Always allow USB DAC bit perfect

[Jako Du Toit]

Hi,

I have been using BubbleUPnP for years and was excited to see that BubbleUPnP can now also play directly to my USB DAC, bypassing normal Android sound pipelines. My problem is that the DAC is also a headphone amp which has an external volume control (Chord Mojo 2). In this case BubbleUPnP does not want to enable bit perfect playback because the volume cannot be controlled via USB. The result is that my audio is resampled into a lossy format and software volume control is forced.

I would appreciate it if I can set the output to bit perfect, regardless of whether BubbleUPnP can adjust the hardware volume. Is this possible?

Regards, 

Jako

[Bubblesoft]

Hi,

For bit perfect to work, Android must report to the app that the USB DAC is bit perfect capable.

If the app reports that bit perfect is not supported for a DAC, then the system does not report that capability.

Although bit perfect reporting is supported since Android 14, I wonder if it might be different depending on Android version (14, 15, 16)

or if this capability is purely determined by the USB DAC.

For example, I have a Fosi DAC and an inexpensive USB-C->3.5mm jack converter and both are reported as bit perfect capable on 

my Pixel Pro 8 running Android 16. 

However, the default 'Use best sample rate / bit depth' mode is not that bad as it will set the DAC

to use the matching sample rate / bit depth of input audio (or the closed match if no exact match)

with the system's mixer  just modifying audio to apply volume.

[Lars Modig]

I bought the Moondrop Dawn Pro 2 and Bubble UPnP also tells me that it's not compatible with Bit perfect ? Running Android 15 on a Sony Xperia 5...  Can you trust that what Bubble UPnP shows as sample value is what the DAC receives or is Android messing around with it ? I guess it's not a deal breaker since I anyhow most likely cant hear any difference but of course I want it to be playing to it's full potential... 

/L

[Bubblesoft]

The USB DAC might be bit-perfect capable, but the audio sub-system of Android reports it is not, thus BubbleUPnP cannot play to it in bit-perfect mode. 

That is not super important anyways, as in normal USB mode, the app can send the audio to the DAC at the audio's native samplerate/bitdepth (for example

if you play a 192 kHz / 24-bit track, it will be sent to the DAC as such).

The only difference with bit-perfect is that in USB non bit-perfect mode, Android applies volume before sending the the PCM stream to the DAC.

In bit-perfect mode, volume must be changed on the DAC itself.