[ardour-users] 48 channels on ardour

Thomas Vecchione seablaede at gmail.com
Tue Jul 17 22:48:19 PDT 2007


PS Obviously what I quoted above was 24/96K and I already mentioned 24
tracks on a single HD was unreliable for recording purposes.  If I was doing
24/48K the 24 tracks would be no problem and I could probably get 36 without
a problem.

        Seablade

On 7/17/07, Thomas Vecchione <seablaede at gmail.com> wrote:
>
> Well I can tell you what I am running.
>
> Currently:(Hopefully to be upgraded soon) a
>
> 1.6 GHz Opteron N-Force 4 Chipset(One of the few that didn't have problems
> with PCI-E and audio)
> 1 Gig of Ram.
> RME HDSP 9632 Interface
> GeForce 6600 PCI-E
> Assorted HDs(All 7200 RPM):
>    1 200 gig system drive SATA
>    1 200 gig playback(At the moment) IDE
>    And whatever else I might dig up as the need arises;)
>
> As you can see, my computer is not that much larger spec'd than  yours.
> What primarily is going to make the difference is having a decent set up
> system (On Linux a Realtime Kernel etc.) and HD availiability.  Running
> Playback/Record/ and your System off one HD will kill your performance VERY
> fast.  Try to get your System on One HD and your audio on another as a
> minimum, 2 HDs would be better, one for recording to, one for playback, if
> you do tracking a lot.  RAID arrays aren't really a bad idea either if you
> have the drives, though obviously, as you can see from my specs, not
> absolutely necessary.
>
> If you are in Ardour, if the problem is your HD performance, it will tell
> you.  A warning message will pop up saying your HD was unable to keep up.
> If your problem is xruns(dropouts) and playback continues, chances are your
> problem could be solved by ensuring you have realtime capabilities as that
> user, as otherwise what can happen is an interrupt triggered by other
> software will override your audio, and then you will drain your buffer
> before your audio gets a chance to work again.  That is what realtime
> preemption helps with, your audio card and software will preempt other
> software as needed.  Or at least that is my understanding;)
>
>          Seablade
>
> On 7/17/07, John Emmas <johne53 at tiscali.co.uk> wrote:
> >
> > I'd be interested to know what hardware you guys are running to get
> > 24 & 48 channels.  To be honest, my copy of Ardour often struggles to
> > play just 4 channels simultaneously.
> >
> > "Struggles" is probably an exaggeration but I do get occasional glitches
> >
> > such as a short 'hole' in the sound or an occasional 'skip'.  I've never
> > timed how often these happen but I doubt that I could replay 10 whole
> > minutes of audio without encountering at least 1 glitch.
> >
> > My hardware is pretty old but not unrespectable.  I have a 1.2GHz Athlon
> > with 512MB of RAM, but my disks are just standard EIDE types (though
> > reasonably fast).  I'm running OpenSuse 10.2 with Jacklab and an RME
> > HDSP9632 sound card.  Enough to run 4 x simultaneous channels without
> > encountering problems, I'd have thought.  Maybe I need to tweak
> > something??
> >
> > Just out of interest, what is considered a 'minimum spec' for say, a 24
> > channel system?
> >
> > John
> >
> >
> >
> > ----- Original Message -----
> > From: "John Rigg" <au at sound-man.co.uk>
> > To: "Kevin Cosgrove" < kevinc at doink.com>
> > Cc: <ardour-users at lists.ardour.org>
> > Sent: 17 July 2007 23:04
> > Subject: Re: [ardour-users] 48 channels on ardour
> >
> >
> > > On Tue, Jul 17, 2007 at 02:17:44PM -0700, Kevin Cosgrove wrote:
> > >>
> > >> On 17 July 2007 at 20:04, John Rigg <au at sound-man.co.uk> wrote:
> > >>
> > >> > Yep. You'd have to decide if you really need to use 96kHz rather
> > >> > than 48kHz. With something like a Delta 1010, most of the potential
> > >> > increase in quality at 96kHz is wiped out by the increased clock
> > >> > jitter, so it isn't really worth using more than 48kHz with that
> > >> > particular hardware.
> > >>
> > >> Very interesting.  Is there much additional jitter from trying to
> > >> sync multiple units, or is the internal jitter of one unit enough to
> > >> degrade the quality?  How are you determining the quality differences
> >
> > >> between 48kHz and 96kHz?  Are you looking at the noise floor?  Or,
> > >> maybe you've run a test like "effective bits"?  See
> > >>
> > http://www2.tek.com/cmswpt/tidetails.lotr?ct=TI&cs=Application+Note&ci=4405&lc=EN&from=rss
> > >
> > > I haven't done extensive comparisons between 48kHz and 96kHz,
> > > but I didn't hear enough of a difference between them to justify
> > > doubling the disk bandwidth and space.
> > >
> > > The Delta 1010 does have a jittery clock implementation. That's what
> > > happens when the clock is on the PCI card and the converters are at
> > > the other end of a 3m cable, with HF losses and crosstalk with all
> > > the other signals in the cable contributing to jitter. I got a
> > > noticeable improvement in audio quality just by replacing the 3m
> > > host cables with 1m ones.
> > >
> > > Regarding jitter when syncing, the 1010s sound better when using
> > internal
> > > clock than when synced via either BNC or S/PDIF. If I don't need more
> > > than eight channels (eg. when overdubbing) I run jackd with only one
> > > Delta 1010, set to internal clock. This situation can't be completely
> > > remedied by using a high quality external clock, because jitter occurs
> > > in the cable and the Delta 1010 hasn't got very good jitter
> > attenuation
> > > on its S/PDIF or wordclock inputs. It can be minimised by syncing with
> >
> > > very short, well-shielded cables with low capacitance.
> > >
> > >>
> > >> > Yes. At least one user on these lists is using it for 64 channels.
> > >> > I'm currently using three Delta 1010s for 24 tracks. It's reliable
> > >> > and I don't get xruns (I use large period size and monitor from the
> > >> > 1010s' hardware outputs for `zero latency' monitoring though).
> > Having
> > >> > said that,
> > >>
> > >> Are you sync'ing your three via the BNC sync connectors or through
> > >> the S/PDIFs?
> > >
> > > When using all three 1010s I clock them from an Audiophile 2496 card
> > > (also ice1712) in the same box, via a home-made 3-way S/PDIF splitter.
> >
> > > That way all three 1010s receive their clock signals at the same time.
> > > As a bonus the 2496 also bumps the 1010s off the IRQ that is shared by
> > the
> > > graphics and network adaptors onto individual IRQs of their own. I'm
> > not
> > > using the 2496 for I/O in this configuration.
> > >
> > > This is getting a little OT, but feel free to email me off list if you
> > > have more 1010-specific questions.
> > >
> > > John
> > > _______________________________________________
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>
>
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