Read multi-channel audio in video files?

[vocalnick]

Hey all,

I'm using OBS to record some videos with multiple audio channels. Currently recording to MKV and then re-muxing to MP4. I'm wondering if there's any simple way to get them into Reaper for video/audio manipulation with the multi-audio intact?

They come into Premiere Pro OK with multiple audio channels, but dropping them into Reaper only seems to recognise the first stereo tracks. I've tried both the MKV and MP4 files and get the same behaviour in both. Item Properties only reports 2 audio channels.

Any thoughts?

[FixItInPost]

I read somewhere on the forum that REAPER cannot handle multi-stream/track audio, just multi channel audio, hence the "Channel Mode" option within the Media Item Properties window.

Read my post on this thread which explains (rather verbosely and possibly confusingly) the difference between channels and streams (a.k.a. tracks).

It would seem that OBS exports separate streams and that is why REAPER only reads the first stream.

If you're familiar with FFmpeg you could write a batch/bash file that takes the multi audio stream MKV files and exports separate audio files for each stream

[vocalnick]

Hey, thanks for the reply 🙂

That makes perfect sense. It would be lovely if Reaper could interpret the streams and treat them as channels, but I (more or less... sort of) understand that they are different things.

I’ll look into an FFMPEG solution if it comes up often, but I might just export WAVs from Premiere Pro in the meantime.

Thanks again!

[vocalnick]

Incase anybody comes across this later, I found an open-source program called MKVToolNIX which let me split out the separate audio tracks as MKA files.

I had some weird behaviour with the MKAs and Reaper (crashing and whatnot) but the Remux function in OBS let me change them to MP4, which Reaper handles with aplomb.

This is all done without any transcoding, so it was SUPER fast.

[EpicSounds]

I use FFmpeg Batch AV Converter to get audio tracks out of my obs recordings. I skip the OBS remux function.

[SonicAxiom]

in case you are interested: I just added new functionality to my AVConvert tool (see its thread here). You can now right-click a video file containing 2 stereo audio streams and merge-convert those into a 4-channel wave file.

.

[daniellumertz]

why is this a thing? Like why reaper don't get all tracks of some video files?

Just Found the answer https://forum.cockos.com/showpost.ph...77&postcount=2

@EpicSounds would you mind sharing your ffmpeg code or preset?

[EpicSounds]

Originally Posted by daniellumertz

why is this a thing? Like why reaper don't get all tracks of some video files?

Just Found the answer https://forum.cockos.com/showpost.ph...77&postcount=2

@EpicSounds would you mind sharing your ffmpeg code or preset?

on windows I switched to using SonicAxiom's AVConvert. It works well

[ashcat_lt]

But I’m going to ask again: Why, if you are the one doing the recording in OBS, are you recording to separate track/streams rather than recording multichannel audio which reaper handles just fine? It can be a little messy to set up initially if you’re not using the ASIO plugin, but it certainly can be done. I mean there’s like six active threads on this issue, and most of them at least the reason it even came up is because you recorded the video wrong to begin with.

Edit - but it would be nice if Reaper could just figure out how to access all the alternate track/streams natively.

[EpicSounds]

because I'd still have to split them out as separate files for post production regardless. the audio should always be separated from the video clips for performance reasons

[daniellumertz]

Originally Posted by ashcat_lt

But I’m going to ask again: Why, if you are the one doing the recording in OBS, are you recording to separate track/streams rather than recording multichannel audio which reaper handles just fine? It can be a little messy to set up initially if you’re not using the ASIO plugin, but it certainly can be done. I mean there’s like six active threads on this issue, and most of them at least the reason it even came up is because you recorded the video wrong to begin with.

Edit - but it would be nice if Reaper could just figure out how to access all the alternate track/streams natively.

So is possible to export as a multichannel from obs using the ASIO extension? Currently I can only export as multitrack.

Yeah I got what you are saying about performance especially in heavy files + lot of chops and stuff like remixes
In some cases where I have multiple files I alternate between the audio and video using this script I wrote https://forum.cockos.com/showthread.php?p=2413613

[ashcat_lt]

Originally Posted by EpicSounds

because I'd still have to split them out as separate files for post production regardless. the audio should always be separated from the video clips for performance reasons

Sure but you could just let Reaper explode the multichannel files rather than taking a whole other step in a whole other application. In many cases I think people could get away with just routing the various channels to their own Reaper tracks for mixing without really needing them as separate files.

If you are using the ASIO plugin as a source, you just right click it and go into its properties. Right there is a window to route each of the ASIO inputs to OBS channels. You’ll need to tell OBS to record a multichannel (2.1, 5.1, whatever) format, of course. If you are using desktop audio as one of your sources, you let that go through on channels 1/2 and route your ASIO inputs to other channels. If you’re trying to record several different “desktop type” sources to different channels, you might need something like VoiceMeeter or similar to force them to different channels on the way into OBS, or use ASIO4All for that part and then the ASIO plugin in OBS, or something.

[EpicSounds]

Originally Posted by ashcat_lt

Sure but you could just let Reaper explode the multichannel files rather than taking a whole other step in a whole other application. In many cases I think people could get away with just routing the various channels to their own Reaper tracks for mixing without really needing them as separate files.

on my mac its drag and drop to convert the files. It even tells me when it's done with a voice alert 'job done'.

Having the project laggy because I'm trying to get audio from a compressed file with multiple instances is going to slow down the project more than batch converting in advance.
Even with single video files a phone for example, reaper runs better with the audio in a separate file.
I could explode and then glue, and I'd have reaper locked up until completed.

[ashcat_lt]

Those are fair points, though I'm not sure I'd ever notice. My video projects are generally either so simple it wouldn't bother me or so complex I'd never be able to narrow it down to that as being the issue causing lag or whatever. Basically, I pretty much expect video playback to be wonky, anyway, so...