Dne 24. 06. 20 v 9:45 Takashi Iwai napsal(a):
On Wed, 24 Jun 2020 01:26:36 +0200,
Harsha Priya wrote:
External HDMI receivers have analog circuitry that needs to be powered-on
when exiting standby, and a mechanism to detect PCM v. IEC61937 data.
These two steps take time and up to 2-3 seconds of audio may be muted
when starting playback.
Intel hardware can keep the link active with a 'silent stream', so that
the receiver does not go through those two steps when valid audio is
transmitted. This mechanism relies on an info packet and preventing the
codec from going to D3, which will increase the platform static power
consumption. The info packet assumes a basic 2ch stereo, and the silent
stream is enabled when connecting a monitor. In case of format changes the
detection of PCM v. IEC61937 needs to be re-run. In this case there is no
way to avoid the 2-3s mute.
The silent stream is enabled with a Kconfig option, as well as a kernel
parameter should there be a need to override the build time default.
I'm not sure whether the module option is the best interface.
An alternative is a mixer element that controls dynamically. Then
it'll be per card unlike the module option.
+1, kcontrol seems the appropriate way to control this.
Jaroslav
--
Jaroslav Kysela <perex@xxxxxxxx>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.
