From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Alexander E. Patrakov" Subject: Re: Radeon unconnected HDMI eats samples at 280 kHz Date: Sat, 20 Sep 2014 15:39:28 +0600 Message-ID: <541D4B50.5020207@gmail.com> References: <54198F38.30002@canonical.com> <5419FC9E.9010302@iki.fi> <541A5BCD.2040105@canonical.com> <541A8FA2.7090406@canonical.com> <541C31EE.4020101@canonical.com> <541C6C23.1040403@canonical.com> <541C73C8.3040606@gmail.com> <541CBDB0.4020408@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-lb0-f169.google.com (mail-lb0-f169.google.com [209.85.217.169]) by alsa0.perex.cz (Postfix) with ESMTP id 82E4C265647 for ; Sat, 20 Sep 2014 11:39:31 +0200 (CEST) Received: by mail-lb0-f169.google.com with SMTP id b12so4447139lbj.0 for ; Sat, 20 Sep 2014 02:39:31 -0700 (PDT) In-Reply-To: <541CBDB0.4020408@canonical.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: David Henningsson , "Deucher, Alexander" , Takashi Iwai Cc: Anssi Hannula , "alsa-devel@alsa-project.org" List-Id: alsa-devel@alsa-project.org 20.09.2014 05:35, David Henningsson wrote: > > > On 2014-09-19 20:19, Alexander E. Patrakov wrote: >> 19.09.2014 23:47, David Henningsson wrote: >>> If audio_enabled quickly changes to off and then on when there is a mode >>> change, it might make sense to *not* wake up the audio driver in this >>> case, as I assume that the audio capabilities on the HDMI TV will not >>> change just because the video mode changes. >> >> Unfortunately, they will. Some low-resolution video modes just don't >> have enough pixel clock to transfer the 7.1 audio signal at 192 kHz. See >> the table on page 105 (shown as 121 in some readers) of >> http://www.microprocessor.org/HDMISpecification13a.pdf , section "7.3.3 >> Video Dependency". > > Ok, I stand corrected. I wonder what the least ugly thing to do would be > if the user is currently running audio when this happens, e g, if the > user is running a game with background music, and goes to "video > settings" and switches mode. > > But if such thing would audio glitch anyhow, like it seems maybe we > should let the audio_enabled signal pass through to the audio side to > indicate a short disconnection. It's just not going to be that fun > if/when we implement reprobing the HDMI device on plug in. And also the > risk of the audio stream switching to somewhere else, like going from > HDMI to analog. I think it is appropriate to interrupt the audio stream only if it doesn't fit the new mode. Then snd_pcm_writei can return an error code - but I don't have a good candidate. Neither -EIO nor -ENODEV nor -ESTRPIPE quite fits the bill. -- Alexander E. Patrakov