Check bit perfect output


I installed the latest version of Volumio 2 (2.041) on my Raspberry PI 3 and after having had some difficulties in the output configuration to the USB DAC of my Burson Conductor and manual installation of wi-fi dongle Edimax, now it all works :slight_smile:

Now I would like to verify that the output stream from the Rasperry PI usb to the USB of my DAC is bit perfect, that is, whether the audio stream is truly intact (e.g. input file 24 bit 96 kHz => output 24 bit 96 kHz).

There is this feature in the interface of Volumio, as in the “Playback” screen, or through some shell command during playback?



Well, it’s certainly possible, though not with a standard Volumio install. If you want to go all the way (whole system check), specifically for your setup, you’d have to capture the outgoing raw USB data stream with something like wireshark and from that recreate the actual audio data stream. Then, do a compare with the original data and you have your answer.

Not in any way a “Check Bitperfect” – “OK” button solution, but hey, it’ll be a challenge :slight_smile:

A lot of information to start with can be found in the /proc/asound directories.

See for more information.

You need to verify first that everything software related is set correctly to drive the ‘sound card’ (in your case the USB device) with bit-perfect input.

I am not aware of any other tooling/info that can be retrieved from the snd-usb-audio driver, but that is where some more details could be retrieved from.

Certainly what was said by matjans would be the ideal test, but my intention is simply to verify that the depth of the word (bit) and sample rate (kHz) are not altered in the output stream to the dac (no oversampling and no upsampling).

I’m not sure it’s the right thing, but looking for alsa I found references to the file /proc/asound/card*/ stream0 in which, while playback, the “Momentary freq” parameter shows the sample rate and the “Altset” shows the format used (16-24-32 bit).

Is the right way?