<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - Lack of hardware volume no longer supported with HifimeDIY Tiny" href="https://bugs.freedesktop.org/show_bug.cgi?id=99607#c7">Comment # 7</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - Lack of hardware volume no longer supported with HifimeDIY Tiny" href="https://bugs.freedesktop.org/show_bug.cgi?id=99607">bug 99607</a> from <a class="email" href="mailto:tanuk@iki.fi" title="Tanu Kaskinen <tanuk@iki.fi>"> Tanu Kaskinen</a> <pre>Sorry for slow reply, I have trouble keeping up with the pace of incoming emails... (In reply to Jerome from <a href="show_bug.cgi?id=99607#c6">comment #6</a>) > Sure, this policy makes sense. After digging more, the issue is mostly on > the hardware side. There may be a way to be more user friendly however, TBC. > > There are two levels of oddities for the hardware, at the device > architecture and USB levels. The device architecture is: > > ---------------------- ------------- > USB --->| PCM2706 Burr Brown |-- IEC958 --->| Sabre DAC |---> Analog out > ---------------------- ------------- Headset > | > V > Analog out > UNUSED! > > The PCM2706 is only used for its USB interface. It has an internal DAC with > an analog output, but this output is not used. Instead, the PCM2706 has a > digital output, which is used to feed another better DAC from Sabre. This > other DAC output is the device output (headset 3.5 mm jack). > > But at the USB level, only the PCM2706 is seen with a completely stock > configuration. Even the USB id is generic for the PCM2706, so there's no way > to identify this specific set-up. > > And the USB audio class descriptors of the PCM2706 do not even reflect its > internal set-up. It would have been possible to describe at the USB level > both analog and digital output, but that's not done. From the USB > descriptors, the PCM2706 is a simple pipe with just the analog output: > > -------------------- --------------- ----------------- > | USB input stream |---->| Mute+Volume |---->| Analog output | > -------------------- --------------- ----------------- > > There is indeed hardware volume support, but from the PCM2706 datasheet it > applies only to the (unused) analog output, not to the digital IEC958 > interface. > > I saw two changes when upgrading from Jessie to Stretch: > 1) selecting the analog profile used to give no sound, now it does > with a step volume effect; > 2) the IEC95 profile had disappeared. > > The first change (1) I now understand: it's just that the IEC958 output is > enabled too when the analog output is enabled. The driver level correctly > report a hardware volume control for the analog output. But it doesn't apply > to the actually used IEC958 output (per the PCM2706 datasheet). And when the > volume is set to 0, the mute is likely enabled and this does apply to the > IEC958 output too. So the observed behavior is OK. Enabling the IEC958 > output too confused me, but why not. What does "aplay -l" print? Your description sounds like on Jessie there were separate alsa PCM devices for analog and digital (likely "hw:x,0" for analog and "hw:x,1" for digital, with the latter mapped to "iec958:x"), but now there's only digital, which pulseaudio incorrectly guesses is analog (for analog stereo output, pulseaudio tries first "front:x" and if that doesn't work, pulseaudio tries "hw:x,0" and if that works, pulseaudio assumes that it's an analog device even if it isn't). > (I still don't understand why using the keyboard volume control switches to > software volume for a split second before going back to hardware, but it's a > minor point) > > The second change (2) was the real problem in my case. But after the > suggested work-around the IEC958 profile is back, and when using it all is > ok again. I set it as default profile, and it's sticky across reboots / plug > and unplug now. I didn't see it disappear again since. Which work-around are you referring to? Setting the card profile to "off" and loading module-alsa-sink? If that's the workaround, what does "the IEC958 profile is back" mean? If you load module-alsa-sink, that shouldn't have any effect on the set of available profiles on the card object. > Because the IEC958 output is not part of the USB description, this profile > must be added by a driver handling the PCM2706. I tried to grep around for > the Burr Brown id and this device family (270[4567]) in the kernel source > and ALSA data, but couldn't find where it is managed. The datasheet is not > clear either on how the digital output is controlled. So I don't understand > how this interface is handled and why it disappeared. I don't know all the details either, but since pulseaudio doesn't any more present a digital profile on the card, the "iec958" PCM device has apparently been removed for the card in the alsa configuration (shipped in alsa-lib). To verify, you can check the output of "aplay -L" - does it show that a device named iec958 exists?</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>