Hello FMOD Team,
We’re working on a VR application in Unreal and use FMOD as our audio middleware plugin of choice - first of all thank you so much for the fantastic product you’ve created! It’s been a pleasure to work with. We’ve recently noticed that a specific FMOD event we’re trying to use in our app doesn’t sound the same compared to the FMOD Studio playback, and we’re trying to figure out what’s going on in this situation. The event sound has a weird distortion happening when we play it back in Unreal (even in the editor when the game isn’t even running, when we double click and play it in the Asset Browser). The event is stereo, 2D, and built in PCM format, though the issue seems to happen in Vorbis or FADPCM as well. Also, I recently tested this in an empty Unity project to see if this was an Unreal specific issue, and it’s happening in Unity as well.
Would you happen to have any insights into what could be causing this? Here’s a video that demonstrates the issue: by showing the event playback in FMOD Studio, followed by playing back the event in the FMOD Events window in the Unity project. In case it’s helpful, I also have the test FMOD project and Unity project I was using to reproduce this issue here. The FMOD project contains the kick drum audio files that we’re observing this issue with. It seems to be a product of our sounds with some of the effects we’re adding in FMOD Studio that leads to this, but I would have still thought that the difference between what we hear in the game engine editor and FMOD Studio wouldn’t be this significant. Especially if we build the bank as PCM - I would have thought the differences would be minor. We’re on Studio and FMOD plugin version 2.00.05, and the Unity project is running on Unity 2019.2.6, though there’s nothing in the project except for the FMOD plugin and built bank. We observed this in UE4.21 and 4.23 originally. Any help would be appreciated as we’ve been trying to figure this out for the past week - thank you so much!
Just a minor bump - I was wondering if anyone was able to check out the video I linked to and had any ideas on what might be going on. Any suggestions or insights would be highly appreciated, thanks!
This does appear to be a bug of some sort, we haven’t been able to pinpoint the exact cause just yet.
Although we think the distortion effect may be due to the two EQs - if you crank up the gain on B & D on the first EQ and E on the second EQ you can get a similar sounding distortion playing back in auditioning.
I have raised this as a task as we will need to investigate this further.
Thanks for the reply, feel free to let me know if I can help by testing any possible fixes or workarounds!
Just as a follow-up to this, I recently did a test where I recorded the (undistorted) audio I was hearing out of the FMOD Studio playback in Audacity, exported that and put it in a new FMOD Event in the same project that had no effects applied to it in Studio. So when playing this back in Studio, it effectively sounded the same as the other event which had the effects applied to it.
When I built my bank and played back the event in Unity/Unreal, I heard distortion in the event with the effects as usual, but I actually didn’t hear any distortion with the event I had recorded in Audacity. Given the results from that test, it seems like some combination of the effects in the chain result in the distortion when combined with these specific audio files. Even though lowering the gains on the EQs helps get rid of it somewhat, I was still hearing the distortion just with the limiters enabled and boosting the input signal. Feel free to let me know if there’s anything else I could test out to help narrow this down, thanks!
What you are hearing is the amplification of artifacts produced by down sampling the 32bit float source files to 16bit when compressed by FMOD. To resolve this issue I recommend you export your assets to 16bit using appropriate dithering before importing into FMOD.
By default when you export from Audacity it will apply dithering, if you disable dithering then amplify the playback you will notice the same artifacts.