[Qemu-devel] Audio distortion

[Qemu-devel] Audio distortion

[Jan Paul Schmidt]

Hi there,

I'm currently playing around with Win95a and have audio distortion. I 
used the wav driver to get the audio output as file and looked at it. 
The audio data looks fine except when the audio becomes loud or in 
other words, reaches the full amplitude.

To make it more visible, instead of

    ____
   /    \
  /      \
/        \
           \       /
            \     /
             \___/

the data will be like this

    _ _
   /   \
  /     \
/       \
          \       /
           \     /
     _      \___/

Looks like some unhandled overflow or a wrong convertion.

The host is a Mac by the way and Qemu is at 0.6.1.

I would guess, the problem lies somewhere in sb16.c?
Someone knows this problem?
Someone working on it?
Is it PPC specific?

jps

Re: [Qemu-devel] Audio distortion

[Magnus Damm]

Hello,

On Wed, 19 Jan 2005 16:59:29 +0100, Jan Paul Schmidt <jps@fundament.org> wrote:
> Someone knows this problem?

Yeah, I have notived it while playing "Caesar 3" under Win98.

> Someone working on it?

Not me. =)

> Is it PPC specific?

I experienced it on a x86 host a few days ago with up to date CVS.  I
would love to try out things on my PPC host, but PPC host support for
Linux is badly broken in CVS right now.

/ magnus

Re: [Qemu-devel] Audio distortion

[Jan Paul Schmidt]

Am 20.01.2005 um 00:39 schrieb Magnus Damm:

> Hello,
>
> On Wed, 19 Jan 2005 16:59:29 +0100, Jan Paul Schmidt 
> <jps@fundament.org> wrote:
>> Someone knows this problem?
>
> Yeah, I have notived it while playing "Caesar 3" under Win98.
>
>> Someone working on it?
>
> Not me. =)
>
>> Is it PPC specific?
>
> I experienced it on a x86 host a few days ago with up to date CVS.  I
> would love to try out things on my PPC host, but PPC host support for
> Linux is badly broken in CVS right now.

So it sounds like it is not PPC host specific.

I compared CVS with 0.6.1. hw/sb16.c did not change and the only thing 
in audio/ that changed slightly is audio.c, audio_int.h and noaudio.c. 
But they don't look like they would fix the problem.

I'm guessing that the problem lies in the mixing engine but I did not 
find anything up to now. I hardly remember a problem in the rate 
conversion code in SoX and as Qemu uses a modified version of this, 
maybe the problem lies here?

jps

Re: [Qemu-devel] Audio distortion

[malc]

On Wed, 19 Jan 2005, Jan Paul Schmidt wrote:

> Hi there,
>
> I'm currently playing around with Win95a and have audio distortion. I used 
> the wav driver to get the audio output as file and looked at it. The audio 
> data looks fine except when the audio becomes loud or in other words, reaches 
> the full amplitude.
>
> To make it more visible, instead of

<snip>

> Looks like some unhandled overflow or a wrong convertion.
>
> The host is a Mac by the way and Qemu is at 0.6.1.
>
> I would guess, the problem lies somewhere in sb16.c?

Most likely in audio/mixeng_template.h (Johannes you know it
better, perhaps you can take a look?)

> Someone knows this problem?

No

> Someone working on it?

Not. Unless you provide the steps to reproduce the problem

> Is it PPC specific?

Hardly

>
> jps

-- 
mailto:malc@pulsesoft.com

Re: [Qemu-devel] Audio distortion

[Johannes Schindelin]

Hi,

On Fri, 21 Jan 2005, malc wrote:

> Most likely in audio/mixeng_template.h (Johannes you know it
> better, perhaps you can take a look?)

Shh! I wanted to stay hidden ;-)

> > Someone working on it?

Now, me. And you.

> Unless you provide the steps to reproduce the problem

This is a must. Please provide me something like a very short .wav which
you play in the guest, and which comes out distorted.

Ciao,
Dscho

Re: [Qemu-devel] Audio distortion

[Johannes Schindelin]

[-- Attachment #1: Type: TEXT/PLAIN, Size: 242 bytes --]

Hi,

I think I found a problem. However, this could be totally unrelated.
Please test the applied patch, and if it doesn't fix your problem, please,
please, pretty please, provide a short wav or whatever which shows the
problem!

Ciao,
Dscho

[-- Attachment #2: Type: TEXT/PLAIN, Size: 719 bytes --]

Index: audio/mixeng.c
===================================================================
RCS file: /cvsroot/qemu/qemu/audio/mixeng.c,v
retrieving revision 1.1
diff -u -r1.1 mixeng.c
--- audio/mixeng.c	7 Nov 2004 18:04:02 -0000	1.1
+++ audio/mixeng.c	21 Jan 2005 22:04:08 -0000
@@ -23,7 +23,6 @@
  * THE SOFTWARE.
  */
 #include "vl.h"
-//#define DEBUG_FP
 #include "audio/mixeng.h"
 
 #define IN_T int8_t
@@ -228,7 +227,7 @@
         icur = *ibuf;
 
         /* interpolate */
-        t = rate->opos & 0xffffffff;
+        t = (rate->opos & 0xffffffff)>>1;
         out.l = (ilast.l * (INT_MAX - t) + icur.l * t) / INT_MAX;
         out.r = (ilast.r * (INT_MAX - t) + icur.r * t) / INT_MAX;
 

Re: [Qemu-devel] Audio distortion

[Magnus Damm]

Hello,

Thanks for the patch but I it does not solve my problem. I don't know
the exact problem but speak with sharp s-sound seems distorted in some
way. I could email you a small wav tomorrow if that would help, let me
know. Now it is bedtime in Sweden.

Thanks,

/ magnus


On Fri, 21 Jan 2005 23:07:52 +0100 (CET), Johannes Schindelin
<Johannes.Schindelin@gmx.de> wrote:
> Hi,
> 
> I think I found a problem. However, this could be totally unrelated.
> Please test the applied patch, and if it doesn't fix your problem, please,
> please, pretty please, provide a short wav or whatever which shows the
> problem!
> 
> Ciao,
> Dscho
> 
> 
> _______________________________________________
> Qemu-devel mailing list
> Qemu-devel@nongnu.org
> http://lists.nongnu.org/mailman/listinfo/qemu-devel
> 
> 
> 
>

Re: [Qemu-devel] Audio distortion

[Johannes Schindelin]

Hi,

On Sat, 22 Jan 2005, Magnus Damm wrote:

> Thanks for the patch but I it does not solve my problem. I don't know
> the exact problem but speak with sharp s-sound seems distorted in some
> way. I could email you a small wav tomorrow if that would help, let me
> know.

Yes, please do that, else I'd have no idea how to reproduce your problem.

> Now it is bedtime in Sweden.

Same goes for Germany...

Ciao,
Dscho