Premiere Pro Audio Desync

Indus Monk · July 23, 2018

Hello Everyone, I've been trying to edit some PUBG footage for my friend, but in Premiere, there is a huge issue of audio desync. I used Sony Vegas instead, but it's not something i'd want to use again; simply put. From what I can gather, I have to transcode the footage in blender to reduce the frame rate. But I only have an i5 4690k, so the transcode takes hours. I was hoping if there was a faster way round this problem? I can't use Final Cut, since I don't have an iMac or Macbook. If it heIps,I can switch to Avid Media Composer; since that's what I learnt at my internship. I'd rather not use Davinci Resolve because it lacks CUDA acceleration. (from what I can gather)

Note: PUBG footage is generally very out of sync

skimmilk5 · July 23, 2018

Is it desync or is it drift? There's a fairly substantial difference between the two...

If it's desync, just sync by hand. Buying software to sync isn't worth it unless you have eight hours of footage and twelve hours of audio in three minute chunks and it's all over the place. You can try the sync tools in Premiere, but go in with the anticipation that they won't work correctly. Select both your audio and video clip, as well as your scratch audio, right click, and synchronize. Select which is your scratch audio track, then sync it up.

Indus Monk · July 24, 2018

13 hours ago, kimsejin5 said:

Is it desync or is it drift? There's a fairly substantial difference between the two...

If it's desync, just sync by hand. Buying software to sync isn't worth it unless you have eight hours of footage and twelve hours of audio in three minute chunks and it's all over the place. You can try the sync tools in Premiere, but go in with the anticipation that they won't work correctly. Select both your audio and video clip, as well as your scratch audio, right click, and synchronize. Select which is your scratch audio track, then sync it up.

what is the difference between desynce and drift?

skimmilk5 · July 24, 2018

TLDR: Desync means that if you move the audio left or right, eventually it will line up perfectly. The audio is the exact same length as the video.

Drift is the actual slight length change that occurs because of timecode shifts. You should always try to correct your sync first, before trying to correct for drift. This is explained below in much more detail that may or may not be useful.

History lesson time!

Way back in the era of film, we would record in true 24FPS or 30FPS (or 25FPS for our PAL brethren), and audio would be recorded on tapes at 32kHz (normally, we're not going to delve into the world of custom equipment with custom sample rates). As it turns out, this was perfect for sync, and it meant that we could simply line up the slate (that clapperboard thing?) video with the audio, and it would sync up perfectly. Come the digital age, we kept the true 24FPS (or 30FPS), but AES (the Audio Engineering Society) changed the standard from 32kHz to 44.1kHz or 48kHz for improved fidelity and quality, as well as an increased frequency range. Unfortunately, this would make the audio slightly longer (in the case of 44.1kHz) or slightly shorter (in the case of 48kHz). While a few samples that last a millisecond off doesn't sound like much, when we're talking about a 1.5-2 hour movie, the audio "drift" can get so bad that audio ends up several seconds off. Additionally, when combining two audio sources with different sample rates (say, 44.1kHz and 48kHz), these will also drift from each other.

To combat drift, the AES suggested to the camera manufacturers to develop several new frame rates that would line up on a sample-by-sample basis with 44.1kHz and 48kHz. In return, we got 23.976, 29.97 and 59.97FPS. What appears to be 30FPS on most digital devices is actually 29.97FPS! The time difference is just so small that we can't tell. While these approximations are close enough for most consumers, who don't care about 0.03FPS, and frankly can't tell. However, large movie productions will often use a true 24FPS camera and recording rate (these cameras are often marketed as being able to record in true 24FPS, it's a big selling point), and will record audio at 48kHz, then correct for this drift in postproduction by literally dragging the audio to be just a smidge longer, then correcting for pitch. Oh, computers, how thee hath maketh our lives easier.

Indus Monk · July 25, 2018

10 hours ago, kimsejin5 said:

TLDR: Desync means that if you move the audio left or right, eventually it will line up perfectly. The audio is the exact same length as the video.

Drift is the actual slight length change that occurs because of timecode shifts. You should always try to correct your sync first, before trying to correct for drift. This is explained below in much more detail that may or may not be useful.

History lesson time!

Way back in the era of film, we would record in true 24FPS or 30FPS (or 25FPS for our PAL brethren), and audio would be recorded on tapes at 32kHz (normally, we're not going to delve into the world of custom equipment with custom sample rates). As it turns out, this was perfect for sync, and it meant that we could simply line up the slate (that clapperboard thing?) video with the audio, and it would sync up perfectly. Come the digital age, we kept the true 24FPS (or 30FPS), but AES (the Audio Engineering Society) changed the standard from 32kHz to 44.1kHz or 48kHz for improved fidelity and quality, as well as an increased frequency range. Unfortunately, this would make the audio slightly longer (in the case of 44.1kHz) or slightly shorter (in the case of 48kHz). While a few samples that last a millisecond off doesn't sound like much, when we're talking about a 1.5-2 hour movie, the audio "drift" can get so bad that audio ends up several seconds off. Additionally, when combining two audio sources with different sample rates (say, 44.1kHz and 48kHz), these will also drift from each other.

To combat drift, the AES suggested to the camera manufacturers to develop several new frame rates that would line up on a sample-by-sample basis with 44.1kHz and 48kHz. In return, we got 23.976, 29.97 and 59.97FPS. What appears to be 30FPS on most digital devices is actually 29.97FPS! The time difference is just so small that we can't tell. While these approximations are close enough for most consumers, who don't care about 0.03FPS, and frankly can't tell. However, large movie productions will often use a true 24FPS camera and recording rate (these cameras are often marketed as being able to record in true 24FPS, it's a big selling point), and will record audio at 48kHz, then correct for this drift in postproduction by literally dragging the audio to be just a smidge longer, then correcting for pitch. Oh, computers, how thee hath maketh our lives easier.

Still can't understand Audio drift, Though I'd like to know more about this.

My issue is that the audio is, initially at least, a few milliseconds ahead or behind. Then it becomes incredibly more noticeable as the video goes on. Also, the clip is over an hour long as well.

skimmilk5 · July 26, 2018

Yep, definitely drift.

If you feel like fixing it manually (or you can't afford specialized software to correct for it automatically), use this article: http://www.designtrek.com/how-to-sync-video-at-48-khz-with-audio-at-44-1-khz-with-adobe-premiere-pro#sthash.iqWToINA.dpbs (maths are required).

If you can afford it, PluralEyes from Red Giant is a personal favorite for automatically correcting drift and syncing up automagically. You just drag in your audio, drag in all your video, and hit synchronize.

To clarify what drift is, think about your video operating like a perfectly timed atomic clock, and it's the basis for other clocks around the world. Think of your audio as a cheap quartz clock from Ikea. Your Ikea clock is going to run slightly fast or slightly later than the perfectly timed atomic clock, no matter how carefully you set it up, so if you come back in an hour, they'll be off by just a little bit, and if you left them alone for ten years, well, you can imagine how far off the two clocks would be. Drift correction basically continually adjusts the Ikea clock to be in line with the atomic clock so that they never experience even a slight delay. Makes more sense?