[alsa-devel] Hercules P32 DJ: severe sound distortion during MIDI transfers
Takashi Iwai
tiwai at suse.de
Fri Mar 22 15:58:23 CET 2019
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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