# How to close auto downmix of MasterChannelGroup effected by studio bank
**URL:** https://qa.fmod.com/t/how-to-close-auto-downmix-of-masterchannelgroup-effected-by-studio-bank/20199
**Category:** FMOD Engine
**Tags:** cpp
**Created:** [May 6, 2023, 6:40am UTC](https://qa.fmod.com/t/how-to-close-auto-downmix-of-masterchannelgroup-effected-by-studio-bank/20199 "2023-05-06T06:40:45Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@LittleGreen1](https://qa.fmod.com/u/LittleGreen1)
#### Post date: [May 6, 2023, 6:40am UTC](https://qa.fmod.com/t/how-to-close-auto-downmix-of-masterchannelgroup-effected-by-studio-bank/20199/1 "2023-05-06T06:40:46Z")
Hi. I have a requirement which used FMODCoreAPI and FMODStudioAPI:GlobalMasterGroup has 16 channels output.It works well when i just play one sound has 8 channels output.But once i load a bank which MasterGroupBus output mode is set as 5.1channels, my sound will downmix automaticly to 5.1 mode.
> FMOD::Studio::System::create(&system);
> system-\>getCoreSystem(&core\_system);
> core\_system-\>setSoftwareFormat(48000, FMOD\_SPEAKERMODE\_RAW, 16);
> system-\>initialize(1024, FMOD\_STUDIO\_INIT\_NORMAL, FMOD\_INIT\_PROFILE\_ENABLE | FMOD\_INIT\_PROFILE\_METER\_ALL, NULL);
> core\_system-\>createChannelGroup(“test”, &channelgroup);
> core\_system-\>createSound(“D:/project/FMod\_Test/Debug/8channelstest.wav”, FMOD\_LOOP\_NORMAL, NULL, &sound);
> core\_system-\>playSound(sound, channelgroup, false, &channel);
> system-\>update();
> till now works well:
>
> 
> FMOD::Studio::Bank \*bank;
> system-\>loadBankFile(“D:/project/FMod\_Test/Debug/wavebanks/Master.bank”, FMOD\_STUDIO\_LOAD\_BANK\_NORMAL, &bank);
> system-\>loadBankFile(“D:/project/FMod\_Test/Debug/wavebanks/Master.strings.bank”, FMOD\_STUDIO\_LOAD\_BANK\_NORMAL, &bank);
> system-\>update();
> auto downmix occurred:
>
> 
I tried many methods but it didn’t work.
by setMixMatrix():
> core\_system-\>getMasterChannelGroup(&mastergroup);
> float matrix[16][16] = { 0 };
> for (int i = 0; i \< 16; i++) matrix[i][i] = 1;
> mastergroup-\>setMixMatrix(matrix[0], 16, 16);
or add a dsp in MasterChannelgroup with readDSP callback:
> strcpy(dspdesc.name, “test\_dsp”);
> dspdesc.version = FMOD\_PLUGIN\_SDK\_VERSION;
> dspdesc.numinputbuffers = 16;
> dspdesc.numoutputbuffers = 16;
> dspdesc.read = readDSP;
> core\_system-\>createDSP(&dspdesc, &dsp);
> mastergroup-\>addDSP(1, dsp);
> FMOD\_RESULT F\_CALLBACK readDSP(FMOD\_DSP\_STATE \*dsp\_state, float \*inbuffer, float \*outbuffer, unsigned int length, int inchannels, int \*outchannels)
> {
> memcpy(outbuffer, inbuffer, length \* sizeof(float) \* inchannels);
> return FMOD\_OK;
> }
> still not working:
>
> 
I can reset studio MasterGroupBus output mode to make it work correctly, but is there any other way to config channel.
Thanks.
---
### Author:  [@Connor\_FMOD](https://qa.fmod.com/u/Connor_FMOD)
#### Post date: [May 10, 2023, 12:38am UTC](https://qa.fmod.com/t/how-to-close-auto-downmix-of-masterchannelgroup-effected-by-studio-bank/20199/2 "2023-05-10T00:38:43Z")
Hi,
Unfortunately, this isn’t currently supported in FMOD Studio. However, there is a task for this feature and I have noted your interest.
There was an alternative option posted in another forum here: [Automatic Downmix of multichannel streams. Bug? - #16 by mathew](https://qa.fmod.com/t/automatic-downmix-of-multichannel-streams-bug/18103/16) which may be a solution.
Hope this helps!
---
### Author:  [@LittleGreen1](https://qa.fmod.com/u/LittleGreen1)
#### Post date: [May 11, 2023, 9:47am UTC](https://qa.fmod.com/t/how-to-close-auto-downmix-of-masterchannelgroup-effected-by-studio-bank/20199/3 "2023-05-11T09:47:30Z")
Thanks.
As he mentioned, I used CoreAPI to solve problem.
It seems automaticly downmix occured when studio mastergroupbus speakermode were different from core masterchannelgroup’s.So when load banks and it changes the masterchannelgroup speakermode to 5.1, it indeed worked by set it back to FMOD\_SPEAKERMODE\_RAW.
However, it didn’t mention about this in WhitePaper or APIReference.So maybe it’s the only way to achieve this effect befor new feature actual installation.
---
### Author:  [@Connor\_FMOD](https://qa.fmod.com/u/Connor_FMOD)
#### Post date: [May 12, 2023, 5:03am UTC](https://qa.fmod.com/t/how-to-close-auto-downmix-of-masterchannelgroup-effected-by-studio-bank/20199/4 "2023-05-12T05:03:18Z")
I see, thank you for looking into this. I will make a note to add this to the documentation.