[mythtv-users] Static noise from AC3 passthrough

Tue May 30 18:02:10 UTC 2006

Sorry, I just meant that I have default defined in asoundrc as
digital-hw (aka the same as digital).  But overriding the default and
specifying the device as digital or mixed-digital produces the same
results.

On a side note, specifying ALSA:spdif results in a device not found
error?  If this should be defined as basically the same thing as what
exists as digital in asoundrc it seems strange that this would occur?

Thanks for the suggestions thus far Mike, any other thoughts?

On 5/30/06, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> On 05/30/2006 11:32 AM, Michael T. Dean wrote:
> > With that asoundrc, you should never directly use the "devices"
> > "dmix-analog", "dmix-digital", "digital-hw", and "analog-hw".  They are
> > there simply for defining the ones you should use:  "mixed-analog",
> > "mixed-digital", "digital", and "analog".
> >
> > Therefore, use "digital".
> >
> I changed the wiki entry to include new, more descriptive comments in
> the .asoundrc.  (Basically, I put information in a comment at the top of
> the file that previously existed only in the text of the page or in
> comments spread throughout the .asoundrc.)  I highly recommend those
> using the .asoundrc from the wiki/from Jarod's page (which itself was
> from the wiki) get the new version.  I'm including a copy here (as
> asound.conf--appropriate for the /etc directory--but feel free to save
> it as ~/.asoundrc).
>
> Now, I'm changing the entry--which used to be nearly verbatim copy of
> one of my posts to the list, but now has other people's words in what it
> claims I wrote--to reference my post and include the important
> information in a context more appropriate for the wiki...
>
> Mike
>
>
>
> # ~/.asoundrc or /etc/asound.conf
> # ALSA configuration file
>
> ##### USAGE #####
> # Save this file as "~/.asoundrc" (for user-specific sound configuration) or
> # "/etc/asound.conf" (for system-wide sound configuration) and specify ALSA
> # device names ad described in the next section.
>
>
> ##### DEVICE NAMES #####
> # This configuration file defines four devices for use by the user.  Those
> # devices are "analog", "mixed-analog", "digital", and "mixed-digital".  The
> # user may also re-define "default" to be identical to one of the above-named
> # devices (i.e. to send all sound output to the digital output unless otherwise
> # specified).  Use the device names as described below:
> #  - "analog" outputs to the analog output directly and (at least on software
> #  sound cards) blocks other audio output.  After playback completes, "queued"
> #  sounds are output in sequence.
> #  - "mixed-analog" mixes audio output from multiple programs into the analog
> #  output (so you can hear beeps, alerts, and other noises while playing back
> #  an audio stream).
> #  - "digital" outputs to the digital output directly.  Since most (all?)
> #  digital outputs expect 48kHz PCM audio, this may not work for some playback
> #  (i.e. CD's--which are 44.1kHz PCM audio--or 32kHz audio streams from TV
> #  recordings, etc.).
> #  - "mixed-digital"
>
> # All other devices created within this file are used only by the configuration
> # file itself and should /not/ be used directly.  In other words, do not use
> # the devices "analog-hw", "dmix-analog", "digital-hw", or "dmix-digital".
>
>
> ##### IMPORTANT #####
> # To make this ALSA configuration file work with your sound card, you will need
> # to define the appropriate card and device information for the "analog-hw" and
> # "digital-hw" devices below.  You can find the card and device information
> # using "aplay -l".
>
>
> ##### Configuration File #####
>
> # Override the default output used by ALSA.  If you do not override the
> # default, your default device is identical to the (unmixed) "analog" device
> # shown below.  If you prefer mixed and/or digital output, uncomment the
> # appropriate four lines below (only one slave.pcm line).
> #
> # Note, also, that as of ALSA 1.0.9, "software" sound cards have been modified
> # such that their default "default" device is identical to the "mixed-analog"
> # device.  Whether using an ALSA version before or after 1.0.9, it does no harm
> # and has no affect on performance to redefine the device (even if the
> # redefinition does not change anything).  Also, by using this ALSA
> # configuration file, you once again have access to unmixed analog output using
