[FFmpeg-user] Audio channels mapping - Decklink SDI input

Mustafa Al Ani mustafalani at gmail.com
Thu Nov 8 02:47:32 EET 2018

Hi all,

I'm trying to encode Decklink SDI input and stream it to NDI and keep the
audio layout as is.

The SDI signal has 8 audio channels with the following layout:
1,2 Stereo
3,4 Stereo
5,6 Dolby
7,8 Stereo

What I need to do is to passthrough all audio channels and to keep the
layout as is.

Tried "-ac 8 -acodec copy" but it doesn't seem to be working.
Maybe I need to use something like "-map_channel" and then to define the
audio output layout BUT to do so I need to know "stream_specifier.channel_id"
and when I ffprobe the SDI input I get "channel_layout=unknown" which I
think is a known issue with Decklink cards according to BM support forums

> There is no format detection options for audio capture to determine the
> number of audio channels provided by the video source.

Can anyone help with the correct command to passthrough the audio channels?
your inputs are highly appreciated.!


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