Automatic Downmix of multichannel streams. Bug?

I’m experiencing a frustrating bug in FMOD Studio 2.02.04 for Mac. It seems that any multichannel audio file that does not conform to pre-defined formats (stereo, 5.1, 7.1.2, etc is subject to automatic down mix to stereo, which is very frustrating when you want to create an event with a 14 channel file with 7 stereo pairs! if the stream has 12 channels (6 stereo pairs) it gets interpreted as a 7.1.4 format file, and all the channels are exposed in the channelMix DSP. To be functional as an interactive music tool, FMOD Studio needs to have the ability to have an event interpret input channels in a “raw” format for mixing and be able to choose a panner format for output, which is typically stereo. Without this necessary feature, the only way currently that I can see to control the volumes of stereo pairs in a multichannel file is to use the low-level Core API and control volumes via the channel matrix, which is certainly doable, but seems unnecessarily cumbersome.

I have not been able to reproduce the buggy behavior you describe. When I test here, the channel formats of audio files are preserved, and are only downmixed to stereo if they’re routed into a bus whose channel format is stereo, or if they’re routed through an effect that causes that kind of downmix.

If you check in the “build” tab of FMOD Studio’s preferences window, you’ll see a list of your project’s target platforms. If you select one of these platforms, you’ll see it’s surround speaker mode, which determines the format to which the signal will be downmixed by the master bus’s panner and any FMOD spatializer effects in your project. Is this mode set to stereo for any of your project platforms?

Thanks so much for the reply, Joseph.

If I change the project format to stereo, my options are even more limited. Here’s the flow:

14 channel AIFF file → Group channel → master

FMOD Studio’s channelMix DSP does not give access to the volumes of any of the 14 channels, as it is automatically down-mixed to the project’s channel config before there’s an opportunity to expose an of the channel volumes for a mix. This is a severe limitation, as ideally one should be able to parameterize mutes and channel volumes of each stereo pair in the 14 channel file. I know this feat can be accomplished using the low level API, but I can’t see any way to make it happen in FMOD Studio. Am I missing something?

Are you able to provide the 14 channel sample you are using? It should be possible to do what you are asking, but I’m not sure how it is mixing down before getting to the channel mix effect.

I could certainly send you the file in Ogg format, but I’ll need an email address for the weTransfer.

PS - just did a sanity check and yes, a 14 channel file gets automatically down mixed to stereo, as its not a recognized surround channel format set like 7.1.4, which would = 12 channel audio file.

I sent a 14 channel wide AIFF file to support@fmod.com via WeTransfer. Hope that does it!

Thank you for sending this through.

As you suspected, when FMOD Studio encounters an audio file that has a channel count exceeding its maximum number of channels (12) it will automatically downmix to stereo.

If you wish to work with a multi channel audio file such as this, it would be advised to use the FMOD Core API and use ChannelControl::setMixMatrix to route the 14 channels to stereo output (or your desired output) and then manipulate the individual channel volumes as needed.

https://www.fmod.com/resources/documentation-api?version=2.02&page=core-api-channelcontrol.html#channelcontrol_setmixmatrix

Thanks for confirming what I thought. However, even if a file has 12 channels (7.1.4), it would still be useful for developers to be able to override the surround defaults in FMOD Studio and establish individual channel control via the GUI. The low-level API is a solution to be sure, but adding this feature to Studio would certainly simplify things. FMOD is a wonderful tool that keeps getting better, and this would make it even better! Thank you.

So the official feature request would be: “Can we have the ability to insert a channel mixer at the tail end of an instrument?” :slight_smile:

This definitely sounds like a good idea. I have raised a feature request to unlock the channel count of tracks and the channel mix effect in our tracker.

We’re trying to do some sku planning here, and we’re wondering when this feature “override automatic downmix and insert a channel mixer for multichannel sounds” might be released. It seems like a relatively trivial enhancement to FMOD studio, but it would mean the world to my company, as it opens the door to a whole world of interactive music and ambience. This needs to be part of Studio ASAP. The other alternative would be to write a DLL compiled for every target platform, and while possible, is far more cumbersome from a development perspective. Please give us an ETA! :slight_smile:

We are looking at including this as a part of the next major version (2.03). It is a bit intricate for a minor release as it would see compatibility issues with older minor versions. Unfortunately we can’t give a very accurate ETA on when the next major release is.

Thanks so much for the update on this. So glad you’re going to include this feature! Without giving anything away, I know you guys shoot for a minor release every month, but how often on average does a major release happen? Also, I would be happy to volunteer as a beta tester.

Unfortunately we don’t have a very accurate estimate for when the next major release would be, but you can sign up to our newsletter to get notified when it is released.

We currently don’t have a beta testing program but all major versions are released in an early access capacity.