Bug 84515

Summary: [NV96] HDMI audio works, but has audio gaps or pauses
Product: xorg Reporter: Pekka Paalanen <ppaalanen>
Component: Driver/nouveauAssignee: Nouveau Project <nouveau>
Status: RESOLVED WORKSFORME QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium    
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
output of lspci -nn
none
dmesg 3.16.3 while HDMI audio working, with gaps none

Description Pekka Paalanen 2014-09-30 15:36:05 UTC 
Created attachment 107133 [details]
output of lspci -nn

I'm running 3.16.3-gentoo kernel with a
 nouveau  [  DEVICE][0000:01:00.0] BOOT0  : 0x096500a1
 nouveau  [  DEVICE][0000:01:00.0] Chipset: G96 (NV96)

On a whim, I decided to try HDMI audio. I plugged in the TV, and extended my desktop there. To my surprise, 'alsamixer' reports "Card: HDA Intel" and "Chip: Nvidia MCP77/78 HDMI".

In audacious' ALSA settings, I found a "PCM device" hw:0,3 labeled as "HDMI 0". When I choose that as the output and play a song:

- The laptop internal speakers, i.e. the whole normal analog audio output system, produces a loud static, which I have to mute in Alsamixer by muting "Speaker".

- The song comes out mostly fine on the TV! (Was this supposed to work??)

I found I can mute the HDMI audio in alsamixer by setting "S/PDIF" off. No other control I tried has any effect on it. That is ok for me.

Apart from the static in the laptop speakers, the primary annoying problem is that the HDMI audio has short gaps or pauses. I measured it by ear for a couple of minutes, and the gaps occur roughly 33 second intervals. The length of a gap is less than a second, maybe a half second.

This bug is about the gaps.

This is the same system as in my bug #60680 where we eventually got HDMI video output regression solved. You can find an old mmiotrace there, and VBIOS dump.
Comment 1 Pekka Paalanen 2014-09-30 15:36:57 UTC 
Created attachment 107134 [details]
dmesg 3.16.3 while HDMI audio working, with gaps
Comment 2 Pekka Paalanen 2014-09-30 15:45:37 UTC 
The gaps are not deterministic, sometimes it doesn't happen and then it starts to happen again.
Comment 3 Pekka Paalanen 2014-09-30 15:59:52 UTC 
On a quick test with mplayer, the gaps do not seem to come when watching a video.
Comment 4 Pekka Paalanen 2014-09-30 16:16:39 UTC 
I tried to verify if playing a video actually does prevent the gaps, but now I find it very hard to reproduce the gaps with the same procedure as they earlier came regularly at a half minute intervals.
Comment 5 Pekka Paalanen 2014-09-30 18:18:32 UTC 
I need to get an mmiotrace from the blob doing audio.

< imirkin_> start it up unplugged, then echo a mark, and then plug it in
< imirkin_> that _should_ be enough
< imirkin_> oh, and make sure stuff displays on there obviously
Comment 6 Pekka Paalanen 2017-02-23 08:58:38 UTC 
After two and a half years, I have still not produced an mmiotrace. I also haven't done things that would have suffered from the gaps.

So I suppose I can just close this report.

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