[mythtv-users] AC3 passthrough

[Michael T. Dean]

On 06/13/2006 02:44 PM, Landon Clark wrote:
> On 6/12/06 10:24 AM, "Michael T. Dean" <mtdean at thirdcontact.com> wrote:
>> On 06/12/2006 01:12 PM, ldc online wrote:
>>     
>>>> I am trying to get ac3 pass thru to to work on my new mythtv box that
>>>> I setup over the weekend. In the setup screens, I enabled AC3 pass
>>>> through, but when I watch a DVD straight from a disc, I only get two
>>>> channel.  I have also tried using XINE instread of mplayer, but when I
>>>> set that speaker arrangment settings to pass through and
>>>> restart xine, I get an Audio Device is Unavailable error.  Clicking on
>>>> more in XINE, I
>>>> see the following possibly relevant messages:
>>>> Audio_decoder: error: unknown buffer type: 01060000
>>>> Audio_decoder: error: unknown buffer type: 04000000
>>>> Audio_decoder: error: unknown buffer type: 02990000
>>>>         
>> What do you have specified for the audio.device.alsa_passthrough_device
>> in ~/.xine/config?
>>
>> # device used for 5.1-channel output
>> # string, default: iec958:AES0=0x6,AES1=0x82,AES2=0x0,AES3=0x2
>> #audio.device.alsa_passthrough_device:iec958:AES0=0x6,AES1=0x82,AES2=0x0,AES3=
>> 0x2
>>
>> If the same as the above (or with the bottom line uncommented), try just
>> plain "iec958" instead.
> Thanks for the suggestion.  Tried that and got the same response.  Finally
> got it to work by setting the passthrough device to be dmix.  I am not sure
> if that is good or bad, but it works so I am going with it!

Heh.  That means that the device you've specified is not being used or 
your receiver is "upmixing" 2-channel to multi-channel output.  The 
direct-mixing plugin is only 2-channel capable, so any sound passed over 
it would be 2-channel only, and--as it manipulates the stream--would not 
be passthrough.

Mike