UV#07 What is JACK Audio Connection Kit?

Hey, here is Unfa, you are watching Unfa Vlog, I will talk about JACK audio connection kit in the future. There are important things around it. So, if you just entered the Linux audio world, you may have heard of JACK. And it’s everywhere, but what is it? What is JACK? Jack is an audio system that allows independent programmers to work together on audio If you are used to using a digital workstation You know that he has a mixer, a sequencer has a sound (Fx) slot, etc. With JACK, your entire system is like a huge DAW so that everything can work together This is a very useful tool And I can’t imagine how I can’t plug or unplug these virtual wires. What should I do? With Jack, you can also turn your Linux machine into a LIVE music show workstation.

Can use a variety of software synthesizers, Midi processors, effects tracks, loop loop phrase workstations, samplers and all the great stuff Not everything can be achieved through plugins Sometimes you need an independent program Because of JACK, there is no technical limit. a little technical stuff So, Jack is a sound system that works on a server type, so you can keep it in sync. The program connected to the server is called the JACK client. The server passes the data around, ensuring that each program gets what it needs, and the sound is processed. JACK itself is an extremely fast and trustworthy thing A famous product like MOD Duo proves its ability This machine is running an embedded Linux system with JACK Is a versatile, highly adjustable rhythm instrument and multi-function instrument integrated effects Can be used on the stage or in the studio If you are interested, you can visit their official website. Basic JACK setting Let’s take a look at the basic JACK server settings. A front-end tool that can set it up is called QjackCtl Is this program I will use it to demonstrate how to set up JACK So let’s make settings Press the ‘Setup’ button, the first thing to do Is to choose your recording interface Very convenient, it appears on the first tab you opened Then we have a list here Only the interface with MIDI interface is shown here.

But of course, but using them will not give you any audio features. However, the device I am currently using is booted from Cadence (another JACK setting software). So it doesn’t matter If you use a built-in PCI sound chip or an external USB recording interface You will need ALSA driver But if you are using the firewire recording interface You will need to choose a different driver There are some different ones, such as net and net one Can allow multiple computers to connect together through the network to handle sound But this is another topic that is completely different.

Buffer Once we choose the driving method and device, we should pay attention to the buffer The buffer determines the amount of audio data that the JACK server and client can process “once”. The larger the buffer, the more time between each buffer operation Therefore, just passing the buffer will leave “overhead” It takes more time to process the sound Buffer large = low CPU usage If your CPU performance is low, the bigger the buffer, the better. On the other hand, the larger the buffer, the higher the latency of the audio. This means that the time from when you input the command until the sound is processed, and then the sound will take longer. When you set too many buffers You won’t be able to play a guitar with an instant effect or play a synthesizer Because you always hear the sound coming late after you finish playing.

This is really bad Large buffer = high latency But you set the buffer too small Your DSP (audio signal processing) may burst to 100% Then you will hear “Xrun” Xruns Xrun is a situation where your CPU can’t handle the audio buffer instantly. The sound will be incoherently heard (pop), click (click) sounds like a malfunctioning sound, generally very broken JACK server measures the number of Xrun And also measure how close you are to Xrun To overdo your system Here we can see that our DSP load is 8% And dSP is now processing, is the voice of my speech Behind the use of a large ticket plugin If the DSP load is close to 100%, then you are in danger zone and the sound may be “rotten” However, you still have the possibility to get your DSP load monitor out of a lot of That’s it – you set the buffer to a low to ridiculous value, such as 32 samples or lower what should you do? Just try to set the JACK buffer a bit larger. Here, Frame/Period (a period of “several”), this is the basic value I usually set between 256~1024 Then there is Period/Buffer (buffer contains several periods), this will be multiplied with the above If you have 4, the buffer will become twice as large as the default, but I usually only set it to 2 If you need low latency and can’t use a larger buffer, then you might want to try to reduce the load on some operations.

For example, you only use two layers of compressors instead of stacking eight Finally, you can consider upgrading your hardware and providing yourself with more CPU power. But there is one more thing to try before doing this, I will take a minute to say it by the way. The higher the sampling frequency, the shorter the delay of the same buffer setting why? Because you have more samples in a single second, so the same number of samples, the buffer needs to process them more quickly. I usually use 48000hz, but this is just a personal preference. I know a lot of people use 44100hz Here is the place to set the sampling frequency, yeah~ There may be a ton of things that will affect your JACK performance.

If your performance is really bad, it may be that your system is not properly tuned. Evaluate your computer with the LIVE boot disk system So the quick way to do this is to try liveCD Many professional music production departments have Linux distributions available Live DVD such as AV Linux or KX Studio These complete GNU/Llinux systems are specially prepared to give Jack a great performance.

