[alsa-devel] Hercules P32 DJ: severe sound distortion during MIDI transfers
Guido Trentalancia
guido at trentalancia.com
Fri Mar 22 17:02:14 CET 2019
But the bandwidth taken by MIDI should be very small compared to the one taken by the 48KHz audio stream, so that sounds very strange !
Obviously it's the multiplexing of audio and MIDI which fails, but I am not much into the USB drivers, either audio or core...
The USB root hub should be 2.0, according to lsusb output:
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Sounds pointless to try other ports since they are all of the same kind...
The important point here is that, in my opinion, a USB core driver bug seems less probable that a USB audio driver bug because the affected range is very wide (4.12 - 5.0) and at the same time the USB core driver has been tested very widely everyday by virtually all Linux users.
What should I do next ?
Guido
> On the 22nd of March 2019 at 16.14 Takashi Iwai <tiwai at suse.de> wrote:
>
>
> On Fri, 22 Mar 2019 16:05:17 +0100,
> Guido Trentalancia wrote:
> >
> > I suppose the Fedora 29 kernels are included in the range I tested as broken,
> > i.e. 4.12 -- 5.0.
> >
> > So, there is something triggering it on my system and not the other, maybe the
> > USB system as pointed out by Clemens.
>
> You can try different USB ports, too, e.g. if there are both USB 3.0
> and 2.0 ports.
>
> > I'll make some research on the two USB systems...
> >
> > I would also like to try USB Audio driver from kernel 3.0.1.
> >
> > What else do you suggest?
>
> If any, the problem is rather about the USB core side (likely the host
> driver), not the USB audio driver. I can imagine some bandwidth
> management or iosc transfer problem.
>
>
> Takashi
>
> >
> > Guido
> >
> > Il 22 marzo 2019 15:58:23 CET, Takashi Iwai <tiwai at suse.de> ha scritto:
> >
> > On Fri, 22 Mar 2019 15:54:03 +0100,
> > Guido Trentalancia wrote:
> >
> > As already explained, I have tested the following kernels:
> >
> > - kernel 5.0.2 -----> BROKEN
> > - kernel 4.17.10 --> BROKEN
> > - kernel 4.12.9 ---> BROKEN
> >
> > So, it's been around for very long.
> >
> > What do you suggest doing?
> >
> > But which kernel is used for another user who can use without the
> > problem? I suppose they use the recent kernel with Fedora?
> >
> > I have found reports on the web about similar problems (with other audio
> > interfaces) with kernels>3.0.0.
> >
> > Such a regression should have been reported earlier, otherwise it
> > becomes more and
> > more difficult to catch up...
> >
> > thanks,
> >
> > Takashi
> >
> > Regards,
> >
> > Guido
> >
> > Il 22 marzo 2019 15:47:36 CET, Takashi Iwai <tiwai at suse.de> ha scritto:
> >
> > On Fri, 22 Mar 2019 14:44:48 +0100,
> > Guido Trentalancia wrote:
> >
> > Hello Takashi.
> >
> > I have carried out the test that you proposed...
> >
> > My reply follows your quoted text.
> >
> > On Fri, 22/03/2019 at 11.12 +0100, Takashi Iwai wrote:
> > On Fri, 22 Mar 2019 11:04:01 +0100,
> > Guido Trentalancia wrote:
> >
> > Hello Takashi,
> >
> > I am using the latest version of everything, including kernel and
> >
> > ALSA
> > userspace library / tools.
> >
> > The other user has exactly the same hardware and has tested same
> > firmware
> > (both 1.36 and latest
> > 1.46), but with Fedora 29 and it is working.
> >
> > Perhaps Fedora 29 has a different version of the ALSA library, I
> > will find
> > out, try to downgrade, test again and report back.
> >
> > Yes, that'd be really helpful. If aligning the software doesn't fix
> > the issue, it's either because of the hardware or the difference of
> > usage patterns.
> >
> > I have tested exactly the same ALSA userspace library and plugins
> > distributed by Fedora 29 and it does NOT work !
