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Old 01-23-2009, 03:15 AM   #1
nicholas
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Default Multiple Channel Audio Format Question

I'm trying to prepare something for the next User Guide to illustrate and explain the new multi channel audio format stuff. Got a quick question, to see if I'm on the the right track. Never worked with multiple channel audio formats myself.

As an example, suppose you were preparing for 5.1 format. Would you then reserve on your tracks channels 1 to 6 for dividing tracks according to how you want to distribute them between speakers, and use other channels(e.g perhaps 7 and 8 for stuff like ducking, then render the final mix to 6 channel wave format?

Or am I missing the mark?

Any help, comments etc would be much appreciated.

Thanks!
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Old 01-23-2009, 03:48 AM   #2
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TV 5.1 Mixes are actually rarely layed back to tape from a DAW. That's the job of Dolby-E capable facilities or folks who encode that stuff. Details of that interesting procedure can be obtained on the Dolby site.

The basis for all this will mostly be single channel files, and in some cases six channel WAV or AIFF files.

Dolby Digital encoders take a variety of formats, and single channel files are the most safe option. The reason for this is that there is more than one way to lay out the channels in a 5.1 mix. To avoid confusion and (costly) mistakes, single channel files are chosen. You can't go wrong with those, unless you're very careless.

Left, Right, Center, LeftSurround, RightSurround and Low Frequency Effect are the channels. There are combinations like LCRLsRsLfe, LRCLfeLsRs and so on. So multichannel are problematic in that encoders may assume a specific layout but the person having generated the multichannel WAV file actually chose another layout entirely. Multichannel files can become very large as well. Stems are kept as 24-bit/48khz PCM files, or in some cases even 64-bit float files(Harrison does this).

Traditionally Protools has always been a single-channel file DAW, and this is one of the occasions where this is an advantage. Reaper so far has managed to sidestep the use of such multi-mono files through complete absence of usable functions to group such files in to one item. This feat is achieved in Protools by selecting the items and dragging them on a surround audio track. At some point a viable solution is needed for Reaper, preferably one that requires no programming and complex macros by the user.

The file extensions of the single channel files for a multichannel mix(5.1, 3.1, 2.1 or any other) are

filename.L.wav
filename.R.wav
filename.C.wav
filename.LFE.wav
filename.Ls.wav
filename.Rs.wav

That's the norm for broadcast WAV files. On the Mac AIFF file names usually have no *.AIF ending.

How easy or how hard this is to do in Reaper will be part of how successful Reaper can be in this regard. This is the big league of professional audio where the tolerance for mistakes isn't really there.
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Old 01-23-2009, 05:15 AM   #3
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Thanks for all that. That certainly fills in one or two pieces of the puzzle for me, and explains 5.1 perfectly.

To return to the general issue of multi-channel audio file formats though, I can now see that you wouldn't use this for 5.1.

So, leaving 5.1 aside, if you were rendering to multi-channel format file (say 8 channel) would I still be right in assuming that for your tracks you'd reserve channels 1 thru 8 for this, using other channels (e.g. 9 and 10) for things like ducking?

Thanks for any help here ...
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Old 01-23-2009, 06:09 AM   #4
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You refer to what is called 'channel congestion' in chapter 11.12 of your guide?

Reading that, I have another question. You`re speaking about sidechaining and parallel FX in your examples, here I could (with some management overhead) avoid using channels 1-8, but I cannot with multichannel vsti.
So my question is:

Would that 'channel congestion' also refer to sends I create in order to set up multichannel vsti's?
With these I would be pinned to using for example sends on channels 3/4 to get the audio of the second stereo channel of that vsti. How will that fit with creating multichannel audio files by rendering the master? Will the second stereo output of that vsti be inavoidably output on channel 3/4 of the master track and also in the rendered multichannel file?
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Old 01-23-2009, 07:00 AM   #5
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Nicholas, it might be simpler than you think ... two possible applications for multitrack renders might be packaging stems, or packaging multiple versions of the same source (for example I think BFD's drum samples are 12-channel wavs, with the same sample recorded via a different mic in each channel).

