Nouveau - Sep 2014 - [Bug 84515] New: [NV96] HDMI audio works, but has audio gaps or pauses

https://bugs.freedesktop.org/show_bug.cgi?id=84515

          Priority: medium
            Bug ID: 84515
          Assignee: nouveau at lists.freedesktop.org
           Summary: [NV96] HDMI audio works, but has audio gaps or pauses
        QA Contact: xorg-team at lists.x.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: ppaalanen at gmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: unspecified
         Component: Driver/nouveau
           Product: xorg

Created attachment 107133
  --> https://bugs.freedesktop.org/attachment.cgi?id=107133&action=edit
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.

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--- Comment #1 from Pekka Paalanen <ppaalanen at gmail.com> ---
Created attachment 107134
  --> https://bugs.freedesktop.org/attachment.cgi?id=107134&action=edit
dmesg 3.16.3 while HDMI audio working, with gaps

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--- Comment #2 from Pekka Paalanen <ppaalanen at gmail.com> ---
The gaps are not deterministic, sometimes it doesn't happen and then it
starts
to happen again.

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--- Comment #3 from Pekka Paalanen <ppaalanen at gmail.com> ---
On a quick test with mplayer, the gaps do not seem to come when watching a
video.

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--- Comment #4 from Pekka Paalanen <ppaalanen at gmail.com> ---
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.

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Pekka Paalanen <ppaalanen at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |NEEDINFO

--- Comment #5 from Pekka Paalanen <ppaalanen at gmail.com> ---
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

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Pekka Paalanen <ppaalanen at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEEDINFO                    |RESOLVED
         Resolution|---                         |WORKSFORME

--- Comment #6 from Pekka Paalanen <ppaalanen at gmail.com> ---
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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