USB Audio (DAC) support, digital outputs

rille

In the changelog I found:

Changelog 240424:
Added USB Audio support in Settings

It was also stated that the support is experimental. Is it still experimental? What can be set in settings? Also the sample rate (like the newer Joying head units)? Is the DSP completely bypassed?

Does anybody use USB Audio and can share the experiences? It's mandatory for me that it works without problems.

How are the digital outputs working? Is the signal routed through the DSP? I guess volume control is still in effect? But what about the rest of the DSP (EQ etc.)? Which sample rate is used for the output? 48 kHz or higher?

dudu-langzi

rille The current digital output is a 48 kHz sample rate. However, it will be increased to 96khz later.

rille

I have a DUDU7 now and will give some information in case somebody else has the same questions.

The TOSLINK output uses 48 kHz sample rate. The output signal is not at full level. With volume at 36 and SPDIF passthrough activated it looks like this:

I used a 0 dB 1 kHz sine signal. I would except that pass-through is really pass-through. The EQ is bypassed but volume control (Balance sound + Main volume) is still in effect.

If I change the setting in "Balance Sound" from 5 to 10 the signal is still not at full level:

USB-Audio works without problems. 96 kHz sample rate is used and the signal is at full level:

So if you want a perfect signal use USB DAC. Of course there will be resampling to 96 kHz.

Gagamel

rille In your experience there is no way to get the full digital signal level using S/PDIF?

rille

Gagamel
Only with USB DAC.

HawkStar

Hi - which USB port is used to output USB Audio?

rille

HawkStar
You can use any USB-Port.

jacob

rille is type C port is possible ? thank you

rille

jacob
What do you mean?

It has a USB-C port. It's USB 3 (AFAIK 5 Gbps) and it also supports video output.

jacob

rille sorry my question seem not clear enough , i mean type c port also support usb audio right ?

rille

You can use also the USB-C port for your DAC. But it makes no sense. USB 2.0 is fast enough for audio .

jacob

rille thank you, about usb audio , after did some testing with my DAC, i noted that dudu Os convert ( upsample, resample or whatever.. im not sure ) all bitrate to fixed 96khz, It's not bitpecfect

surfer63

Don't make the mistake to confuse a USB-C adapter port, or a USB-A or micro-USB with the USB protocol that is running over it. There is a difference between the adapter and the protocol.
The protocol USB 3.1x or USB 3.2x runs on USB-A, USB-B and usb-C adapters depending on the USB chip behind it.
And as the USB-C adapter becomes to then standard for chargers worldwide (also for stupid Apple), it might indeed be that newer, faster USB protocols will only run on the USB-C adapter.

rille

jacob I wrote that in the second post: "Of course there will be resampling to 96 kHz.". And even if you would have bitperfect output (like UAPP has) the DSP will resample. Most DSPs use 96 kHz so choosing 96 kHz for USB DAC was a good decision.

jacob

rille yes UAPP can do bitpefect , but there is a problem that when use Uapp with dac, it take control audio level . So other apps can not sound out a music anymore evenly i quit UAPP. Have to reset headunit or plug out usb cable from DAC to make it sound again. This is not too convenience for now, hopefully Dev will improve it in the near feature

jacob

dudu-langzi its not about sample rate , its about resample process. Could it support an option that can purely using sample rate of the song i play, only apply for music app. I dont mind if i can not use radio, phone call, navigation sound…etc

rille

dudu-langzi
At digital output it's 48 kHz. But with USB DAC it's 96 kHz. Did I write anything different? I guess you didn't read the posts carefully...

jacob
If you want this use UAPP. You have to set the option: System->"Release USB audio driver on Home". This worked for me well. But the question is: which device do you have behind the USB DAC? Normally it's an DSP and the DSP will resample to it's internal sample rate. And I wouldn't overrate the bit-perfect output, especially in a car.

jacob

rille i did tried to use option "release USB audio driver on Home" but that's strange it not working. I will try again. I do connect DAC to my brax dsp used on car . Resample by android is not really good process, i did test and notice it very difference in a bad way

dudu-langzi

rille The current usbdac is in global mode. It definitely needs to be resampled, like you said.uappExclusive mode does what you say, but that results in no sound at all except for the player.

Mish82

Hi, I have been trying to output audio from my Dudu 7 with USB,

I have been using toslink (optical) to output audio up until now and still have the toslink cable plugged into the back of the unit. But I would like to output with USB.

I have set the USB Audio Output (beta ) function on and still can not output audio via USB.

I have also tried by connecting into the USB C port on the back of the unit and also have tried connecting to one of the 3 USB connections that go into the back of the unit also.

I can't seem to be getting any audio output out of the unit.

Is there anything I am missing to make it work?