Say you had the world's simplest stem mix of a mono vocal track, mono guitar track, and a stereo room track. You could set up 4 channels on the master, send the mono tracks to master channels 1&2, and the stereo track to master channels 3&4, then render all four channels. You don't need to do anything different in your project setup (reserving channels for different purposes or what not), just set up the master sends how you want for a multichannel render.
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Old 01-23-2009, 01:08 PM   #6
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Quote:
Originally Posted by gofer View Post
You refer to what is called 'channel congestion' in chapter 11.12 of your guide?

Reading that, I have another question. You`re speaking about sidechaining and parallel FX in your examples, here I could (with some management overhead) avoid using channels 1-8, but I cannot with multichannel vsti.
So my question is:

Would that 'channel congestion' also refer to sends I create in order to set up multichannel vsti's?
With these I would be pinned to using for example sends on channels 3/4 to get the audio of the second stereo channel of that vsti. How will that fit with creating multichannel audio files by rendering the master? Will the second stereo output of that vsti be inavoidably output on channel 3/4 of the master track and also in the rendered multichannel file?
gofer -

Yes, that was written for Reaper 2.5 remember BEFORE multichannel audio formats existed in Reaper. I think you are right (but see my next post).
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Old 01-23-2009, 01:12 PM   #7
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Quote:
Originally Posted by schwa View Post
Nicholas, it might be simpler than you think ... two possible applications for multitrack renders might be packaging stems, or packaging multiple versions of the same source (for example I think BFD's drum samples are 12-channel wavs, with the same sample recorded via a different mic in each channel).

Say you had the world's simplest stem mix of a mono vocal track, mono guitar track, and a stereo room track. You could set up 4 channels on the master, send the mono tracks to master channels 1&2, and the stereo track to master channels 3&4, then render all four channels. You don't need to do anything different in your project setup (reserving channels for different purposes or what not), just set up the master sends how you want for a multichannel render.
Thank you, that is a big help .. so to relate this back to my previous question.

If in this project I was also using the vocal to sidechain control a compressor on the guitar track, presumably I would not be able to use 3/4 for the sidechaining, or the vocal would be added to the room track when rendered. Instead I would need to use, say, 5/6 as the aux input on the guitar compressor?

Thanks ... we'll get there!
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Old 01-23-2009, 02:10 PM   #8
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Quote:
Originally Posted by schwa View Post
Nicholas, it might be simpler than you think ... two possible applications for multitrack renders might be packaging stems, or packaging multiple versions of the same source (for example I think BFD's drum samples are 12-channel wavs, with the same sample recorded via a different mic in each channel).

Say you had the world's simplest stem mix of a mono vocal track, mono guitar track, and a stereo room track. You could set up 4 channels on the master, send the mono tracks to master channels 1&2, and the stereo track to master channels 3&4, then render all four channels. You don't need to do anything different in your project setup (reserving channels for different purposes or what not), just set up the master sends how you want for a multichannel render.
At some point, Reaper will need to support naming shemes for rendering multichannel outputs of tracks. I'll confess I haven't tested what the new 3alpha1 can do in this regard beyond dropping a couple of multichannel files in there, but I figured you were going to work on this for a while yet before its use is streamlined and intuitive enough.

This suggests rendering presets, based on the number of rendered channels of the track. Since I reckon you're going to keep the current options that include rendering each selected tracks output, the actual GUI will need to adapt as well. It's quite funny that Cubase SX 5 seems bring an interesting idea to the table as detailed in the preview video "In the fast lane". They also brought in the automation panel of Nuendo by the way.

Here's a shot from the video


This is quite a task, and 5.1 mixes are only a subset of what can be done.

Nicholas, to answer your question, yes, there are mixes that use eight channels simply because 8-channel digital tapes (DA-88 decks and its isotopes) allowed us to. The Dolby mod(MagnetoOpticalDisk) produced for each theatrical mix by a Dolby consultant contains something like that too.

The first six channels are taken by the 5.1 mix. The final two channels are usualy the LtRt, which is the optical Dolby Stereo mixdown. That's the fallback track in case all the other stuff on the film material fails to be read correctly. It's the classic optical print of a two channel audio, decoded in to 3.1 by a Dolby processor.

Dolby-E gives you eight channels on a 20-bit-audio four-channel capable deck. These are used in a similar fashion, though some clients want stuff like stems on there and a stereo mix, if there's no 5.1 requirement, which is pretty rare from what colleges in the states tell me.