> >
> > As already explained, the usage pattern is
> > exactly the same between me
> > and the user which is not experiencing this severe problem.
> >
> > Also, the hardware is the same: Hercules P32 DJ (with exactly the same
> > firmware version 1.46 which is the latest).
> >
> > So, the conclusion is that it must be a kernel bug ! I was expecting
> > this, as already pointed out in previous messages.
> >
> > Did you test the
> > very same kernel, too? Without that confirmation, no
> > one can conclude that at all...
> >
> > If the kernel makes difference, you can try identify which kernel
> > version starts showing the problem, and at best, do git bisection.
> >
> > thanks,
> >
> > Takashi
> >
> > Can you please help me fix this bug since you wrote the driver and/or
> > are maintaining it ?
> >
> > Thanks,
> >
> > Guido
> >
> > thanks,
> >
> > Takashi
> >
> > Guido
> >
> > Il 22 marzo 2019 10:53:11 CET, Takashi Iwai <tiwai at suse.de> ha
> > scritto:
> >
> > On Fri, 22 Mar 2019
> > 10:17:17 +0100,
> > Guido Trentalancia wrote:
> >
> > It cannot be a firmware bug, as you say, because:
> >
> > - it does NOT happen on Windows!
> >
> > It doesn't mean that the device behaves correctly as
> > advertised.
> >
> > - it does NOT even always happen on Linux: other users
> > (with different kernel
> > / ALSA
> > library) are not experiencing the same problem;
> > - it happens with several firmware versions, including the
> > latest one (1.36
> > and 1.46).
> >
> > So it is either a bug in ALSA kernel driver, USB sound
> > driver (more likely) or
> > ALSA library.
> >
> > Now, you are in charge of the USB sound driver, can you
> > please double check??
> >
> > If it doesn't happen for other users with the very same device,
> > you'd
> > need to identify what's the difference
> > between your case and
> > others.
> > For example, if the difference of alsa-lib matters, you can try
> >
> > the
> > very same condition.
> >
> > This kind of bug can't be easily debugged without the actual
> > hardware, unfortunately.
> >
> > Takashi
> >
> > Regards,
> >
> > Guido
> >
> > Il 22 marzo 2019 09:55:52 CET, Takashi Iwai <tiwai at suse.de
> > ha scritto:
> >
> > On Thu, 21 Mar 2019 23:27:46 +0100,
> > Guido Trentalancia wrote:
> >
> > I wonder if this might be due to a bug in the
> > "USB Audio Driver for Alsa"?
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/t
> > orvalds/linux.git/tree/sound/usb
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/t
> > iwai/sound.git/tree/sound/usb
> >
> > More likely a buggy firmware of your USB audio device
> > :)
> >
> > From the driver implementation POV, both audio and
> > MIDI devices are
> > handled by individual endpoints, hence they shouldn't
> > conflict.
> >
> > Or another possibility would be some USB
> > host side
> > issue like the
> > bandwidth. But
> > it's a MIDI stream that is very low data rate, so this
> > sounds also unlikely...
> >
> > thanks,
> >
> > Takashi
> >
> > Guido
> >
> > On the 20th of March 2019 at 21.47 Guido
> > Trentalancia
> > <guido at trentalancia.com wrote:
> >
> > Hello.
> >
> > I am hitting a very serious bug (ALSA kernel
> > driver or ALSA library)
> >
> > when using the Hercules P32 DJ audio
> > interface.
> >
> > The sound is severely distorted during MIDI
> > transfers.
> >
> > To reproduce:
> >
> > + start playing something in a first
> > console:
> >
> > console1# AUDIODEV=hw:2,0 play audio.wav
> >
> > + the audio plays fine
> >
> > + now start "amidi" in a second console
> > while the above track is still
> > playing
> >
> > console2#
> > amidi -p hw:2,0,0 -d
> >
> > + the sound is now severely distorted
> > (basically noise, with some
> > hard-
> > to-distinguish features resembling the
> > original track) until "amidi"
> > is
> > interrupted !
> >
> >
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