Hi Norman,
On 07/19/2016 10:08 PM, Norman nolte wrote:
> I own a TEAC UD-H01 DAC. I'm aware that the UD-H01 has a strange/faulty
> feedback frequency behaviour which is fortunately already handled by a
> quirk in ALSA snd-usb-audio kernel module (git commit
> 7040b6d1febfdbd9c1595efb751d492cd2503f96). So first of all many thanks
> to Clemens Ladisch, Julien Benoist, Daniel Mack et al. who initially
> debugged the issue and patched the kernel.
>
> Unfortunately I still have problems which clicks and crackles even with
> patched kernels when playing distinct sound files on the TEAC and I'm
> curious if I'm the only one.
>
> I was able to reproduce the audio problems on different Linux
> distributions (Ubuntu, Debian, OpenELEC, Kodibuntu all running Kernels
> >= 3.13), host PCs (as well tested via Linux life CDs on my Windows
> machine which runs the TEAC on Windows 10 at least at 16bit/44.1 kHz
> without sound problems) and different input formats (using 16/24 bit
> 44.1/192 kHz sine wave signal stored in WAV file format and played via
> aplay). o I tried to debug the problem.
>
> At least my UD-H01 always seems to return "feedback frequency" values
> (which is actually the expected number of samples per data out transfer,
> right?) around the nominal value.
>
> When playing back 16/44.1 I receive e. g. feedback value 0x58320, which
> is (shifted right by 16 bit) 5,51 Samples per Microframe (each 125 us)
> or 44.099 kHz.
>
> I assume if the pcm buffer of the UD-H01 tends to underrun or overflow,
> its firmware simply increases or decreases feedback value by (integer)
> one sample which is represented by feedback value +/- 0x10000.
>
> The workaround introduced with commit
> 7040b6d1febfdbd9c1595efb751d492cd2503f96 by Clemens Ladisch fully
> eliminates(!) this +/- 0x10000 feedback response of the UD-H01:
>
> + if (unlikely(sender->udh01_fb_quirk)) {
> + /*
> + * The TEAC UD-H01 firmware sometimes changes the feedback value
> + * by +/- 0x1.0000.
> + */
> + if (f < ep->freqn - 0x8000)
> + f += 0x10000;
> + else if (f > ep->freqn + 0x8000)
> + f -= 0x10000;
> + } else if (unlikely(ep->freqshift == INT_MIN)) {
>
> Consequence for at least my copy of the TEAC DAC is that at buffer
> underruns still occur. I was able to confirm this using printk debugging
> in the the snd-usb-audio kernel module.
>
> I fixed my sound problems by replacing +/- 0x10000 in the code above by
> e.g. +/- 0x0F000. Other values might work as well of course (or might be
> even better for other copies/models of the TEAC DACs). This patch
> reactivates the feedback loop by mapping the hefty feedback of the
> UD-H01 back into a range which can be handled safely by the ALSA/USB
> isochronous feedback control loop. Here is the modified code (see:
> attached patch):
[...]
Thanks for reporting this! I will send a patch upstream to correct the
value.
> If someone who has sound issues with the TEAC is willing to test it, I
> can also provide .deb packages of the kernels for Debian 8.5.0 and
> Kodibuntu 14.0.
>
> Currently the patch is only activated for UD-H01 and other models
> sharing the same usb product id but it is possible that this patch might
> be useful for other TEAC DAC models (i.e. UD-501) as well.
Any idea what USB PID:VID these devices use?
Thanks,
Daniel
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