BrusFri Limitations iOS

21 June, 2019 10:10AM ยท 3 minute read

For several years I’ve been editing all of my podcasts on iOS using the wonderful Ferrite app. For a brief time I trialled Adobe Auditions noise remover and whilst it was excellent the switch to a subscription put it out of reach for me. Switching to Audacity for a time it wasn’t as good however it was passable. Moving to a full iOS workflow at that time was unfortunately not practical so I went without for quite a while.

Then listening to another podcast by Tim Chaten he mentioned the Klevgrand BrusFri audio plugin that was both an independent app for noise reduction in audio, but also an Audio Unit Extension meaning it would work perfectly within Ferrite.

I began using it and have been using it happily for just under a year now, although recently I found some inexplicable audio artefacts when it was used in Ferrite as a plugin. The noise blip lasted about 1/2 a second, and it was random. I did some research and found that I wasn’t alone - it appeared to be related to the bit depth, sample rate and also potentially the size of the raw audio file Ferrite was using. If you removed the plugin the audio was output correctly, hence it wasn’t a Ferrite problem, but appears to be an Audio Unit Extension integration bug in iOS12 which seems to have been present from that release.

No problem, BrusFri is also an independent app that can be used to import, reduce noise and export the result. Adding this step to the workflow solved the problem and also significantly reduced the Ferrite processing time when exporting the final audio. The noise reducer for 1 hour of raw audio takes about 8 minutes to process in Klevgrand on an iPad Pro 2nd Gen 12.9".

So far so good, however earlier this year I started to record some longer episodes of Pragmatic. When importing the audio into BrusFri it would spontaneously crash and once it did, attempting to reopen the program would result in an instant crash. The only way to recover from this was to completely delete BrusFri from the device, download and reinstall it again. At this point I began to investigate the app itself and found many others had exactly the same problem.

Not wishing to give up on my amazing noise reducer I iteratively changed every parameter I could think of when pre-converting the raw audio in an attempt to empirically determine the cause of the crash. The aforementioned reinstallation process became somewhat tiring after the 25th time or so.

Turns out the problem stemmed from the length of the audio, not the format. The longest raw audio file I am currently able to import to v1.1.0 of BrusFri is 1hr 40mins. I’ve been working predominantly in WAV but I tried a few other formats and they all appear to work fine provided they’re less than that duration. So for any podcasts that I record, if I want to use non-glitchy noise reduction on the iPad then I need to split the audio into pieces not greater than 1hr 40mins.

Ordinarily I’d throw my hands up in the air and start using my Macbook Pro for noise reduction via Audacity, but it’s not as good as BrusFri and I’ve already paid for BrusFri and it does an amazing job! I’ve contacted the developer however have yet to hear back. Given that the last update to the Noise Reducer was over 1 year ago, I do not hold out much hope for a quick response. I’ll keep you posted.