Mislabled SOX result?

[JonPike]

Hi all... been away for a while.  

Have been so busy with work, I haven't done much listening or looking around the 4.2 and update versions since I changed over to them.  

Last night I did a fair amount of fixing that (listening, anyway) and besides rediscovering how more quality music just might save my sanity in the face of things lately...
I also noticed something odd in the reporting of the output stream data rate.

What I see is when I look at the Audio Information screen,  no matter what bit depth I see,  I see 32bit output.  The bitrate matches what the input rate is reported as.   If I use SOX,  I see the bit rate changing,  but not the bit depth that SOX is supposedly resampling it to. It still says 32bit,  even though I'm resampling it to 24bit/*.  As I recall using the * would leave the bitrate the same as original,  so that was expected  but I'm surprised by the fixed 32bit depth.



Am running an Allo Boss 1.2,  RPi 3B 1.2,  Moode 4.2  2018-07-11.    Hmmm,  shouldn't that be 07-18 if the update worked?

I'm not sure if this is just a reporting error,  actually what's going on,  or what.  I am pretty sure I remember the reported bit depth and rates corresponding to what SOX was set to earlier,  after I already had the Boss.  Not sure if everything was the same after 4.2 and updating 4.2

Just did a check with more settings.  Sampling the RP radio feed,  incoming at 16b 44.1kbps,  SOX set for 24b 192k,  gives 32b 192k.  Setting to 16b 88.2k gives 32b 88.2k. At least the bitrate changes. 

Not hearing issues with the sound,  just wondering what's going on in the background.

[Tim Curtis]

Hi,

Some component in the audio pipeline wants 32 bit word length instead of 24 bit so its zero-padding the bit depth. Nothing to worry about. Often its the device driver that only accepts 16 or 32 bit word length.

The About screen or moode log should list the update and its date. The original release date remains unchanged.

-Tim

[JonPike]

Hi,

Some component in the audio pipeline wants 32 bit word length instead of 24 bit so its zero-padding the bit depth. Nothing to worry about. Often its the device driver that only accepts 16 or 32 bit word length.

The About screen or moode log should list the update and its date. The original release date remains unchanged.

-Tim

OK, looks like I did have a good update then,  I have an update with 7-18-2018.

But, I really think I remember the bit depth of the output stream matching the SOX resample depth. Or it matching the input stream depth, if you weren't using SOX to resample.  With this hardware. Same Pi, same DAC.  Only thing that changed is either the 4.0 - 4.2,  or 4.2 to update 7-18 that I recently did. 

Was there a driver change for the Allo Boss somewhere in those versions?

[Tim Curtis]

Its possible but you would need to ask Allo. Zero-padding 24 to 32 bits has occurred as far back as I can remember depending on the audio format or device for example some of the high-speed USB audio receivers only accept 32 bit word length.

[kit1cat]

I have just checked this on my original Boss dac, and the output is the same as the selected sox rate, except if I turn EQ on, then the output is 32 bit.

[JonPike]

I have just checked this on my original Boss dac, and the output is the same as the selected sox rate, except if I turn EQ on, then the output is 32 bit.

Aha!!  There's the clue...  and that's it!

Sure enough,  this is my headphone setup,  and I sometimes use the crossfeed feature.  And,  I've had it on latley, after mostly not using it.  I turn the crossfeed off...  and now the indicated output depth and rate matches the input,  or what SOX is supposed to be resampling it to,  if SOX is enabled.   So EQ and Crossfeed (which is a kind of EQ, amongst other things)  are the same in causing this behavior.

Wonder what's going on,  is SOX bypassed when EQ or Crossfeed is enabled?  Does some kind of resampling happen independently of SOX to make it 32 bit when these are on and SOX isn't,  or is it not really 32 bit when it says so?  Is SOX still doing something when it is on,  or is it getting bypassed somehow?

Odd,  but at least now we know how to turn it on and off...  and hopefully it will be quick and easy for Tim and folks to check out now.

[Tim Curtis]

The DSP EQ's and Crossfeed output to ALSA plughw (convert if needed) instead of ALSA hw (direct w/o conversion) like MPD uses because user feedback indicated that the DSP's failed in some cases with their devices when using ALSA hw (direct).

Its no worry if bit depth gets zero-padded to 32 bit. The original bits are left untouched and thus "bit-perfect".

-Tim