Reducing XAP delay

[catalin66ro]

Hi all ! I have a problem. I use XAP as a final processor on a dedicated computer, with two soundcards. But I seems to have almos 1 second delay, wich is disturbing  for the one who is on air. How can I reduce the delay ?
My PC is a 2600+ Sempron, 512MB Ram

[jesseg]

unfortunately the latency only goes down to 1024 samples on input and output.  that\'s mainly the problem...  ideally it would have ASIO input & output with latency to down 64 samples.  then you should be able to only add about 1.5ms from soundcard input & output.  the rest of the latency would just be whatever XAP has.

i\'ve never bothered to test XAP latency.  mainly cos SS2 sounds better for the most part.  SS2 has some issues with the band 5 filtering that are somewhat fixed in XAP (or re-tuned is maybe a better word), but oh well.

[catalin66ro]

OK, I agree that SS2 sounds better, even has presets, but I still have a delay even with SS2. The truth is that i don\'t have an ASIO card, but here\'s how I\'ve done it: I use a PIII 1GHz, 256 MB RAM, a Creative SB PCI card, winamp with Jasper\'s Line IN Plugin and SS 1.31. I got a latency arround 500ms. How can I improve that ? What sound card do you think I sould use ? Is the PC strong enough? Please advise.

[jesseg]

using the software & hardware you have now, you could try:

(1) tweaking with the configuration on Jasper\'s line-in.  You can adjust the settings for the buffering that it\'s using.

(2) Switching over to Jasper\'s Low-latency waveOut plugin, but Jasper says you\'re not going to get much lower latency than using the stock DirectSound or MME output plugins.  I havn\'t really checked out how true that is, but hey it\'s worth a shot to try Jasper\'s output plugin.

As far as soundcards I will recommend, for any application, that\'s a VERY short list.  For an audio processor machine, I recommend RME soundcards above all others.  There is simply nothing else that has the same ammount of features AND anywhere near the same sound quality and performance.

Of their current products, I recommend checking out:
RME Fireface 400
RME Multiface II
of course if you have FireWire, i wouldn\'t hesitate to go with the Fireface series.  they are awsome interfaces.

[jesseg]

Well, I managed to get the latency of Winamp down to 2ms using ASIO input and ASIO output, but you\'ll need a soundcard with drivers that allow you to use multiple ASIO connections at once.  And also that allow for VERY small buffers.  I\'m talking less than 64 samples.  Most do not allow for this, thankfully RME does.  

Well, I also figured out the latency of SoundSolution2 itself.  It\'s 21ms when using BigBaw Killah v0.31 DAB preset.  That is already just a hair too large for realtime monitoring unfortunately.  So with no lookahead, SS2 & BBK v0.31 would have 17ms latency, plus the 2ms soundcard latency, puts us right at the 19ms \"limit\" for realtime monitoring.  Any more than that and the average human auditory system perceives it as a delay.

It may be possible to reduce the latency of SoundSolution2 more by disabling more stuff, but I didn\'t check to see.  In fact, if you enable the clippers and 15kHz filter, you may end up with more latency.

[Omnia6]

Interesting read......

Has anyone done any tests for the best Latency on SS1?

Would be good to see the difference between them both, would be an even fairer test if perhaps jesseg compared the 2 as it would be the same Sound cards and PC on both? (Hint!) LOL!

What Latency do Orbans/Omnias run at, is it around 17ms??

[jesseg]

Omnia6EXi current versions (and most Omnias of all flavors)...   9ms

Orban....
check this comparison grid, latency row
http://www.orban.com/products/radio/fm/feature_comp/
the 8500 actually has the lowest latency for any of their post-8200 digital processors.

[Omnia6]

That's interesting Jesse, does anyone know the lowest latency that anyone's ever got SS1.3 at is?

[jesseg]

The latest XAP, which is essentially SS v2.2, sounds better than SS2 "demo" in every way I can think of.  The latency will always be too high partly because it's a winamp plugin...  you can't integrate the plugin buffering directly into the soundcard access which is partly where the problem is.  But also it's by design (at least when it's running in Winamp) going to have another minimum delay of 576 samples.  It is possible to send plugins less samples per call to process those samples, but the plugin internally is also buffering the signal to avoid problems since that is variable.  As you found out @ 1024 samples, if that's the case.

But still, the delay mostly comes from SS/XAP's processing itself.  I don't know if anyone except Alessandro could answer questions about how the buffers were (or were not) optimized internally.


[edit]
oh i see what happened now, that's just a spam bot, lol...  pwnd?  haha.  damn i should get admin access here, cos this crap is so outdated and is going to get pwnt one of these days.
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