[mythtv-users] YAAQ (Yet Another ALSA Question)

[Stephen Tait]

>
>>Wow - you've pointed out how little I know about ALSA! I shall give the 
>>docs a peruse (obviously, googling for "alsa" and "mixer" and the like 
>>brought up rather alot of irrelevant pages); I had never even heard of 
>>ALSA control functions before. Since I'm using an Audigy, I guess this 
>>will be pretty well documented (AFAIK, the emu10k1 cards are the only 
>>ones currently available that have a hardware mixer supported under Linux).
>
>Oh.  Here we've encountered a little "terminology" problem.  The term 
>mixer has multiple meanings.
>
>In the context you've mentioned, the term "hardware mixer" is referring to 
>electronics on the sound card that mix multiple sound streams into 
>one--basically, allowing multiple applications to send sound data 
>concurrently to the same device.  The sounds from both applications are 
>played simultaneously (i.e. allowing you to hear your Myth box's beeps and 
>clicks while watching TV--which can be both good--if it's an alarm telling 
>you to go to work--and bad--if you're really into the show ;).
>You are correct that very few cards have these "hardware stream mixers" 
>and/or hardware stream mixers with Linux support.  Instead, people with 
>cards lacking hardware stream mixers may use "server" applications like 
>JACK, esd, artsd, or simply ALSA's dmix plugin.

That's what I meant (just didn't word it precisely enough!) ; I've done 
enough reading up on ALSA to kinda know the terminology, and it's cos of 
the availability and Linux excellence of the audigy that I always go for 
it. I remember my first experiences in Linux with an AC97 chip... 
*shudders*... all those damned lockups when two apps tried to make a noise 
at the same time. I didn't know the direct distinction between hardware 
mixer and hardware stream mixer - thanks!


>However, in the context of my statement, "alsamixer is a program (software 
>mixer) used to send instructions to the ALSA driver requesting it send 
>instructions to the sound card's hardware mixer," the term "hardware 
>mixer" refers to the electronics on the sound card--which ALSA refers to 
>as the "control device"--that control the various sound inputs and 
>outputs.  This includes, for example, the Master and PCM volume.
>Almost all sound cards have this type of hardware mixer (one notable 
>exception is the rme9652).  Note, also, that technically speaking, the 
>"control device" includes the hardware mixer (not the hardware stream 
>mixer) /and/ other controls (i.e. digital I/O sync indicators, sample 
>clock source switch, etc.), so the hardware mixer is only a subset of the 
>controls available through ALSA's control device.

OK, I didn't know ALSA could control the sound cards hardware mixer 
directly - that's very cool indeed. Unless this is normal. But then IANAP 
and IAAVRAU*.


>Therefore, I recommend searching on "ALSA" and "control device" or "ALSA" 
>and "ctl-device."  This way, you're using a more specific (and less 
>common) term to narrow the search.
>
>OK.  My plan was actually to clear up confusion, but I may have had the 
>opposite effect.  HTH.

Don't worry, I shall go off in search of ALSA goodness with a fresh new 
step! Bit academic if Myth doesn't support it yet, but it'll no doubt come 
in handy for my other desktop boxen.

>Gotta go.  I'm hungry for some toast with strawberry jam.
>
>Mike

Hope you enjoyed it. Being a brit, I prefer it with scones and earl grey 
myself. Whilst watching the cricket, old bean.



*I am a very recent ALSA user