TOPIC:

Hi!

For my research project concerning beamforming, I have recently acquired a UMA-16 unit.

However, despite having read the user manual as well as the datasheet, some questions remain :

• What is the order of the audio channels, relatively to the placement of the microphones? The numbering is quite strange on the PCB, and I couldn't precisely determine the channels' order from recording... EDIT: I just discovered that the channels actually follow the numbering on the PCB. I find it a bit odd, is there a reason for such a weird order?
• Why is the sample frequency so high considering that, with a spacing of 42mm between the microphones, the spatial aliasing frequency is 3kHz?
• I have seen several posts in the forum with screen captures of a configuration software, allowing for on-board beamforming with configurable steering angle. Is there a similar plug-in for the UMA-16 and if so where could I download it? If not, what is the point of having such a powerful DSP architecture on board if it's only taking care of audio conversion?
• Finally, my project also involves video processing, and the camera slot on UMA-16 was yet another reason why it was suitted to my project. However, I couldn't find a camera with the same format as the slot. On the picture attached to my post, you can see a such a camera attahced. Do you have a reference and/or a link to this product, or an equivalent one?

Thanks a lot in advance!

Florent

@ Florent

Few comments to see how we can help.
a) Order of MEMS is on the PCB indeed. It was done as such for layout reasons... But i guess that if you don't like it, simply just build another PCB I guess to have another layout?
b) Sample rate is up to you. You can always use another sample rate I guess to fit any of your needs It supports from 8k~48k.
c) That control is for the DSP mode of the UMA8. The UMA16 as per manual doesn't have such beamforming library embedded. The SHARC DSP is used for the high performance PDM to PCM conversion mainly.
d) The camera we used is the following: wholesaler.alibaba.com/product-detail/Fa...UVC_60691042268.html
We'll soon put it online in our shopping cart as an add on. Feel free to contact us if you want a sample (Support - > CONTACT US)

DevTeam

Hey!

Thanks for your prompt answer.

The mic order isn't really a problem, I was just wondering if there was a specific reason considering Matlab's phased array library as well as other beamforming APIs use a top to bottom, left to right indexing. The audioDeviceReader method of Matlab's DSP library allow for custom channel mapping, so no problem there.

For the sample rate, how can I change it? Couldn't find the option on the configuration software. maybe I missed it!

I'm still struggling a bit to make a simple beamforming test on Matlab (the level of the mics is quite quiet there and the beamforming function just doesn't give good results) but as soon as I make it work, I can share my code if you'd like to add it to the wiki.

Thanks for the camera, I'd be indeed interested in a sample, I'll tell my research tutor about it.

Cheers,
Florent


EDIT: Just fixed my code, I have a Frost beamforming example working in Matlab if you're interested

Hi Florent

Thanks for the update and exciting to hear of your progress!
a) You're right that we didn't consider the way Matlab lib would label.. We should have paid attention to it. It's a simple remapping as you correctly suggested. Thanks for
b) Sample rate / You can fix it under ASIO setting of the devicereader object if I recall no? (www.minidsp.com/applications/usb-mic-array/uma-8-16-matlab). ASIO controls the sample rate when the software takes control over it.
c) Camera / Sure. Do get in touch with us (support.minidsp.com). We'd be happy to help!
d) Super exciting to hear of the Frost Beamforming example. I'm sure that other community members would love to have some info here.
Maybe we could add it to the UMA16 app note?

DevTeam

Hey!

Yeah, I got the sample rate solution after posting, should have made an edit. Sorry about that!

For the camera my research tutor actually already ordered it through the university's retailer. Thanks a lot for the link!

I've attached the (commented) Matlab code for those interested. I changed the Frost beamformer to a LCMV beamformer because it performs better in my case. It's a bit sloppy and needs more work but it's a functional basis.
I can also provide a simulation code for the UMA-16, which might be easier to showcase (you can just hear the result even if you don't have the array).

Cheers,
Florent

EDIT: one more question : the distance between the camera's holes (the 4 M3 holes in the center of the array) isn't specified in the mechanical drawing of the datasheet. I don't have the drawing for the camera yet, and it would really help me if you could tell me the distance between 2 screws (I'm measuring somewhere around 20mm but I don't have a precise tool)

Hi Florent

Great progress indeed and thanks a ton for sharing your project with the community!
Is that Ok if we share your great sample on the UMA16 Matlab app note page (www.minidsp.com/applications/usb-mic-array/uma-8-16-matlab) for the purpose of other community members?

In answer to your question, the distance is 23.5mm (hole to hole). We've added a CAD drawing to the UMA16 page.
BTW, we've added the CAD to the product page (can open with free cad viewer to investigate the size).

Look forward to your updates with the camera.

DevTeam

devteam wrote:

Is that Ok if we share your great sample on the UMA16 Matlab app note page (www.minidsp.com/applications/usb-mic-array/uma-8-16-matlab) for the purpose of other community members?

Yeah of course, no problem!

devteam wrote:

In answer to your question, the distance is 23.5mm (hole to hole). We've added a CAD drawing to the UMA16 page.
BTW, we've added the CAD to the product page (can open with free cad viewer to investigate the size).

Thank you for that, it will turn out very useful.

Hi, for Matlab, we can use function 'audioDeviceReader' to get the audio sample? but how to do that with C++ on Windows? any demo? is it possible that use APIs in library 'winmm.lib' to do that? for example, the APIs listed below:
(1) waveInOpen
(2) waveInStart
(3) waveInAddBuffer
...

Best Regards,
Junchao Cai

Dear Flo96, thank you for your code. It really helped me to understand some working principles of the UMA-8.
Do you have an example for a circular microphone array?

Cheers!