Mix/EQ audio on the way in?

[Tonefinder]

I am transferring from old, analog tape sources using Elgato Video Capture hardware.

From the point that newly-digitized audio reaches my PC, I would like to rout it through a DAW (Reaper), where EQ plugins will be applied, then have this effected audio be what is captured in OBS, along with the untouched video feed. I have a multi-channel audio interface (RME 802), which I already see is recognized by OBS.

Is this possible?

Thanks,
Lance

 

[AaronD]

What you need is called a loopback. Install one, and you'll have both a virtual speaker and a virtual mic. Whatever you send to that "speaker" will show up in that "mic". Connect the apps accordingly.

A popular one is called "Virtual Audio Cable", but it's not the only one available. Now that you know what to google, have fun!

You might need to adjust the sync delay in OBS, to account for the audio path being longer. Record some, load the recording into a video editor, separate the video and audio into separate tracks, and play with the alignment until it feels best. Then translate that into a delay in OBS and record another test.

 

[Tonefinder]

Thanks for the reply! Do you think the loopback feature in my audio interface would work?

 

[AaronD]

Normally I'd say no, because it "faces the wrong direction". Most audio interfaces are just fancy sound cards and no more. That's usually all you need anyway, but don't expect it to do any more. The sound card might have a switch to send its inputs directly to its outputs, without the computer seeing anything different. That's a loopback for the physical connections, but you need one for the computer.

But since I googled yours and saw that it (possibly?) has some DSP built into the interface, as a hardware digital mixer in a 1U rack space with USB control, the answer changes to "maybe". It's also possible that the DSP function is done on the PC side, with the interface still being just a sound card, in which case the answer is still "no".

Having seen the array of I/O that you have, I also want to suggest a physical patch cord from some spare outputs to spare inputs, and use that as the loopback that you need. But that won't work either because OBS takes all 30 channels of that device and mixes them together before it lets you touch it. I found that out with an 18-channel XR18 and a 32-channel X32, both from Behringer.
You might get a dedicated sound card to do that with, as a physical loopback that "faces the right direction", but it'd be better at that point to install the virtual one.

 

[Tonefinder]

Wow, thank you for such thoughtful, detailed advice!

I have installed Virtual Audio Cable, but am not sure how to perform the routing. And actually, I don't really understand the signal path, either. I have analog audio originating from a VCR, running through my Elgato Video Capture device, then into the computer.

I need to get the audio into my DAW for processing and from there, into OBS for capture. I'm not sure where in this process the Virtual Audio Cable is involved, or how (the Youtube videos I've found do not address this type of application).

It's a lot to ask for a detailed explanation of how to do this, but if you're up for it, that's what's needed!

 

[AaronD]

Think of the DAW as a live audio console. It has live inputs and live outputs, whatever processing you need, and no memory except for settings. OBS is a separate recorder that "plugs into it".

1. Forget OBS for the moment, and get the audio into the DAW. Use its support for that.
2. Send the DAW's output to the virtual speaker. Use its support for that too.
3. Remove all of OBS's audio sources, and connect one of its 4 global mics (Settings -> Audio) to the virtual mic.

---

Since there's video involved too, you might need to adjust the Sync Delay between audio and video. Record some, load it into your favorite video editor, separate the audio and video into different tracks, and play with the alignment until it lines up correctly. Then take the difference that you ended up with, and translate it to this setting:

You should only have one entry there, since all of yours comes from the DAW, and you might need to uncheck "Active Sources Only" to see it.

 

[koala]

Since you want to optimize the audio from an old VHS recording and not create a live stream, I recommend you create your recording with no audio processing at all. Record directly what OBS is getting from the capture device with no filters. Use a high audio bitrate such as 320 kbit/s.

Optimize audio in a post processing step with an app specialized for audio. Not OBS.

This way you can tinker with the settings and process audio over and over again until you satisfied without the need to record from tape again. Then replace the raw audio track in the video with the post processed audio.

 

[AaronD]

Optimize audio in a post processing step with an app specialized for audio. Not OBS.

The OP already is. It's just pre-processing here, instead of post. Capture -> DAW (processing) -> OBS (unchanged)

This way you can tinker with the settings and process audio over and over again until you satisfied without the need to record from tape again. Then replace the raw audio track in the video with the post processed audio.

Yes, generally that is the way to do it. Record dead-raw, and do all the processing later so that you don't get stuck with some processing that you don't like. But the OP asked about pre-processing, and it's good to have (another?) explanation of the concept for others to find.

Also yes on the high bitrate, except that 320kbps is still compressed, and the codec is lossy. Uncompressed stereo 16-bit 44.1kHz is 1411.2kbps. Probably not noticeable, but still...

Since it's only 640x480p30 or thereabouts (no point in going any higher for VHS or DVD), maybe it becomes reasonable to use the lossless / huge file option in OBS's Simple Mode? That would also give you the opportunity to tweak the video later, without generational loss, not just audio.

With all of that said though, it's also nice to be able to just play the tape and have a finished capture with all the required tweaks already done. That might be what the OP is going for. Figure out what the settings need to be, then just run a bunch through.