> channels to my input specifications:
>
> ffmpeg -f decklink -i 'DeckLink Quad HDMI Recorder (1)' -f decklink -i
> 'DeckLink Quad HDMI Recorder (4)'  -c:v copy -c:a copy -metadata
> title=DeckLinkCapture  capture.mov

By default, ffmpeg only maps one of each stream type (video, audio,
subs), as described here:
https://ffmpeg.org/ffmpeg.html#Automatic-stream-selection

In your case, you need to explicitly map multiple inputs:

$ ffmpeg -f decklink -i 'DeckLink Quad HDMI Recorder (1)' -f decklink -i 'DeckLink Quad HDMI Recorder (4)' -map 0 -map 1 -c:v copy -c:a copy -metadata title=DeckLinkCapture capture.mov

(Note the "-map 0 -map 1" addition.)

Cheers,
Moritz