I want to move to an all digital audio playback setup, I will not be making and recordng any music.
So does low-latency audio have any relevance to me? Will using a RT kernel and associated system tuning make any audible difference over a bog-standard ALSA setup?
I don't know if I should bother to pick a more specialized Linux distro or not.
I'll be using a ESI juli@ s/card via optical Spdif into an external DAC.
low latency audio questions
Moderators: MattKingUSA, khz
-
brummer
Re: low latency audio questions
No, as long you didn't drive your system to the limits there will be no benefit.
The benefit of a rt-kernel is, that you could fine tweak your system to priori tasks witch important for you and delay tasks witch are not so relevant for now, for the Real Time.
But why do you ask, is there anything in your system witch didn't work like you wont ? Or just for information ?
The benefit of a rt-kernel is, that you could fine tweak your system to priori tasks witch important for you and delay tasks witch are not so relevant for now, for the Real Time.
But why do you ask, is there anything in your system witch didn't work like you wont ? Or just for information ?
Re: low latency audio questions
I asked as there are (linux) computer audio sites that imply there are benefits in using RT kernels and thread/irq tuning for audio playback. And if there was, it would partly determine which Linux distro to use, eg. AV Linux or something like VoyageMPD, depending on the target hardware. And I'd have to put some effort into how to do this type of system tuning. But, if the benefits are not tangible, then I can forget about it.
Actually as a test, I think it might be as simple as using a Linux distro that has the latest preempt kernel, boot with the "threadirqs" option and with rtirq-init installed which is what AV linux does. Otherwise it would meaning using the latest RT kernel available.
Anyway, if informed opinion is that low-latency audio is of little value for audio playback alone, I can focus on other parts of the audio chain.
Thanks for your reply.
Actually as a test, I think it might be as simple as using a Linux distro that has the latest preempt kernel, boot with the "threadirqs" option and with rtirq-init installed which is what AV linux does. Otherwise it would meaning using the latest RT kernel available.
Anyway, if informed opinion is that low-latency audio is of little value for audio playback alone, I can focus on other parts of the audio chain.
Thanks for your reply.
Re: low latency audio questions
for audio playback only, low latency is totally irrelevant. However, you misunderstand what RT is: it is "100% deterministic process time of a given thread work". So, given this definition, you can very well have a process thread that takes a very long time to complete its work once the CPU is busy with it. If the thread is RT, it will complete within a very precise time limit without any chance of being bullied by some other processes (non-RT) unless some other RT thread with a higher priority comes into the picture.
Low latency in our "audio world" is as small as possible process time between what you inject to the PC and what you get out of it after processing (very crude definition). You can have a very small latency for audio processing but if the processing thread is non-RT, chances are it will be bullied by something else. A glitch-free experience is therefore highly unlikely. If the audio thread is RT, then it will be less likely to happen. But low latency is only needed if you play s/w instruments (so you do not feel the delay between your human action and the PC response) or for realtime audio effects (same argument).
Low latency in our "audio world" is as small as possible process time between what you inject to the PC and what you get out of it after processing (very crude definition). You can have a very small latency for audio processing but if the processing thread is non-RT, chances are it will be bullied by something else. A glitch-free experience is therefore highly unlikely. If the audio thread is RT, then it will be less likely to happen. But low latency is only needed if you play s/w instruments (so you do not feel the delay between your human action and the PC response) or for realtime audio effects (same argument).
Re: low latency audio questions
Low latency in itself is only really needed when you'll have output and input at the same time and they need to be related. Like when you record a track while playing back a previous take, or when you play a software synth. If all you'll be doing is one or the other then it isn't important. Maybe when you playback video you don't want the sound to come much later.
In this case you might not even need a preempt kernel. Depends a bit on your pc and the workload. But it has been a very long time that I have seen xruns when just doing some playback.
In this case you might not even need a preempt kernel. Depends a bit on your pc and the workload. But it has been a very long time that I have seen xruns when just doing some playback.