I have a ProRes MOV whose audio contains 8 channels of audio in a 7.1 surround layout (L R C LFE Ls Rs Lt RT).
I am preparing an H.264 MP4 for a media player that only supports AAC, and does not support 7.1, so I would like to map to 5.1, dropping ther 7th and 8th channels (Lt and Rt). Under normal circumstances I would just use the below for my transcode:
ffmpeg -i input_file -c:v libx264 -pix_fmt yuv420p -preset veryslow -crf 18 -c:a aac output_file
I've been looking at the documentation for audio layout manipulation, but am having trouble wrapping my head around it and they don't have a specific example of what I'm trying to do.
Do I need to export my audio to a WAV file first, or is there a way to manage the mapping in my transcode command? How can I map the existing first 6 channels to the new file?