The more people using Volumio2 on a C2 with a USB Audio DAC, the more reports we seem to get about clicks and pops (with kver 3.14.79).
We are talking about various DACs, eg. a USB Waveio, a Parasound Halo Integrated (ESS Sabre32 Reference ES9018K2M, a Chord Mojo and an FX-AUDIO-D-802.
On request, the users tried nrpacks=1 and/or changed cpu affinity.
Nothing seems to be a real fix, though it did improve a little for some.
Eg. the Waveio seems to be ok with changeing cpu affinity, all others still suffer.
As there were reports of Volumio pre-releases not having this these issues, I requested a few of the users to verify an older (pre-release) Volumio version from August
(stilll with kver 3.14.29, compiled on 22/04/2016).
Then some of them indeed reported back that the version with the "old" kernel did not have such problems, the sound appeared to be clean.
After that, I tracked all USB driver commits between version 3.14.29 from 22/04 and 3.14.79 from 08/12 and "stumbled" over:
- Code: Select all
Committed by mdrjr/ 24 May 2016
driver: drivers/amlogic/usb/dwc_otg/310/dwc_otg_hcd_queue.c
@@ -367,13 +367,13 @@ static int check_periodic_bandwidth(dwc_otg_hcd_t *hcd, dwc_otg_qh_t *qh)
* Max periodic usecs is 80% x 125 usec = 100 usec.
*/
- max_claimed_usecs = 100 - qh->usecs;
+ max_claimed_usecs = 125 - qh->usecs;
else
/*
* Full speed mode.
* Max periodic usecs is 90% x 1000 usec = 900 usec.
*/
- max_claimed_usecs = 900 - qh->usecs;
+ max_claimed_usecs = 1000 - qh->usecs;
if (hcd->periodic_usecs > max_claimed_usecs) {
DWC_INFO("%s: already claimed usecs %d, required usecs %d\n", __func__, hcd->periodic_usecs, qh->usecs);
@@ -724,4 +724,4 @@ int dwc_otg_hcd_qtd_add(dwc_otg_qtd_t *qtd,
return retval;
}
-#endif /* DWC_DEVICE_ONLY */
+#endif /* DWC_DEVICE_ONLY */
Just to see if it made any difference I reverted this commit and had it tested.
To my big surprise, the pops and crackling are reported to be gone for the WaveIO, the Chord Mojo and the Parasound.
The FX-Audio has other issues, as it appears not related.
To me it seems we had regression between kernel Version 3.14.29 (compiled 22/04/2016) and 3.14.79 (compiled 08/12/2016)
What was the reason for the commit listed above and is there anything we can do to help solving the usb audio issue?
-Gé-
is to make Volumio working with Kodi (videophile side...)
