[mythtv-users] Quick survey regarding passthrough device settings

Michael T. Dean mtdean at thirdcontact.com
Mon Apr 19 17:27:54 UTC 2010


On 04/19/2010 09:52 AM, Greg Oliver wrote:
> On Mon, Apr 19, 2010 at 5:54 AM, Jean-Yves Avenard wrote:
>    
>> As I'm currently rewriting the audio code once again with
>> foobum at gmail.com (adds supports for>  16 bits audio (E-AC3, TrueHD,
>> LPCM etc) and various channel configurations (stereo, 3.0, 4.0, 5.1,
>> 7.1)
>>
>> I am wondering on wheither we actually need the passthrough device in
>> the audio settings.
>>
>> On all my machines, it's always set as default, or the same physical
>> device as what's used in the main audio device....
>>
>> So I'm interested to know from people who used it with a different
>> value, why they did so and if they tried any different ways ...
>>      
> I have been using ttable entries in asoundrc to re-route 5.1 channels
> to stereo channels to overcome the problem of some audio inaudible on
> certain videos.
>
> Would there be something to alleviate this.  I have found that
> re-mixing is not fast enough on the revo 1600 though, so the current
> implementation has not worked for me with regards to playing videos
> with 5.1AAC to my stereo tv over hdmi..
>
> Not sure if this is relevant?
>    

I'm pretty sure this was part of the original design decision for 
specifying a different passthrough audio device--adding the ability to 
use different low-level audio processing facilities or routing for 
audio/non-audio.  Basically, it allows you to configure your ALSA 
filters/plugins/routing for different types of audio.  It also allowed 
users to specify IEC 958 status bits that they wanted/needed to specify 
for passthrough (as different receivers tended to be differently picky 
about things).

http://svn.mythtv.org/trac/ticket/1598
http://svn.mythtv.org/trac/changeset/10201
http://www.gossamer-threads.com/lists/mythtv/dev/206535#206535
http://svn.mythtv.org/trac/ticket/1608
http://www.gossamer-threads.com/lists/mythtv/dev/194225#194225

Note that I'm not saying we do or do not need to keep the setting.

Mike


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