[alsa-devel] IEC switch issues

pl bossart bossart.nospam at gmail.com
Wed Jun 23 17:01:16 CEST 2010

>> If I play my AC3 data on my HDAudio/SPDIF output using the hw:0,1
>> device, I can use alsamixer/amixer to mute/unmute.
>> Now if I use the iec958: plugin, I can't control the mute switch any longer:
> Muting an AC-3 stream would require encoding a stream of silent PCM
> samples (no data is not the same as silence); therefore, the iec958
> plugin disallows muting.

Actually the problem happens also with plain PCM rendered on the
iec958 device.There's no way to use the IEC switch.
So why do we have an S/PDIF switch in the first place? If it cannot be
used when you sent IEC-formatted data (be that PCM or AC3-formatted
data), then why bother?
Allowing for mute doesn't have any impact on functionality, and it
prevents the user from muting with alsamixer or a gui. I find this
silly, or I am missing something.

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