[ATI RS690/780 HDMI] (Radeon driver) VLC audio becomes distorted without tsched=0

[Jani Uusitalo]

Bug #751265 describes the symptom: when VLC uses Pulseaudio for audio output, the sound from it becomes garbled after playing for a while, with heavy digital artefacts and echoing. Comment #23 in that report suggests modifying /etc/pulse/default.pa so that load-module module-udev-detect is followed by tsched=0. I've done that, and with it VLC seems to work fine with Pulseaudio. Furthermore, in comment #30 @David Henningsson prompted us suffering from this and with the tsched=0 workaround working to file our own reports for each specific hardware. This is my report.

I believe apport adds data about the hardware automatically. I'll add to that that for me this only occurs with the Radeon HDMI output; through the analog output (via headphones) the audio works fine. As Bug #864735 describes, Radeon audio is off by default in recent kernels, but I've re-enabled it by passing the radeon.audio=1 kernel commandline parameter.

If I switch to ALSA output for VLC (without tsched=0), VLC audio goes mute after a while. After some time of silence it sort of fast forwards itself to get up to sync with the video again. This keeps repeating, so it's not really a workaround.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: alsa-base 1.0.24+dfsg-0ubuntu3
ProcVersionSignature: Ubuntu 3.2.0-14.23-generic 3.2.3
Uname: Linux 3.2.0-14-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 1.91-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: jani 2717 F.... pulseaudio
 /dev/snd/pcmC1D3p: jani 2717 F...m pulseaudio
 /dev/snd/controlC0: jani 2717 F.... pulseaudio
 /dev/snd/timer: jani 2717 f.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'SB'/'HDA ATI SB at 0xfe8f4000 irq 16'
   Mixer name : 'Realtek ALC887'
   Components : 'HDA:10ec0887,1043837b,00100202'
   Controls : 43
   Simple ctrls : 20
Card1.Amixer.info:
 Card hw:1 'HDMI'/'HDA ATI HDMI at 0xfeae8000 irq 19'
   Mixer name : 'ATI RS690/780 HDMI'
   Components : 'HDA:1002791a,00791a00,00100000'
   Controls : 4
   Simple ctrls : 1
Card1.Amixer.values:
 Simple mixer control 'IEC958',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
CheckboxSubmission: 09ae689090491ca53449589269e4bfd8
CheckboxSystem: edda5d4f616ca792bf437989cb597002
Date: Sun Feb 5 23:38:14 2012
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release amd64 (20091027)
PackageArchitecture: all
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaPlaybackTest: ALSA playback test through plughw:HDMI failed
Symptom_Card: RS780 HDMI Audio [Radeon HD 3000-3300 Series] - HDA ATI HDMI
Symptom_Jack: Digital Out, HDMI
Symptom_Type: Digital clip or distortion, or "overdriven" sound
Title: [System Product Name, ATI RS690/780 HDMI, Digital Out, HDMI] Sound is distorted
UpgradeStatus: Upgraded to precise on 2012-01-17 (19 days ago)
dmi.bios.date: 08/12/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 2101
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: M4A78-EM
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: Rev X.0x
dmi.chassis.asset.tag: Asset-1234567890
dmi.chassis.type: 3
dmi.chassis.vendor: Chassis Manufacture
dmi.chassis.version: Chassis Version
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2101:bd08/12/2010:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnM4A78-EM:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion:
dmi.product.name: System Product Name
dmi.product.version: System Version
dmi.sys.vendor: System manufacturer

[David Henningsson (diwic)]

Hi Jani!

The reason radeon.audio is off by default is that they don't feel they've got it sufficiently bug free. So neither upstream nor Ubuntu supports it at this point. Does it work with the fglrx driver?

[Jani Uusitalo (uusijani)]

Hi David, thanks for responding. I tested fglrx just now and every time I launched VLC with audio, or in this case even Totem with audio, the X session went boom right before any sound came out. So if you meant "does it work without tsched=0 when using fglrx", I guess the answer is no. I'll attach the X log, although this crash is probably unrelated to this report. (I only use the free drivers myself so I won't bother to report this separately. It was pretty consistent and should be easily reproducible though.)

I didn't know whether the radeon.audio=1 kernel parameter matters when fglrx is in use, so I tried both with it and without it, with the same result (X crash).

The only thing audiowise that didn't crash the session was PA's speaker test (from the audio settings). It didn't make any sound either though.

Luckily, enabling Radeon audio in the kernel hasn't given me any problems on this setup, at least such that I could link to it. I do have Bug #917668 filed in, but it'll have to reoccur to get more data to see if that's connected.

[David Henningsson (diwic)]

Thanks. I'm afraid there isn't much to do at this point - there is a workaround (tsched=0), and the Radeon audio driver does not support HDMI officially.

[Marcus Tomlinson (marcustomlinson)]

This release of Ubuntu is no longer receiving maintenance updates. If this is still an issue on a maintained version of Ubuntu please let us know.

[Launchpad Janitor (janitor)]

[Expired for alsa-driver (Ubuntu) because there has been no activity for 60 days.]