On 18.02.2013 13:03, Takashi Iwai wrote:
At Sun, 17 Feb 2013 19:57:57 +0200, Anssi Hannula wrote:
On Sunday, February 17, 2013, Takashi Iwai tiwai@suse.de wrote:
At Sun, 17 Feb 2013 14:23:21 +0200, Anssi Hannula wrote:
17.02.2013 10:24, Takashi Iwai kirjoitti:
At Sat, 16 Feb 2013 22:59:40 +0200, Anssi Hannula wrote:
16.02.2013 18:40, Anssi Hannula kirjoitti: > Some HDMI codecs (at least NVIDIA
0x10de000b:0x10de0101:0x100100) start
> transmitting an empty audio stream as soon as PIN_OUT and
AC_DIG1_ENABLE
> are enabled. > > Since commit 6169b673618bf0b2518ce413b54925782a603f06 ("ALSA:
hda -
> Always turn on pins for HDMI/DP") this happens at first
open() time, and
> will continue even after close(). > > Additionally, some codecs (at least Intel PantherPoint HDMI)
currently
> continue transmitting HDMI audio even after close() in case
some actual
> audio was output after open() (this happens regardless of
PIN_OUT).
> > Empty HDMI audio transmission when not intended has the
effect that a
> possible HDMI audio sink/receiver may prefer the empty HDMI
audio stream
> over an actual audio stream on its S/PDIF inputs. > > To avoid the issue before first prepare(), set stream format
to 0 on
> codec initialization. 0 is not a valid format value for HDMI
and will
> prevent the audio stream from being output. > > Additionally, at close() time, make sure that the stream is
cleaned up.
> This will ensure that the format is reset to 0 at that time,
preventing
> audio from being output in that case. > > Thanks to OpenELEC developers and users for their help in
investigating
> this issue on the affected NVIDIA "ION2" hardware, and for
the initial
> bug report of the issue. Testing of the final version on
NVIDIA ION2 was
> done by OpenELEC user "MrXIII". Testing on Intel PantherPoint
was done
> by myself. > > Signed-off-by: Anssi Hannula anssi.hannula@iki.fi > Cc: stable@vger.kernel.org > --- > > This also supersedes the patch I attached yesterday as it
fixes both
> cases. > > I guess the alternative to this approach would be to fiddle
with
> AC_DIG1_ENABLE when preparing and closing the device, but
with a quick
> look that seemed to be possibly more complex since
AC_DIG1_ENABLE is
> already meddled with at quite a few places in hda_codec.c.
Hmm... actually, that would not be so much more complex, just
making
sure AC_DIG1_ENABLE is off in hdmi_add_cvt() (by e.g. zeroing AC_VERB_SET_DIGI_CONVERT_1) and making
snd_hda_spdif_ctls_unassign()
call "set_spdif_ctls(codec, spdif->nid, 0, -1);".
However, it would still mean that just a simple snd_pcm_open()
could
cause an empty stream to be output (if format is valid), since
iec958
controls are assigned at open() time, and iec958 mute controls AC_DIG1_ENABLE. Or we could add additional code in hda_codec.c
to
prevent AC_DIG1_ENABLE being set if prepare() has not been
called.
Is the problem fixed if you set codec->no_sticky_stream = 1?
The issue on NVIDIA reported by users, no, that flag is not used
in a
simple open()+close() path.
It is. The flag is used in hda_codec.c. It's a flag for setting FORMAT stuff, not the SPDIF status.
The only use I see there is in __snd_hda_codec_cleanup_stream(), but AFAICS that is not called by open/close callbacks of hdmi, since the stream is only allocated in prepare(). Am I missing something?
It changes the behavior of cleanup. The cleanup is implicitly called before close via hw_free.
Ah, indeed, that's what I was missing. Somehow I thought cleanup() was only called if prepare() was.
When cleanup callback isn't defined, snd_hda_codec_cleanup_stream() is invoked as default. And no_sticky_stream flag is evaluated there. Hence, it must influence on simple_hdmi case, too.
Right (though with "simple" I meant "prepare() not called", everything I wrote was about generic_hdmi).
My issue on Intel, yes.
Actually, the current behavior is intentional. There have been
bug
reports that just reopening a device causes the receiver not
reacting
immediately. In the worst case, it takes a few seconds to
sync. So we
introduced a mechanism to keep the PCM stream assignment.
Hmm.. If the intention is to keep a silent stream playing even
after
device has been closed, why was PIN_OUT disabled on close until
"ALSA:
hda - Always turn on pins for HDMI/DP" in December?
The intention isn't to keep the stream playing, but it keeps the STREAM tag. It's just a weird hardware implementation that it
keeps
playing. And, the feature was implemented far before the new
dynamic
SPDIF status control assignment and the dynamic pin down. So, it
got
broken by that stuff sometime ago.
Ah, so you mean something different with „lost sync„, I used that interchangeably with „hdmi stream stopped„. Can you explain the difference, to get us on the same page? :)
Some receivers seem to keep sync even if you stop the stream as long as the FORMAT tag isn't changed. That's the only point of the sticky PCM stream. It's not intended to keep the stream running.
I wonder what is the actual difference in the actual HDMI transmission between "stream running" and "sync kept". Any idea?
I'd say it's rather a bug of hardware or driver doing that. Maybe it's just for avoiding the out-of-sync situation.
Of course I can't tell if it is really just my receiver that handles your "sync kept" state as if the stream was running.
What makes harder in the case of HDMI/DP, it's not only about the hardware but related also with the video driver. I won't be surprised if different behavior is seen between the open-source and binary-only drivers, or between different driver versions. And, plus, the behavior depends on the receiver, too.
So, we always need to think of three things if we debug this kind of problems:
- HDMI audio codec
- Video driver, version
- Receiver hardware
Indeed.