From: Clemens Ladisch <clemens@ladisch.de>
To: pl bossart <bossart.nospam@gmail.com>
Cc: alsa-devel@alsa-project.org
Subject: Re: IEC switch issues
Date: Wed, 23 Jun 2010 17:10:01 +0200 [thread overview]
Message-ID: <4C2223C9.2080602@ladisch.de> (raw)
In-Reply-To: <AANLkTik4XvRinUEUjqpqXdnxXFIcPGs9zcRk-_yf1xHW@mail.gmail.com>
pl bossart wrote:
>>> 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?
Because the hardware has this switch; the driver just exposes all
hardware features.
> If it cannot be used when you sent IEC-formatted data (be that PCM
> or AC3-formatted data), then why bother?
Some codecs allow looping back the ADC output to the SPDIF transmitter.
In these cases, disabling the SPDIF transmitter might be useful.
Regards,
Clemens
next prev parent reply other threads:[~2010-06-23 15:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-22 21:22 IEC switch issues pl bossart
2010-06-23 8:55 ` Pavel Hofman
2010-06-23 12:05 ` Clemens Ladisch
2010-06-23 13:21 ` Raymond Yau
2010-06-23 15:01 ` pl bossart
2010-06-23 15:10 ` Clemens Ladisch [this message]
2010-06-23 17:04 ` pl bossart
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