[PlanetCCRMA] soundblaster live resampling?

M P Smoak smoak@mis.net
Thu Feb 10 09:37:02 2005

On Thursday 10 February 2005 07:57, Crispin wrote:
> >   im trying to setup a planet box that has an old pci
> > soundblaster live...
> >  according to the alsa soundcard matrix, this card has its
> > "Output always resampled to 48khz" ...  is this a bad thing?
> >  im definitely a newbie with audio technical stuff, sorry
> > for the dumb question..
> Not a dumb questions by my standards (cue laughter from the
> rest of the list)...  What the resampling means in theory is
> not a lot.  In practise however, after a minute or two of
> recording the sound starts crackling badly and is unusable. 
> I'm told this is because of a bug in the resampling routines
> (by Creative maybe).

I've heard this on this list before but I never seen anyone give any
real data or references to the "bug" story.  I've used a sblive for
almost 2 years now;  recording with reZound running Planet CCRMA/RH9.
And I'm real satisfied with the results I'm getting.  Usually I'm
recording from an internet radio stream or from a cd; recently I've
been recording some of our groups players with simple setups (for 
example, guitar player with vocal mic and mic of his amp).  For our
purposes, the sblive is good enough for now.

> This can be avoided so long as you *always* run jack and use
> audio at 48KHz, which I do, and it's fine.

I'm not yet using jack at all, nor Ardour;  I'm waiting on FC?? to
get more stable.

> > also, anyone using this card and getting good results for
> > recording live
> > audio and midi?  i was looking into a firewire audio
> > interface, but after
> > looking through the archives, looks like they are not
> > supoprted by alsa...
> Yup, works fine for me!  Never tried recording audio and midi
> together though.  It's mostly stable with about 21ms latency.

I ran a quick test this morning to confirm what I've seen before.
Setup was reZound with qamix recording from an internet radio stream
(Univ. GA 128kb) and midi using sblive soundfont.

I setup in qamix with capture-source Mix and the Capture slider at 
46 and Activate checked; AC97 at 100; Wave Capture and Music Capture
not activated (setting don't seem to matter).  In the Playback section
of qamix: PCM = 100, Wave = 63, Music =42; I always leave PCM at 100
and the settings of Wave and Music do effect the record level DO 
effect the record level in reZound (don't ask me why).  

I recorded the music stream for awhile and then played along with it
on the midi keyboard for a bit.  I played back the result in rezound,
saved it, then saved it as an ogg file with quality level 1.0 (I think
this is lossless compression), then reloaded the rezound rez file and
saved it as a wav file.

I saw what I've seen before.  In rezound, no clicks/pops while recording.
Clicks/pops on playback in rezound that appear to be random and vary in
location on later playbacks.  No clicks/pops on playback of the ogg or
wav files using alsaplayer.  To my ear, they sound very nice, execept for
my poor keyboard playing :).

So I'm wondering if the sblive clicks/pops story has any basis in fact.
I'm sure not hearing it with any consistency at all.

Marv   in Lex, KY