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

From: agraham
Subject: Re: [Qemu-devel] QEMU VNC Audio - All audio data null
Date: Sat, 14 Jul 2012 13:55:14 +0100
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20111108 Fedora/3.1.16-1.fc14 Thunderbird/3.1.16

On 07/14/2012 11:44 AM, malc wrote:
On Sat, 14 Jul 2012, agraham wrote:

On 07/14/2012 03:17 AM, agraham wrote:
Hi Guys,

I've written a VNC client that implements the VNC QEMU Audio extensions.
Using QEMU 0.13 it works very very for remote sound, however after
upgrading to QEMU 1.1.0 the audio stream contains only bytes of zeros,
so this results in no sound on the client.

It is almost like the stream is muted by sending 0 bytes instead of the
actual data.

0: VNC: :SOUND: AudioOn
1: VNC: :SOUND: Received _QEMU_Audio_Server_Message: Operation: 1
2: VNC: :SOUND: Received _QEMU_Audio_Start
3: VNC: :SOUND: Received _QEMU_Audio_Server_Message: Operation: 2
4: VNC: :SOUND: Received _QEMU_Audio_Data 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Is there something new that needs to be done in order for the sound to
be pushed out, like some unmute mechanism?

I rebuilt QEMU 0.15.1 and sound worked but was very choppy, I think due
to some timer injection changes - but that's another issue.

Thanks in advance.


I've just rebuilt QEMU 1.0 (and all of its dependencies) and it has the same
problem (zero bytes), so some incompatibility was introduced between 0.15.1
and 1.1.0.

Anyone got any clues ?

Please try to bisect the issue.

My previous comment had a typo, it should have said: between 0.15.1 and 1.0. (not 1.1.0)

bi-section so far:

I suspect that one of the following patches is causing the issue, these are all added to QEMU 1.0 (by Fedora at least) and are included in 1.1.0 upstream.

# Spice volume control backports, all are upstream for 1.1
Patch501: 0501-audio-add-VOICE_VOLUME-ctl.patch
Patch502: 0502-audio-don-t-apply-volume-effect-if-backend-has-VOICE.patch
Patch503: 0503-hw-ac97-remove-USE_MIXER-code.patch
Patch504: 0504-hw-ac97-the-volume-mask-is-not-only-0x1f.patch
Patch505: 0505-hw-ac97-add-support-for-volume-control.patch
Patch506: 0506-audio-spice-add-support-for-volume-control.patch
Patch507: 0507-Do-not-use-pa_simple-PulseAudio-API.patch
Patch508: 0508-configure-pa_simple-is-not-needed-anymore.patch
Patch509: 0509-Allow-controlling-volume-with-PulseAudio-backend.patch

In order to use the QEMU VNC Audio for remote sound, you must
export QEMU_AUDIO_DRV=none, this indicates that you are not using a back-end.

QEMU_AUDIO_DRV=none is deceptive, but accurate, it tells QEMU not to connect to the QEMU host sound system. It does _not_ mean there is no sound.

Volume/mute control for VNC QEMU remote sound should _always_ be managed from the client side and should be on by default, but it looks like something is interfering with the stream from QEMU >0.15.1 on the server side and thus breaking the QEMU VNC extension.


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