Support Lower Latency Setting of Audio Interfaces

[soundboyrich]

Feature Description

First of all Mixxx 2.5.4 improvements with DVS is a blessing. Thank You. Let's take the responsiveness of Mixxx further by including lower latency setting of the software beyond the 96KHz sample rate and 1.3ms Audio Buffer setting in the ASIO Preferences. Mixxx is getting closer to "feeling" like vinyl but is not there yet. I need software that "feels" like vinyl to beat match, cue, scratch all the things that DJ do while never missing a beat. Latency has crept into software, Mixxx needs to keep lowering latency.

I used a software utility RTL (Round Trip Latency Utility) which gives me the loop-back time of the audio signal output-input. With the Mixxx setting of 96KHz, 1.3ms the RTL is 2.865msec (~ 1.3ms X 2) but my audio interface with a fast CPU can support even faster, i.e. lower latency, settings.

Here's results from my Lynx Audio E44 audio interface
Sample Rate Audio Buffer size (msec) RTL(msec)
96KHz 128 Samples (1.3ms) 2.865
96KHz 64 Samples (0.7ms) 1.531
96KHz 32 Samples (0.3ms) 0.865

192kHz 256 Samples (1.3ms) 2.755
192kHz 128 Samples (0.7ms) 1.422
192kHz 64 Samples (0.3ms) 0.755
192kHz 32 Samples (0.2ms) 0.422

Btw, I was able to use DJ software with settings below 1ms but this other software (VDJ) is full of bugs when it comes to DVS.

A desktop CPU, e.g. Ryzen 7800 X3D, I'm able to easily go beyond the 96KHz 1.3msec setting of Mixxx.

[daschuer]

There is nothing in Mixxx that prevents us enabling a lower latency. However I am in doubt that it is an issue of the audio latency you feel. It is probably the control latency.
The related code is DlgPrefSound::updateAudioBufferSizes()

[soundboyrich]

When I move the pitch control on a Technics MKIII analog turntable to beat match the DJ software can't keep up. I don't use CD player decks, digital controls or other knobs/button. When I switch over to vinyl by passing the audio interface it is no comparison. I don't have time to dig into the software to change the code so I'll wait for the next update when a change is implemented.

Too much electronic music is what I call metronome music. It's a single bpm from start to finish. Fortunately live instrument playing recorded songs aren't metronome music, tempo change all throughout the song. I play a lot of this music still.

[JoergAtGithub]

Could you try out our 2.7 alpha builds? 2.7 has some significant improvements for DVS responsiveness.

[soundboyrich]

Thanks for the tip. I'll see if I can pull a copy in a few days. Never used GitHub but I've used Git and Git GUI.

[JoergAtGithub]

You can download the 2.7 Installer either from GitHub or from our download server which is linked on our homepage.

[soundboyrich]

I do not see a link anywhere to download 2.7 Installer on GitHub. I'm at my Dashboard on GitHub. I see instructions for source and building using VS 2022. I see 2.6 Beta on Mixxx website.

[Eve00000]

for 2.7 scroll down to "Development Snapshots" on https://mixxx.org/download/

[soundboyrich]

Thanks, found 2.7 alpha on your link

[soundboyrich]

Version Alpha 2.7, Vinyl Control Tab, Lead-In Time out of the box is 10s for Traktor MK2. Something I usually overlooked this parameter but checked after I notice dropping the needle anywhere near start the vinyl immediately begin play the media (at start point). I set Lead-In Time to 1 second, used Traktor MK2.

I then switch the vinyl to Serato Vinyl Side A, Lead-time comes up 28s, I switch that to 1 second. Cue the vinyl at beginning was impossible. I switch back to 28 seconds and cue at beginning OK.

OK, so maybe those seconds Lead-Time is not really "seconds" units, likely a smaller unit of time I need to extend to play a media beginning.

Please someone implement the higher Sample Rate and shorter buffer sizes so I can lower latency further. I could probably dig into the code myself but I have too many projects going on.

[soundboyrich]

Lead-Time of 11 seconds works best with Traktor MK2 vinyl. A needle drop at beginning of vinyl gives me roughly 2-3 seconds before track plays.

[soundboyrich]

There is nothing in Mixxx that prevents us enabling a lower latency. However I am in doubt that it is an issue of the audio latency you feel. It is probably the control latency. The related code is DlgPrefSound::updateAudioBufferSizes()

I pulled a copy of Mixxx, Windows 10 PC and Visual Studio 2022. Do I use VS to open a project file? I don't see a VS project file since this is multi-platform I get it is not used in this case. What hi-level file do I open to begin to make the changes to the section of Mixxx code you describe for the purpose of further lower latency settings

[tuulikauri]

What hi-level file do I open

Hey there! There's no "project file" and actually you cannot create a VS solution / project from the Mixxx code, I'm not sure why but VS2022 cannot build the project if you do (its a quite large and sophisticated build process). You simply open the top level repo folder; File->Open->Folder and VS should detect the CMakeLists.txt file and know its a cmake folder. The folder will show under your File->Recent Projects and Solutions options (but without a *.sln or *.vcxproj extension)

Here's a few links.
https://github.com/mixxxdj/mixxx/wiki/Developer-Guide
https://github.com/mixxxdj/mixxx/wiki/Compiling-On-Windows
https://github.com/mixxxdj/mixxx/wiki/Visual%20Studio%20Community

It's probably better to join us on Zulip to get further general guidance. I can help you get VS builds going if those manuals leave any gaps, I just hesitate to go into more details in a Feature request thread.