[LAU] Thinkpad R60 for Audio Update - Firewire Conflicts with Audio

[Pieter Palmers]

Robin Gareus wrote:
> 
> Dmitry Baikov wrote:
>> On 4/10/07, Robin Gareus <robin at gareus.org> wrote:
>>> PCMCIA is ok, but not great for low latency. (adds one extra interface
>>> between PCI bus & sound-card). - the cheap solution is to get a PCMCIA
>>> card for your hard-disk - instead of using the built-in firewire for the
>>> disk. - maybe you want to do that anyway. use the built-in firewire to
>>> an external audio-device and the PCMCIA for storage.
>> Quite the opposite.
>> PCMCIA is great for latency. That "extra" PCI bridge does NOT affect
>> audio latency.
>> Firewire latencies are bigger than PCI/PCMCIA and will always be. Ask
>> Pieter Palmers for details.
> 
> good point. now I start to remember the protocol mess and overhead of
> 1394 audio. - and hope I'll forget about it again soon.. ;)
> 
>> So if you are for low latency, PCI/PCMCIA is unbeatable.
>> If you want numbers, I can provide them for Echo Indigo IO and RME
>> MultifaceII.
> 
> why not? a LAU-Poll can launch a "known to work professional gnu/linux
> sound setups and their specs&tweaks"  wiki page.. I wanted to pull out
> some information of prev. emails and x-link archived emails to the
> linuxaudio.org wiki... maybe next weekend..
> 
>> Ask somebody to jdelay their Firewire card.
> 
> it's not easy to interpret jdelay's output, is it?
Stupid question maybe, but did you set it up correctly? It's hard to 
imagine that such a simple util would be broken for you but not for me.

Is the input gain correct?


> 
> i get a lot of those running jdelay at 48kSPS -f64 -n2 for the UA-25.
> 
>  24404.495 frames ?? Inv
>  24404.345 frames ??
>  24404.241 frames ?? Inv
>  24404.181 frames ??
> 
> sometimes it "flips" and displays
>  44664.987 frames ??
>  43225.215 frames ?? Inv
>   8585.183 frames ??
> or other weird jumps that all add up to 48k. Then goes back to repeat
> the 24400 pattern. - i can tell that 24400/48000 is not the latency ;p
> 
> and guess it means a total round trip latency of around 800 frames or 16 ms.
If the UA's latency is 800frames or 16ms @ 2x64, I can definitely say 
that FireWire is WAY better, as in: 400 frames less latency for the same 
buffer settings.

> 
> btw. if i move a headphone relative to the mic, jdelay allows to track
> its distance with about a 2cm accuracy. how cool!
Use a patch cable! I don't think jdelay is made with a Headphones->Mic 
setup in thought.

Pieter