Jump to content


Please note: You can easily log in to MPN using your Facebook account!

Low latency audio interface for playing vsti's live


Recommended Posts

I did do some optimization on the settings, it was from a page on the Focusrite site https://support.focusrite.com/hc/en-gb/articles/207355205-Optimising-your-PC-for-Audio-on-Windows-10

 

I didn't look at the Cantabile guide yet but I'm guessing they cover the same tweaks.

 

I did a couple more tests:

 

Recorded into Zoom multitrack recorder:

 

Direct audio from Roland sound module vs. SM58 on keystrike audio = Roland audio average 16 ms behind

Direct audio from laptop vs SM58 on keystrike audio = Laptop audio average 30 ms behind

 

This means on the Roland it's about 16 ms latency which is MIDI latency plus whatever additional processing time. ?

Not sure why the difference between the laptop and the Roland was 14 ms in this test, when it was 6-7 ms in the other test. Different test method with different factors I guess?

 

Either way, would these numbers be considered normal?

I just have a generic MIDI to USB cable going into the laptop. Is there a better way? Is there MIDI to USB-C? What interface can I use to improve this latency?

 

I would not consider that normal. 30 ms is high and definitely in the range that I think most would notice. The cables are not the issue, midi involves the transfer of a small number of bits which USB can handle just fine. Similarly virtually all audio interfaces are USB 2 and perform well with low latency. The issue lies with drivers, hardware, or settings on your machine. There are a number of good guides on how to configure a PC for best audio performance. . For example are you running max power mode?

 

There is a good guide available on the Cantabile site see this link Glitch Free

 

Suitcase 73 - D6 - Poly 800 - ATC-1 - Motif Rack - XV-2020 - plug-ins

Link to comment
Share on other sites



  • Replies 33
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Tusker makes a good point about getting an audio interface. The benefits are it comes with an optimised audio driver, you shift audio processing off the laptop and most have master knob to alter volume on the fly. I use a 2nd Gen Focusrite. Around $120 when I got mine. Sure RME' are the Rolls Royce, but 5 or more times the expense for one way improvement of 2ms or so. You are searching for a 15 to 20ms improvement which, if audio is the issue here, any interface will fix.

 

Oh okay, what you guys are saying now is more reassuring. I think someone said earlier in the thread that they didn't think a good interface would improve things much. Of course I am hoping it will! There is a used RME Babyface on eBay for $280. Good deal, right? The Audient id14 is also interesting. The Focusrites look like a popular cheaper option. Do you guys know much about the Zoom UAC-2? Supposed to be very low latency, but I'm seeing reports of it failing on people. Any others out there that people like?

Suitcase 73 - D6 - Poly 800 - ATC-1 - Motif Rack - XV-2020 - plug-ins

Link to comment
Share on other sites

The question is: what is the actual chain of connectivity and the actual signal path of the midi and the audio that's going to take place, in this highly pipelined and virtual memory system fitted multi tasking machine we call PC, be it Linux Mac or Windows, but presumably with an Intel or Amd processor. I can get 1 (!) sample delay on my self designed and built DSP analog emulation machine from around '04, I know that's fun and holds some interest. I can take my Zynq FPGA board with Linux and seriously fast programmable logic and run interaction with hardware signals responding at 1/1000th (a thousandth) the time of a 96kHz sample, and depending on the computations required probably at one sample latency at 96kHz or even a MHz sampling frequency. That's interesting me, but it's far from how you'll get the modern PC hardware and especially Windows software to respond to input, and create samples. When the OS doesn't need much CPU time, and you're a low level programmer, you should be able to get some Midi and basic computations done if you can lock yourself in an interrupt routine or even to a dedicated thread processor (I'm not sure Windows normally allows this) in like a microsecond, because running at 3+GHz, that's enough to execute at least hundreds of machine instructions, and do some memory access requiring changing of dram pages and passing through some virtual memory queues.

 

Kernels can run 1 microsecond interrupts, which should be a very good latency. But you need to get your (usb) midi signal in the machine through some microprocessor in the Usb hub, which works a certain (not all too direct) way. Filling your sound card buffer should be possible in a short time, if no other processors get hold of that resource first, but there's memory management possibly in the way, which can cause extra latency, depending. Then, the actual "work" you plugin needs to do, apart from all kinds of indirect addressing structures for code and data which cause potential delay, could be access to a drive device, which has it's own string of unpredictable possible delays, and maybe the computations need to go through the floating point pipeline, which has a certain minimum flow-in flow-out time as pipelined piece of the CPU architecture.

 

With a well set up PC and a simple plugin, this all might work pretty fast in certain cases, no other programs ope, updates off, restarting often, but you might not get as low anyway because of the whole architecture and choosing parts maybe 30% faster here and there isn't going to get your latency in the milliseconds range easily. Also, for instance when you try to interpret you Task Window, normally the whole computer during playing a VST will probably be very close to idle, because it's dealing with an architecture that wasn't really primarily created for this, but for longer types of computations. Those computations which coudld make a (probably high latency) plugin demand some actual serious CPU usage of say at least 40% are then in the supercomputer real estate on the Intel or Amd chip, where normally you don't get and where interactions simply aren't very real time.

 

No interface changes those basics. Maybe a card like the early Soundblasters with hardware accelerated wave tables help some, or an actual DSP card which almost independent of the CPU get's stuff computed, or can pre-stream samples in hardware can help, but generally there's too many eventualities in a modern PC to get reliable short response real time behavior, I'm afraid. Not that you can't run a bunch of VST's, I sure could, but those reliable fixed and short latencies are simply hard, not so much depending on the interface. Maybe it's possible to make card (with none of the serialized IO connectors like Usb Firewire or Thunderbolt) with OS additions that gives fairly good latency and couple that with smart programming of plugins, but I don't know good examples of that, so it's a compromise.

 

T

Link to comment
Share on other sites

....

DAWbench Radio Show :

 

Episode 03: Audio Interface Low Latency Performance : RME â Setting the Bar !

 

Special Guest : Matthias Carstens

...

 

 

Listening to the first part of the show it's interesting hoe the FPGA development Rme did was essential to their success I didn't know that. I recently revived my Zynq board to work with the latest Xilinx tools, and amworking on some Aws cloud computers for using fpga's there, which is however not about the low latency DAW audio problems, primarily. Though I could imagine an edge device working with a cloud node to do audio reproduction.

 

T

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...