Re: [Qemu-devel] QEMU VNC Audio - All audio data null

[agraham <agraham@g-b.net>]

On 07/15/2012 12:21 AM, malc wrote:
> On Sun, 15 Jul 2012, agraham wrote:
>
>> On 07/15/2012 12:01 AM, malc wrote:
>>> On Sat, 14 Jul 2012, agraham wrote:
>>>
>>> [..snip..]
>>>
>>>>
>>>> /usr/bin/qemu-kvm -usb -no-fd-bootchk -M pc -enable-kvm -m 128 -drive
>>>> file=/Storage/Windows/Images/Clone_of_Windows-XP-x32,if=none,media=disk,cache=unsafe,aio=native,snapshot,format=qcow2,id=virtio-blk-pci0
>>>> -device
>>>> virtio-blk-pci,addr=0x05,bus=pci.0,drive=virtio-blk-pci0,id=storage0
>>>> -device
>>>> virtio-net-pci,mac=52:e0:0a:14:00:03,netdev=hostnet0,addr=0x09,bus=pci.0,id=virtio-net-pci0
>>>> -netdev tap,script=no,downscript=no,id=hostnet0 -usbdevice tablet -vga std
>>>> -vnc :1100,lossy -rtc base=localtime,clock=host -global
>>>> kvm-pit.lost_tick_policy=discard -chardev
>>>> socket,id=monitor,path=windows-xp-1.monitor,server,nowait -mon
>>>> chardev=monitor,mode=readline -pidfile windows-xp-1.pid -chroot
>>>> /var/mist/chroot -runas qemu -snapshot -S -daemonize -name windows-xp-1
>>>> -uuid
>>>> cc0df7d6-26e4-4c60-911e-cd107935c6e6 -boot order=c -cpu kvm32 -soundhw
>>>> ac97,es1370
>>>>
>>>> Replacing es1370 with sb16 or removing it does not change anything.
>>>
>>> Once again, works for me, not with the insane command line like above
>>> though, bisecting is your only option unless someone has bright ideas.
>>>
>> Are you using the AC97 driver?
>>
>
> It shouldn't matter, but i've used SB16 under DOS.
>
Bi-section complete :)

I've found the root cause and hopefully you should be able to reproduce 
the issue.

There was a configure option introduced called "--enable-mixemu".

--enable-mixemu          enable mixer emulation

Could you rebuild with this switch added to your configure, you should 
the experience the issue as I do.

The option was added in Fedora qemu-1.0-x which included QEMU-0.15-1 + a 
ton of patches. after rebuilding / removing patches /rebuilding etc.. as 
you advised, all patches where removed and the problem still existed! 
that lead me to the difference in the configure options.

which lead to:

http://git.qemu.org/?p=qemu.git;a=blob;f=audio/mixeng.c#l349

  349 void mixeng_volume (struct st_sample *buf, int len, struct 
mixeng_volume *vol)
  350 {
  351 #ifdef CONFIG_MIXEMU
  352     if (vol->mute) {
  353         mixeng_clear (buf, len);
  354         return;
  355     }

I see the words "mute" + "clear", which is what I originally experienced :)

I'm not a C programmer so cannot fix this myself, but I imagine that any 
mixemu code should do nothing if QEMU_AUDIO_DRV=none.


Interestingly:

# Copyright (c) 2004-2005 Vassili Karpov (malc)

Any connection with you?


Lastly, I think it would be more efficiency and bandwidth friendly to 
zero the length such that no data would be sent to other clients that do 
use this feature (I assume spice), after all there really is no point in 
sending zero bytes.

Even when zeros are sent to the sound device you will often here a click 
or a crackle for a fraction of a second, so by no sending anything you 
would avoid that.

Albert