So for effective playouts using Reaper(once an automatable well featured surround panner comes in to play), the current method may already work, if you're ok with bouncing out to stereo pairs or mono outputs, which requires the mono switch in the render dialog however. Minimizing the traps anyone can fall in to will help.

Btw, folks who now begin quoting 7.1 mixes, don't. Nobody(in any significant numbers) has the equipment to play them yet and SDDS is dead.
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Old 01-26-2009, 06:07 PM   #9
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Airon,

Thank you very much for this detailed and clear explanation.

My feeling is that (to be honest) while Reaper is capable of mixing to (say) 5.1, I couldn't really put my hand on my heart and recommend it for this - it is so much easier to do in other products.

Would you (or anybody else) agree/disagree with this?

My inclination is to make passing mention of it with an overview explanation in the documentation, but not go into detail at this stage - maybe if this feature gets a bit more user friendly in the future ....

Yes? No?
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Old 01-27-2009, 12:27 AM   #10
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Mixing for more than two channels in Reaper is a hack at the moment, so it's not recommended that you use Reaper for this purpose.

Just because you can do it, doesn't make it a good idea, let's put it that way.

The alternatives are Logic (200+ Euros, lousy audio editing), Nuendo (1750 Euros), Cubase 5 (600 Euros, has Nuendo4 automation now), Protools HD($10000+), Protools LE CPT($2000+) and the various specialized workstation systems whose price range is closer to consoles for this kind of work.

Plenty of alternatives for mixing, but we want to work in Reaper now, don't we.

They'll figure it out. Until then, the answer to the question of using Reaper as a multichannel mixing environment can only be no.
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Old 03-19-2009, 08:36 AM   #11
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Default Support B-format - ambisonic .amb

Can you support .amb files ?

Here is a description on how reaper is used as part of creating B-Format 4 channel ambisonic surround .amb files!
Is it possible to add support for all of the .amb file creation in reaper?

http://uod-true-multi-channel-mixing...nic+Wave+Files

Is it possible to add faciclity to record to a file with 4 channel tracks instead of just stereo?

In live recording of Ambisonics with a Tetraeder microphone I need a convinient way of handling 4 channel files that have to stay in sync and have the same gain.
It would be great get the 4 channel track format to support recording on all 4 channels.

Ambisonic B-format (storage format) is a First order format for surround sound XYZW files.

With a VST plugin you can decode to surround sound including height if you have setup of speakers that the decoder knows about.


Best Regards
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Old 03-19-2009, 10:07 AM   #12
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You should be able to record a multichannel file with 3 tracks in Reaper 3 alpha by bringing channels 1+2 in on track 1, bringing channels 3+4 on track 2, set track 1 and track 2 to route to track 3 discretely (4 channels of audio). Then set track 1 and 2 to input monitor only and set track 3 to "record output (multichannel).

Out of curiosity which tetrahedral mic are you using? I've often thought of getting one.
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Old 03-20-2009, 12:44 AM   #13
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Thank you for the tip on how to do a workaround,
But I do not really understand why it is neccessary :-).

I have this microphone
http://www.core-sound.com/default.php
I am using it with a E-MU 1616,
+ 4 channel mic preamp enabling me to use 4 of the line level inputs of the 1616.

For a good result the input gain have to be equal within 0.1 dB.

- B
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Old 03-20-2009, 03:13 AM   #14
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I can add another way here.

Record to four tracks, mono each. Route their outputs to one track that has four channels. Place your decoder VST there for listening. Bypass for rendering. The v3alphas can render multichannel WAV files, so depending on the channel configuration you need you can determine the routing yourself.

For editing, simply group the four recordings. Editing will stay completely on the money that way.

Btw, rendering dry, unity gain mono tracks with a pan law of 0 dB will give you carbon copies of your recordings in the resulting rendered file.

Hope that helps until Reaper can record more than two channels on a track.
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Old 04-16-2009, 07:27 AM   #15
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Hi My two pennies worth...

I have been playing with R3 Beta 3.

I set up the master with 6 channels, I add two new hardware outputs for my Centre, LFE, LS & Rs outputs and direct channels 3 - 6 to these outputs, I add a Surmeter 7.1 from AcousModules for 8 channel Surround master metering.

I add new track and give it six channels, I add a Spatpod 5.1 from AcousModules for 5.1 surround panning, I also add a Surmeter 7.1 on the track if I want to meter individual track levels.

