This is something that I've really wanted for a long time over a lot of different services. It would require support on a few levels (streaming software, the streamers themselves, and Twitch of course), but many video codecs already support it. One drawback would be the extra bandwidth it would take (or extra processing on Twitch's end if they decided to mix them together for each user). A potential strategy to avoid that issue is having one or a handful of default balances which Twitch would mix for you (eg. only talking or 50-50), and then an option to have a custom balance which would be processed client-side. Another thing that would be good is a third track for game audio, or (even better) an arbitrary number of tracks chosen by the streamer. I personally spend more time on Youtube than Twitch, but it would be great to see at least one service offering this feature (and maybe it would even become standard).
This is something that I've really wanted for a long time over a lot of different services. It would require support on a few levels (streaming software, the streamers themselves, and Twitch of course), but many video codecs already support it. One drawback would be the extra bandwidth it would take (or extra processing on Twitch's end if they decided to mix them together for each user). A potential strategy to avoid that issue is having one or a handful of default balances which Twitch would mix for you (eg. only talking or 50-50), and then an option to have a custom balance which would be processed client-side. Another thing that would be good is a third track for game audio, or (even better) an arbitrary number of tracks chosen by the streamer. I personally spend more time on Youtube than Twitch, but it would be great to see at least one service offering this feature (and maybe it would even become standard).