Audio Clicks on Galaxy Nexus 7

[planet-h]

I'm ran a couple of tests on my nexus 7 2013 (also on Android 5.0.2), with the latest G-Stomper Studio full version 4.1.2, running at the overall defaults (AudioTrack at 40ms).

I've loaded the Demo Pattern Set from the demo folder "G-Stomper-4-Demo" and let the song run through while switching screens and twiddling around with stuff. I noticed very rare clicks in the realtime output, but that is due to the slightly outdated cpu of the nexus 7 2013. Don't forget that we're talking about an almost 2 year old device. Then I reduced the sample rate from 48000Hz to 32000Hz and they went away completely (with 44100Hz I still had some rare clicks).

Btw. This behavior just started with Android 5.0.1, I drove the same test on a nexus 7 2013 running on Android 4.4 with no clicks at all.

Also you should know, that these clicks will definitely not be in the audio exports. Exporting audio is not done in realtime and will be always absolutely free from any glitches, even on the slowest device with the highest export quality (it just takes longer). Think that's a relevant thing.

Please try running it at 32000Hz SampleRate with the overall default settings, and let me know if you notice the same behavior.

[SerrArris]

I tried reducing Sample Rate to 32000, then 22050, removing half of the sampler/synth tracks, setting synth voices to 3 etc. No effect at all. The clicks and glitches still remain. Therefore I am pretty sure this is not a CPU problem but the bug must have another source (I tried some overall android settings, too, seeing if they have effect, e.g. location, flight mode, ...). Still no improvement. Strange, strange. How can I support you in finding the root of the problem?

Best regards,
Markus

[planet-h]

Thank you for making these tests and your detailed feedback.
To be honest, I think the root of the problem is the Nexus 7 2013 paired with Android 5. I have 2 identical devices here, one on Android 5.0.2, one not updated to Android 5 (actually running on 4.4). With Android 4.4 there's not a single pop (with AudioTrack).
It is also definitely not a problem with Android 5 itself, since the Nexus 9 runs at 20 and 10ms without any problem.
I love the Nexus 7, and it's still one of my favorite devices, but it's also one of the buggiest thing I ever had in my hands. I'm pretty sure you know about the well known touchscreen issues with the n7 2013, which can drive you crazy, however, that has nothing to do with this..
The point is, that the G-Stomper Audio Engine does not produces the clicks, it's the nexus internal audio chain, which comes after the app passes the audio to the nexus internal post processing. You can verify that very easy. Export a full song as audio, and afterwards play the exported wav on the player of your choice. You'll see there are no clicks. As said, it's only on the real-time playback.
Btw, are you using the headphone jack as output? Or the internal speaker? It's just a minor difference, but usually the headphone jack produces better results, since the audio won't go through some ugly post processing (which is done for the cheap internal speakers).

The good is, that I have 2 nexus 7 here, so there could not be a better base to find a solution. I'll definitely go after it.
I'll do some deeper tests over the weekend, then we'll see.

[SerrArris]

Dear Andreas!

Thank you a lot for the work you are putting into this issue (and for G-Stomper, too, of course). I use the headphonse jacks, as I use the Nexus 7 to create musical ideas while going by train. And I spend a lot of hours on the train. What I am really liking about G-Stomper is the possibility to use it in a live situation - let's see how I can make use of it.

Best regards,
Markus

[planet-h]

Hi SerrArris
Sorry, it took a bit longer than expected. I did many tests using the Nexus 7 2013, with Android 4.4 as well as with 5.0.2, with old G-Stomper versions and with the latest. The results were always the same:

Android 5+ has clicks. The amount of clicks depends on the used audio system, OpenSL has more than AudioTrack, but both have them.
On my Nexus 7 device (Android 5.0.2), when using AudioTrack at default settings, the clicks are very rare, around one single tick per minute. Running on Android 4.4 with AudioTrack, there are no clicks at all.

I did also some research on the web regarding this problem and there are quite lot of reports on many different apps about the audio clicks. However, I won't give up on that, but I cannot give you a guarantee, if there'll be a proper solution. I'm not 100% sure about it yet, but the fact that the AudioTrack system produces clicks (and the clicks are not typical GC hiccups or stutters which are known from performance problems) looks like there's a problem in the system.

As you read above, the initial topic of this thread was a KitKat problem (in the Android internal resampling), but that was solved a long time ago. G-Stomper internally always runs at the systems native samplerate, independent on the samplerate you select. If the selected samplerate is different to the native one, then G-Stomper does the resampling by itself as the very last part of the audio process. That way the Android resampling is not applied anymore.

The problem you report (the clicks on Android 5+) is something new and completely different, and it only happens on Android 5+ and only on the Nexus 7 3013. For now, the only ready to use solution is to get back to KitKat. If I find a solution for Android 5+ I'll of course post it here.

[SerrArris]

Dear Andreas!

Then lets hope one of the future Android releases (5.1 is on the way) solves the issue. I'd really like to use GStomper (and I bet I will). Thank you for your efforts!

Best regards,
Markus

[planet-h]

Yes, I hope that too.
I'll keep an eye on that anyway.
I'll integrate the Samsung Pro Audio SDK soon, so there'll be a time frame for performance tuning and optimizations (for all, Samsung, OpenSL and AudioTrack).