Re: Hercules P32 DJ: severe sound distortion during MIDI transfers

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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@xxxxxxx> 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@xxxxxxx> 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@xxxxxxx
>                      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@xxxxxxxxxxxxxxxx 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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