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From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Anssi Hannula <anssi.hannula@iki.fi>, Takashi Iwai <tiwai@suse.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>,
	alsa-devel@alsa-project.org, dri-devel@lists.freedesktop.org,
	Jaroslav Kysela <perex@perex.cz>, Mark Brown <broonie@kernel.org>,
	Yakir Yang <ykk@rock-chips.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC v2 10/13] sound/core: add DRM ELD helper
Date: Thu, 7 May 2015 11:41:03 +0100
Message-ID: <20150507104102.GA2067@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <554A493C.5080106@iki.fi>

On Wed, May 06, 2015 at 08:02:52PM +0300, Anssi Hannula wrote:
> 05.04.2015, 20:26, Russell King - ARM Linux kirjoitti:
> > On Sun, Apr 05, 2015 at 06:46:13PM +0200, Takashi Iwai wrote:
> >>
> >> One another question: don't we need to deal with the sample bits in
> >> sad[2]?
> > 
> > It should, but I'm very wary about doing that without seeing more
> > examples of real SADs.  Right now, all my examples only support
> > one SAD with either 2 channel or 6 channel audio at the standard
> > (basic) 32, 44.1 and 48kHz rates.
> > 
> > The HDMI / CEA specs are very loose in their wording about the
> > short audio descriptors.  I've no idea whether a sink can provide
> > (for example) descriptors such as:
> > 
> > 	LPCM, 6 channel 32, 44.1, 48kHz
> > 	LPCM, 2 channel, 32, 44.1, 48, 96, 192kHz
> > 
> > or whether have to describe that as a single descriptor.  I only
> > have two TVs to test with here.
> 
> For the record, yes, multiple LPCM SADs are relatively common, and I
> think I've seen some that offered more rates on a stereo SAD than on a
> multichannel SAD (like in your example).

Okay, so we "think" we've seen it in the wild...

> > What I'm concerned about is that when the ALSA parameter refining
> > starts, we start with (eg) 2-8 channels, 32-192kHz.  Given that,
> > if we invoke the channel restriction before the rate restriction,
> > we would end up limiting to 2 channel at 32-192kHz.  If we apply
> > the restrictions in the opposite order, we'd restrict to 6
> > channel, 32-48kHz.  Neither are obviously correct in this
> > circumstance, and I don't really see a way to solve it given my
> > understanding of the way ALSA's parameter refinement works.
> > 
> > I suspect this is why most HDMI drivers are implemented such that
> > they take the maximum capabilities over all SADs, which would end
> > up restricting audio in the above case to: up to 6 channels, at
> > 32, 44.1, 48, 96 and 192kHz, even though 6 channel @ 192kHz isn't
> > hasn't been indicated as supported.
> > 
> > Most of this is speculation though, based off what is in the
> > documentation.  As I say, I don't have enough real-world examples
> > to get a feel for what manufacturers _actually_ do to give a hint
> > as to how the documentation should be interpreted.

... so this is probably less than speculation.

So, ALSA gurus, how do we handle this?  How do we arrange the parameter
resolution such that ALSA can permit _either_ 2 channels at 192kHz or 6
channels at 48kHz, but not 6 channels at 192kHz?  Right now, I don't
see how that's possible.

-- 
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according to speedtest.net.
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  reply index

