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.
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.
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'd say it's rather a bug of hardware or driver doing that. Maybe it's just for avoiding the out-of-sync situation.
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
Takashi