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Old 02-23-2020, 07:41 PM   #1
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Join Date: Nov 2007
Location: Winnipeg, Manitoba, Canada
Posts: 9
Default Reaper audio playback glitching when limiter placed on sub-master bus

I recently isolated a persistent audio glitching issue that I have been experiencing over the last year during playback on Reaper projects.

I use Reaper for audio post production. During my re-recording mixes on a number of TV series, I noted that Reaper was experiencing buffer-style playback glitches as I neared the end of my mix of each episode. The Reaper Performance Meter has always reported relatively minor CPU usage (<25%), so I was quite confused.

On my last mix I began experiencing the same issue, but luckily I noticed that the issue ceased when I disabled a limiter on a bus within the project. The bus in question I label: sub-master. I use it like a master bus for all audio in my project (i.e. dialog, Foley/SFX, score, soundtrack, etc.) with the exception of a track containing the -20 dBfs reference tone and the 2-pop, which need to pass through to the actual master bus unprocessed by plugins that reside on my sub-master.

My sub master contains a compressor followed by a limiter and then finally a gain plug-in. The limiter that I typically use is the Waves L3-LL Ultra Stereo limiter. When this limiter is active on the sub-master, I experience audio playback glitching. When I disable the limiter, the glitching ceases and audio playback is error-free. While troubleshooting I also swapped-out the Waves limiter for other limiters by Izotope and Slate Digital. Once again, each time one of these limiters was active, I experienced audio playback glitching.

Next, I tried moving the sub-master plug-in chain to the actual Reaper master track and experienced no audio playback issues. On a hunch, I replaced all busses in my project with folder tracks (but an otherwise identical routing structure) and the audio playback glitching ceased. I can use a limiter on a folder track sub-master with no issues whatsoever.

So it appears that the playback issue is specific to a buffering issue when a limiter is placed on the sub-master. Using folder tracks is an acceptable workaround for me, but I wanted to report this behaviour as is certainly seems unusual, creating an almost unworkable situation if one needs to process all audio in a project through a single bus prior to the master bus. I'm pretty sure it is a bug.

I look forward to any responses/insight.


MacBook Pro (15-inch, 2018)
Processor: 2.9 GHz Intel Core i9
Memory: 32 GB 2400 MHz DDR4
Storage: 1 TB APPLE SSD
Graphics: Radeon Pro Vega 16 4080 MB
Intel UHD Graphics 630 1536 MB
macOS Mojave 10.14.6


Length: 44:32.704
Video: 1920x1080@23.98fps, Aspect=1.00, Decoding format=RGB

Using VLC decoder (v3.0.x)
Video: 1920x1080, h264, 23.98fps

48 kHz, 24-bit

I am using REAPER 6.04/64
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