> # the "analog" device.
> pcm.!default {
>   type plug
> ## Uncomment the following to use "mixed-analog" by default
>   slave.pcm "dmix-analog"
> ## Uncomment the following to use (unmixed) "digital" by default
> #  slave.pcm "digital-hw"
> ## Uncomment the following to use "mixed-digital" by default
> #  slave.pcm "dmix-digital"
> }
>
> # Control device (mixer, etc.) for the card
> ctl.!default {
>   type hw
>   card 0
> }
>
> # Alias for (converted) analog output on the card
> # - This is identical to the device named "default"--which always exists and
> # refers to hw:0,0 (unless overridden)
> # - Therefore, we can specify "hw:0,0", "default", or "analog" to access analog
> # output on the card
> # - Note that as of ALSA 1.0.9, "software" sound card definitions redefine
> # "default" to do mixing, meaning this device is different from "default" and
> # allows playback while blocking other sound sources (until playback
> # completes).
> pcm.analog {
>   type plug
>   slave.pcm "analog-hw"
> }
>
> # Control device (mixer, etc.) for the card
> ctl.analog {
>   type hw
>   card 0
> }
>
> # Alias for (converted) mixed analog output on the card
> # - This will accept audio input--regardless of rate--and convert to the rate
> # required for the dmix plugin (in this case 48000Hz)
> # - Note that as of ALSA 1.0.9, "software" sound card definitions redefine
> # "default" to do mixing, meaning this device is identical to "default" for
> # "software" sound cards.
> pcm.mixed-analog {
>   type plug
>   slave.pcm "dmix-analog"
> }
>
> # Control device (mixer, etc.) for the card
> ctl.mixed-analog {
>   type hw
>   card 0
> }
>
> # Alias for (converted) digital (S/PDIF) output on the card
> # - This will accept audio input--regardless of rate--and convert to the rate
> # required for the S/PDIF hardware (in this case 48000Hz)
> pcm.digital {
>   type plug
>   slave.pcm "digital-hw"
> }
>
> # Control device (mixer, etc.) for the card
> ctl.digital {
>   type hw
>   card 0
> }
>
> # Alias for mixed (converted) digital (S/PDIF) output on the card
> #  - This will accept audio input--regardless of rate--and convert to the rate
> #  required for the S/PDIF hardware (in this case 48000Hz)
> pcm.mixed-digital {
>   type plug
>   slave.pcm "dmix-digital"
> }
>
> # Control device (mixer, etc.) for the card
> ctl.mixed-digital {
>   type hw
>   card 0
> }
>
> # The following devices are not useful by themselves.  They require specific
> # rates, channels, and formats.  Therefore, you probably do not want to use
> # them directly.  Instead use of of the devices defined above.
>
> # Alias for analog output on the card
> # Do not use this directly--it requires specific rate, channels, and format
> pcm.analog-hw {
>   type hw
>   card 0
>   # The default value for device is 0, so no need to specify
> #  - Uncomment one of the below or create a new "device N" line as appropriate
> #    for your sound card or
> #  device 1
> #  device 4
> }
>
> # Control device (mixer, etc.) for the card
> ctl.analog-hw {
>   type hw
>   card 0
> }
>
> # Alias for digital (S/PDIF) output on the card
> # Do not use this directly--it requires specific rate, channels, and format
> pcm.digital-hw {
>   type hw
>   card 0
>   device 1
> #  - Comment out "device 1" above and uncomment one of the below or create a
> #    new "device N" line as appropriate for your sound card or
> #  device 2
> #  device 4
> }
>
> # Control device (mixer, etc.) for the card
> ctl.digital-hw {
>   type hw
>   card 0
> }
>
> # Direct software mixing plugin for analog output on the card
> # Do not use this directly--it requires specific rate, channels, and format
> pcm.dmix-analog {
>   type dmix
>   ipc_key 1234
>   slave {
>     pcm "analog-hw"
>     period_time 0
>     period_size 1024
>     buffer_size 4096
>     rate 48000
>   }
> }
>
> # Control device (mixer, etc.) for the card
> ctl.dmix-analog {
>   type hw
>   card 0
> }
>
> # Direct software mixing plugin for digital (S/PDIF) output on the card
> # Do not use this directly--it requires specific rate, channels, and format
> pcm.dmix-digital {
>   type dmix
>   ipc_key 1235
>   slave {
>     pcm "digital-hw"
>     period_time 0
>     period_size 1024
>     buffer_size 4096
>     rate 48000
>   }
> }
>
> # Control device (mixer, etc.) for the card
> ctl.dmix-digital {
>   type hw
>   card 0
> }
>
>
>
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