Then you can put them on the flash drive and take a look at your computer to see how it works. You may need to check out the UV 0-5 episodes of my past videos, mentioning about KX Studio and installing it on a USB flash drive. Instant mode JACK has a setting called “Realtime scheduling” It is in this place, it is the display light marked “RT” “Jack server mode”, it is in immediate scheduling In the settings, there is a checkbox labeled ‘realtime’ (instant) So, what is its role? It enables the Jack server to use higher priority permissions in the system.

So, it can get the job done before the deadline, which means it can process the audio instantly without “dropping” However, for this kind of work, you will need a special Linux kernel. Generic Kernel (common core) included in most Linux distributions like Ubuntu and Linux Mint does not support this So what we need is “low latency Kernel” You can search for “Linux-low latency” in the suite management program.

Then you will find the complete low latency Linux core list If you install this, your system will use it the next time you turn it on. But ~ I remind you in advance that switching the core may make the system boot up. So, make sure you know what you are doing so that you don’t want to reboot after the black screen welcomes you. But fortunately, this is safe, most of the time. JACK transmission “Jack Transport” is a feature that allows different programs to play simultaneously I use this, for example, recording guitar and vocals in Ardour and drumming in Hydrogen drum machine software.

Or when I make animations in Blender and make movie clips with Blender I can edit audio simultaneously in Ardour I can even use the “Jack Transport” to sync the timeline so that all programs can be played together, which makes all the programs seem to merge! This is very helpful and it feels like it’s getting everything together.

QJackCtl control Let’s take a look at the main control panel of QJackCtl Here is the control button for “Jack Transport” I can click here to start “transfer” You can see that it is running (rolling) Then the current transfer position is spinning I can suspend I can roll back and start Or fast turn One second forward, one second backward So regarding the control of ‘transport’,

We now have a main display We can see that the Jack server is up, running, using instant scheduling, DSP load is about 10% The sampling frequency of playback is 48000hz No Xruns have happened yet Transport is stopped, parked at 0 Jack Transport also sent information about BPM (several quarter notes per minute) So if my Ardour and Hydrogen are synchronized together If I change the tempo of the Ardour software, the speed of the Hydrogen software will change.

This “connect” and “Patch Bay” can be used as a connection. “Connect” is a manual thing You can see that my system now has some connections These are different effects They are managed by Carla, which are the latter You can see my vocals being processed here And the OBS (live/video software) Jack input is here. This is how my film is recorded.

We also have MIDI Can handle the connection of Jack MIDI and Alsa’s Alsa MIDI Because there are two kinds of MIDI mechanisms (the translation of ALSA is the lower the theoretical level of the hardware hierarchy, and the convenience of Jack is the connection, each has its own strength) “Patch Bay” is similar to But you can create “presets” (preload settings) Define name Then store When a client program with a specific name appears, Jack Patch Bay will automatically reply to them.

So this is a very useful thing, for example… There is a hardware setting, you want to have the corresponding software settings, you want to be able to connect the software and hardware in a specific way, then you can start working In addition, in this “setup” you can also set this:

In the ‘misc’ tab, there is this option “Automatically bring up the Jack server when the program starts.” In this way, when you start QJackctl, the Jack server starts automatically. And you can also use your system’s automatic startup mechanism such as cron, not crontab You can use the system’s automatic startup mechanism to let QjackCtl start automatically. However, in the past I used these hacks, but I don’t need to use KXstudio now. Because everything is fully automatic. Finally, the “Start” and “Stop” buttons are used to start and kill the Jack server.

Only when you have to make major changes to the Jack server You need to use them For example, you have to switch hardware devices You have to stop the Jack server Then go to the settings area to make adjustments Change the recording interface to be used (Audio Interface) Click “ok” and then start, then see it running But this did not try to change the buffer size Click on ‘ok’

Then start again Troubleshooting If you tried it many times, you can’t let Jack execute it. You have to check something and see where the problem is: First, make sure that no other audio related programs are working. This includes a web browser, And the Pulsesadio audio server And any program that can play and record sounds. Because it can take up the sound hardware and Jack can’t control it.

I used to use plain text commands in the past: Sudo alsa force-reload What I want to do is to reload all the core modules and drivers related to Alsa (if I am wrong, please correct me) He will force all programs that use them to close So when the sound hardware is occupied by a program, it dies.

However, sometimes this does not necessarily solve my problem. So when things change in substance, I still do this, maybe the system will “explode” The second one to check: Does your sound card supports a specific sampling frequency and buffer size? Because I have seen Jack refuses to start the sound card. Because you don’t accept buffers that are too small or too large T

his time, if you want to know more about Jack, please visit its website. Over there, you can also find a list of very interesting programs that you can taste early. You can have fun with them Thanks for watching Have any questions or have any suggestions for my future shows Please leave a message below, we will meet again in the next video~ Bye~~~ Wait a minute, there are extra things, listen to it. Song Lyrics: What is Jack~ Baby, connect me~ Contact me~ Come again~ What is Jack~ Baby, connect me~ Contact me~ Come again~ NG fragment biting the screw

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