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-02  9:20 [RFC v2 0/13] dw_hdmi cleanups, audio preparation, helpers and ahb audio support Russell King - ARM Linux
2015-04-02  9:21 ` [PATCH RFC v2 01/13] drm: imx/dw_hdmi: move phy comments Russell King
2015-04-02  9:21 ` [PATCH RFC v2 02/13] drm: bridge/dw_hdmi: clean up phy configuration Russell King
2015-04-02  9:21 ` [PATCH RFC v2 03/13] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator() Russell King
2015-04-02  9:21 ` [PATCH RFC v2 04/13] drm: bridge/dw_hdmi: use drm_hdmi_avi_infoframe_from_display_mode() Russell King
2015-04-02  9:21 ` [PATCH RFC v2 05/13] drm: bridge/dw_hdmi: simplify hdmi_config_AVI() a little Russell King
2015-04-02  9:21 ` [PATCH RFC v2 06/13] drm: bridge/dw_hdmi: remove mhsyncpolarity/mvsyncpolarity/minterlaced Russell King
2015-04-02  9:21 ` [PATCH RFC v2 07/13] drm: bridge/dw_hdmi: introduce interface to setting sample rate Russell King
2015-04-02  9:21 ` [PATCH RFC v2 08/13] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio Russell King
2015-04-02  9:22 ` [PATCH RFC v2 09/13] drm/edid: add function to help find SADs Russell King
2015-04-02  9:22 ` [PATCH RFC v2 10/13] sound/core: add DRM ELD helper Russell King
2015-04-05 15:57   ` Takashi Iwai
2015-04-05 16:20     ` Russell King - ARM Linux
2015-04-05 16:46       ` Takashi Iwai
2015-04-05 17:26         ` Russell King - ARM Linux
2015-05-06 17:02           ` Anssi Hannula
2015-05-07 10:41             ` Russell King - ARM Linux [this message]
2015-05-07 11:11               ` Lars-Peter Clausen
2015-05-08 10:56           ` [alsa-devel] " Jyri Sarha
2015-05-08 11:42             ` Russell King - ARM Linux
2015-05-05 22:35     ` Mark Brown
2015-05-06  8:58       ` Liam Girdwood
2015-05-08 13:16   ` [alsa-devel] " Jyri Sarha
2015-05-08 13:27     ` Russell King - ARM Linux
2015-05-08 13:37       ` Jyri Sarha
2015-04-02  9:22 ` [PATCH RFC v2 11/13] sound/core: add IEC958 channel status helper Russell King
2015-04-02  9:22 ` [PATCH RFC v2 12/13] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-04-02  9:22 ` [PATCH RFC v2 13/13] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King
2015-05-09 10:25 ` [PATCH v3 0/13] dw_hdmi cleanups, audio preparation, helpers and ahb audio support Russell King - ARM Linux
2015-05-09 10:25   ` [PATCH 01/13] drm: imx/dw_hdmi: move phy comments Russell King
2015-05-09 10:26   ` [PATCH 02/13] drm: bridge/dw_hdmi: clean up phy configuration Russell King
2015-05-22 15:19     ` Yakir
2015-05-09 10:26   ` [PATCH 03/13] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator() Russell King
2015-05-22 15:22     ` Yakir
2015-05-09 10:26   ` [PATCH 04/13] drm: bridge/dw_hdmi: use drm_hdmi_avi_infoframe_from_display_mode() Russell King
2015-05-09 10:26   ` [PATCH 05/13] drm: bridge/dw_hdmi: simplify hdmi_config_AVI() a little Russell King
2015-05-09 10:26   ` [PATCH 06/13] drm: bridge/dw_hdmi: remove mhsyncpolarity/mvsyncpolarity/minterlaced Russell King
2015-05-09 10:26   ` [PATCH 07/13] drm: bridge/dw_hdmi: introduce interface to setting sample rate Russell King
2015-05-22 15:26     ` Yakir
2015-05-09 10:26   ` [PATCH 08/13] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio Russell King
2015-05-22 15:28     ` Yakir
2015-05-09 10:26   ` [PATCH 09/13] drm/edid: add function to help find SADs Russell King
2015-05-09 10:26   ` [PATCH 10/13] sound/core: add DRM ELD helper Russell King
2015-05-22 12:20     ` [alsa-devel] " Mark Brown
2015-05-22 13:15       ` Russell King - ARM Linux
2015-05-22 13:30         ` Takashi Iwai
2015-05-22 13:53           ` Russell King - ARM Linux
2015-05-22 13:54             ` Takashi Iwai
2015-05-22 14:00               ` Russell King - ARM Linux
2015-05-22 14:02                 ` Takashi Iwai
2015-05-22 14:05                   ` Takashi Iwai
2015-05-22 16:12                     ` Russell King - ARM Linux
2015-05-09 10:26   ` [PATCH 11/13] sound/core: add IEC958 channel status helper Russell King
2015-05-22 12:40     ` Mark Brown
2015-05-09 10:26   ` [PATCH 12/13] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-05-09 16:49     ` [alsa-devel] " Anssi Hannula
2015-05-09 16:55       ` Russell King - ARM Linux
2015-05-09 17:07         ` Anssi Hannula
2015-05-09 17:40           ` Russell King - ARM Linux
2015-05-09 17:53             ` Russell King - ARM Linux
2015-05-09 17:55             ` Anssi Hannula
2015-05-09 18:11               ` Russell King - ARM Linux
2015-05-10 18:59                 ` Anssi Hannula
2015-05-10 19:33                   ` Russell King - ARM Linux
2015-05-10 20:47                     ` Anssi Hannula
2015-05-11 15:58                     ` Mark Brown
2015-05-09 10:26   ` [PATCH 13/13] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King
2015-05-27 10:43     ` Daniel Vetter
2015-05-27 11:43       ` Mark Brown
2015-05-27 17:31       ` Russell King - ARM Linux
2015-05-27 21:29         ` Daniel Vetter
2015-05-27 21:44           ` Russell King - ARM Linux
2015-05-28  6:43             ` Daniel Vetter
2015-05-28  4:56         ` [alsa-devel] " Takashi Iwai

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