Ffmpeg multi channel surround to flac

I am trying to convert/compress a lossless source to flac and have it a smaller output size.

ffmpeg -i "S01E01 (AV1).mkv" -map 0 -map_chapters 0 -c:v copy -c:s copy -c:a flac -compression_level 12 -af "channelmap=channel_layout=5.1" -ab 1024 "S01E01(AV1)(FLAC).mkv"

What is wrong with my ffmpeg settings? It always ends up just copying the audio over.

Basically I compressed the video stream to under 2gb, but the audio is still 2gb and i want to compress that to get under 4gb for a final file.

I am a moron, Flac cant be compressed with out converting it to a totally different codec. so truehd to flac to opus works fine. When I was doing truehd to opus it was garbage. flac being a middle man it works fine.

Weellll akshually FLAC is already compressed, it’s just lossless compression.

But yeah for a 5.1 file you’ll still end up with a considerable file size.

Although I’m pretty sure last time I did this I didn’t have to specify the channel_layout flag you did.