Also on the track in Spatpod 5.1 I can select the Parameters to go on the track control which now show up as adjustable knobs to set up, for instance, LFE volume and Centre bias. See screenshot..

I can now Pan a mono or stereo track in 5.1 Surround. I can also do read/write automation on the parameters :-) see screenshot. I can also monitor in full 5.1 through my MOTU 828.

When I render the file to a .wav I specify 6 channels in the render dialogue and I get a 6 channel BWF wave file dialogue... see screenshot.

I know it's not brilliant but for specific 5.1 surround work I do, I think it meets most of my requirements. for mixing sound for games.

I know I can also render the files to separate wave files but the point here is the basic setup for doing the panning etc is fairly straightforward.

I know that many others who actually know what they are talking about will see many issues with this ;-) and I know that the AcousModules are not the leading edge. But for me it sort of works. I leave the actual encoding to Dolby to others who are happy to take my 6 channel .wav files.

Also if I add a new 6 channel track and import the 6 channel wave back it works fine with the six channels in the one track, and if I put an AcousModules 6 channel Miniroute plugin onto the track I can then re mix each of the individual channels, again with an SurMeter 7.1 if required for metering on the track.

For a Beta release this has been very stable for me.

Thoughts as always welcome.

BR Malcolm
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Old 04-16-2009, 08:25 AM   #16
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Nice work. FOr anyone wanting to do this themselves and haven't spotted the name of the plugin producer and the fact that they're free, go here:

http://acousmodules.free.fr/
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Old 04-16-2009, 08:38 AM   #17
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Nicholas,

If this is what your referring to in the changelog...

+ Multichannel (greater than stereo) media support, including MOGG

drop this file (.mogg) in the beta and you'll see what it does.
.mogg is like a "zip" file so to speak of OGG files (without further compression AFAIK). Only audio tho' no settings or plugs or anything like that.

Kinda like dropping a multi-channel MIDI file in and you get the dialog (IRCC) "spread channels across multiple tracks? (or something like that.)
It's another way to transfer projects or stems between various apps, rendered to a certain format like OGG or I believe wavpak.

http://www.adrive.com/public/43db0c9...eb338217d.html

(oops....heads up it's 21.5MB)

I don't think it necessarily needs more than a worthy mention like in an additional fuctionality section or something to that affect.
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Old 04-16-2009, 03:07 PM   #18
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Thanks fellahs, I'll check all this out.
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Old 04-17-2009, 08:44 AM   #19
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Good to see some development on the multichannel front.

Quote:
Originally Posted by nicholas View Post
[...]
To return to the general issue of multi-channel audio file formats though, I can now see that you wouldn't use this for 5.1.

So, leaving 5.1 aside, if you were rendering to multi-channel format file (say 8 channel) would I still be right in assuming that for your tracks you'd reserve channels 1 thru 8 for this, using other channels (e.g. 9 and 10) for things like ducking?

Thanks for any help here ...
I /would/ (also) use 5.1 audio with multi-channel files. When editing (cutting, looping etc.) I don't want to keep checking for sync between the files. It keeps my file folders less messy too.
Also, I sometimes record 5.1 stuff into a stereo file for L/R, and put the rest in either 4 mono files, 2 mono and one stereo for Ls/Rs, or 1 4 channel file. That way I can just use the L/R for stereo purposes (of course that doesn't work well in a lot of situations where it needs a proper downmix, but in some cases it's just fine like that).

Flexibility is good, but some standardization can be too. Often I personally don't care about encoding issues, I just want to compose / design everything in surround, and play stuff (instruments, fx, prerecorded audio) live in surround. I'd be willing to go quite some way sacrificing flexibility here in order to have a more usable workflow to do 5.1 stuff in Reaper. Using a certain file format or naming convention, sure, no problem.

To answer your question about reserving other channels for fx (things like ducking): I tend to use the same number of channels for fx on 5.1 stuff. I.e., all fx are in 5.1 too. So for example, I would use 6 channels for 5.1 audio, then the next 6 for sidechain fx (not just 2).

Maybe we should think about dedicated 5.1 type audio tracks, so by default all sends etc are 5.1 too, and it can have dedicated 5.1 panning GUI and automation parameters.
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