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