Playback juddery

SteveCherelle

Hi. Had the app 10 years.
Since the last update when songs playback that I have adjusted speed or key with within the app are playing juddery and bitty. I’ve checked with a new track that’s fine, imported and fine, sped up a tiny amount and the sound is awful.
Never had this. It’s as though the speed and pitch features are now very poor. Must be a conflict somewhere. If I take the speed back down it’s fine. These tracks have played fine with adjustments for years with th app but not now. I’m using latest iPad mini

Thanks
Steve

SteveCherelle

Ps Peter.
I updated my device to iOS 16.1 yesterday and so it may be that.
There was a st update too so it could be either or a conflict somewhere.

I was on ios 15.

peter

I didn't notice any playback issues with the current version with tempo changes. No matter whether on iOS15 or 16. What is your exact setup (iPad or iPhone version, file format used, sample rate, external audio interface)?

SteveCherelle

Hi Peter.

Today I have done some investigating.
I have new iPad mini.
Worked fine with songs with tempo or key changes, until I updated to iOS 16.1.
I used for a year with no issue until I updated iOS and then the songs sign adjustments play poorly. If I slow them back down the issue goes.
I have loaded the full database back up to an older iPad using iOS 12 and it’s fine with no issues.
I’ve also loaded it to my iPhone 14 with iOS 16.1 and it has the same jumpy issue.
So that shows me it’s an issue with iOS 16. Or iOS 16.1 and seems to be with just the tempo changes tracks.

All songs play fine but those that have had a tempo change within the app are judery, sound is bitty. It’s only with songs that I change tempo on.

Steve

peter

What format are your files in? Mp3? Which bitrate?

I don't see this issue on an iPhone 11 with iOS 16.1. Speeding up/down and changing the pitch does not have any unusual artifacts.

SteveCherelle

Hi.
I have a mix of mp3 and wavs.

Peter.
For years it’s all been ok. Every change on any type track.
But with iOS 16.1 the tempo changes tracks are not useable. This is the case on iPhone 14 or iPad mini. New model.

It’s does not do this on iOS 15 or below. That’s what I have worked out.
I can’t roll back iOS updates and so the machine I use I can’t use now and am back on very old iPads.

It’s a software glitch somewhere.
I can email you a video if you give me an address. You will see and hear it then?

Steve.cherelle@yahoo.co.uk

We will work it out I know.

peter

Please send it to support@stagetraxx.com.

And before you do that, please try to increase the audio buffer size in Playback Settings. Maybe this will help

SteveCherelle

Hi. I did that. Just tried again on them all. It’s very odd. Same data base plays fine on any iOS but 16.1.

I have 4 machines now all doing the same issue but not when it’s on the pre iOS 16.

How do I send you a video?

peter

Just email it if it is small (below 20mb). If it is too large, you will need to upload it to a file hoster and send me the share link.

peter

I've tried to reproduce this on both iPhone and iPad running with iOS 16 and I do not see this issue.

Is anyone else experiencing these kind of problems?

MasterAnt

I can confirm this!

Just tested this using three devices:

iPad Pro 2021 iPadOS 16.1
iPhone 14 PRO iOS 16.1
iPad Air 2 i?OS 15.7 (my live gig iPad)

I only tested one song. Any pitch or speed change using 1. or 2. produces wobbly sound, especially audible on bass guitar which is now no longer smooth on long notes.

I have an iPhone 8, but haven't upgraded it to 16.1 yet. Am reluctant to do this for testing, as this is my primary backup player at gigs.

I'll fiddle around more and see if I can come up with anything.

SteveCherelle

MasterAnt
Thanks.
Me and Peter are trying to work it out and so this confirms it’s a glitch somewhere. Best not to update anything for now.
I can’t roll back to 15.

Let’s see what Peter thinks.

MasterAnt

Testing observations so far:

No difference made using any of the four buffer sizes.
Nothing else is set on the track: no eq, fades, volume changes.
Source file is mp3. All my files are compressed the same:
Size: 4493692 bytes
Header found at: 6563 bytes
Length: 186 seconds
MPEG 1.0 layer 3
192kbit, 7167 frames
44100Hz Joint Stereo
CRCs: No
Copyrighted: No
Original: No
Emphasis: None
Not running any master EQ, except for a +6dB volume gain.
Occurs on both bluetooth audio and internal speaker
Occurs in all players: song, edit audio regions, playback & trim
Occurs on all songs I've tested. Less audible on some.
The wobbliness sounds similar to WinAmp + XFX's pitch shifter from the early 2000s, ie. a very early algorithm which had echo artifacts, etc.

Seems like an issue between the algorithm, iOS 16, and the CPU architecture

SteveCherelle

MasterAnt
Thanks for the further testing.
Your description is spot on and so thank you.
I have a back up old iPad for now.
Will leave the new one until we find a solution. It’s a strange one eh.

peter

OK, now that I know what to look for I can hear a difference in the bass between iOS16 and prior versions. It seems that Apple has changed the algorithm in the audio unit that Stage Traxx uses to change speed and pitch. And this change is not for the better. I have compared the sound of iOS pre 16 and macOS Monterey and they both sound the same. Not sure about macOS Ventura as I have not yet upgraded.

Unfortunately there is nothing I can change in the way this audio unit works. I will open a bug ticket with Apple but that can take a lot of time if they react at all. Replacing the audio unit with a custom built is no really an option as I have not the necessary math knowledge and most developers use the stock audio units.

So bottom line: we will be stuck with this until Apple reacts to the bug report.

SteveCherelle

Hi Peter.

Thanks for that reply.
It makes my new machines obsolete and apple may never change it. It’s a pain eh but not your fault. Hopefully the ticket may help.

Perhaps advice users to not do the updates. If ya use those features then back track singers will be stuffed at the gig after they update. I was.

I will awaits any updates. Thanks for always being on hand for advice Peter.

Steve

peter

I found a mention about something similar on the Apple developer forum. Seems like the algorithms Apple uses are hidden from direct access but there is a trick to force the use of a specific algorithm. Through trial and error I found the algorithm that was used in iOS prior to 16 (at least seems like it to my ear). And this dirty hack seems to work (at the moment at least). This hack will be released in version 3.6.3.

SteveCherelle

peter
Legend. Glad it’s raised and can help fellow acts now Peter.

MasterAnt

@peter Nice work finding a hack!! Nothing's more frustrating than being at the mercy of these big corporates.

MasterAnt

Just wanted to acknowledge @peter and @apple that this algorithm is famazing!!! I've never used live speed changes until very recently in ST3—have always remixed my tracks in Logic for different tempos. I still don't use live pitch changes, but I know that I could if necessary.