Audio/Video Drift in ScreenFlow recordings
Topic: Audio/Video Drift in ScreenFlow recordings
Dear all
I'm using ScreenFlow to record video lectures that combine PowerPoint screen recordings with a video overlay of me talking.
The problem is that the video and audio my narration gradually drift out of sync (video slower than audio). Initially, the video lags behind about 3 frames at 30FPS, i.e., about 100ms. During the recording, the offset increases by about 3 frames per 15 minutes. After a typical lecture of 45 minutes, video and audio are therefore off by 12 frames (400ms), which is very disturbing because the lip movement and audio no longer match at all.
My recording setup is as follows:
- ScreenFlow 9.0.4
- MacBook Pro, 15" late 2013 model attached to an Apple Thunderbolt display running macOS 10.15.5
- Audio captured with M-Audio Air 192|6 USB audio interface, 48kHz sampling rate, directly connected to Mac without USB hub
- Video connected with Logitech C925e USB webcam, directly attached to Mac without USB hub
I can reproduce the same problem using a different USB audio interface and USB camera:
- Presonus StudioLive 12 USB mixer
- iSight USB video camera that is built into the Apple Thunderbolt Display
The problem is also independent of the sample rate and can be reproduced at 44.1kHz and 48kHz.
To verify this is a ScreenFlow problem and not a problem of my hardware setup, I did test recordings with QuickTime and OBS. Neither QuickTime nor OBS show any noticeable video drift but only a constant offset of about 3 frames.
- https://www.dropbox.com/s/q5upoivqhpr1q2e/ScreenFlow-AV-Drift.screenflow.zip?dl=0
ScreenFlow Recording 30 FPS, video: Logitech C925e @ 640x480, audio: M-Audio Air 192|6 @ 48kHz - https://www.dropbox.com/s/2ckc23zus0dzfkc/ScreenFlow-AV-Drift.mp4?dl=0
Same as above but exported as H264 in MP4 format - https://www.dropbox.com/s/mrk31zfrv37x6ei/OBS-AV-Drift.mp4?dl=0
Recording with OBS 25.0.8, video and audio same as above, recorded as H264 in MP4 format
In these test recordings I am recording myself making a hand clap every 15 minutes. This allows me to compare the audio peak and the frame in which my hands touch in the ScreenFlow timeline, or in Adobe Premiere for the recordings made with QuickTime and OBS. Watch for the hand claps around 0/15/30/45 minutes.
I would be grateful for any help in solving this problem.
Also, I would appreciate it if anybody could try to reproduce this problem using the hand clap test. Given that I can reproduce this problem with two different USB cameras / audio interface combinations I wonder how widespread this issue is.
Kind regards
Christian
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Very good and thorough test. Fill out the form and include that information. Post the case number here when you get it so I can track this as well.
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I have already opened a support case on May 9 (case number #00742883).
But Screenflow customer support is unfortunately unresponsive. The only reaction I got since June 3 is an email stating that the case was closed because of inactivity.
Can you re-open the case or shall I open another case?
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Christian Plessl It looks like they may have closed it because there were many days before getting your next response.
Open a new case and I'll see about the old case. -
CraigS I have opened a new support case #00753752
Also, I have added the premium support option hoping this will allow the support staff to investing more effort into resolving this problem.
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Christian Plessl I've also followed up with support to further investigate (reading your previously sent emails).
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I did additional experiments:
- I can also reproduce the problem with version 7.2 of ScreenFlow.
- The problem is also present when using both video and audio from the Logitech C925e webcam, though the drift appears to be slightly slower.
I was able to arrange a call with tech support. They don't know a solution either but confirmed that there are other customers experiencing the same problem.
Over the next days, I will some more experiments using a different Mac to exclude that the problem is specific to my machine.
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Christian Plessl Thanks for testing as we continue to investigate as well as you note. Please email support with your case number that you can verify the issue going back to 7.2. That may be important.
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I tested the built-in Facetime camera and built in microphone of my MacBook Pro and found that there is no audio/video synchronization drift but just a constant offset of about 3 frames (which is acceptable).
Any other configuration of my two USB cameras and two USB microphone interfaces did not work. Hence, I cannot do any high quality recording. This is terribly frustrating.
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Christian Plessl Using your case number email us that information.
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I asked a coworker with the latest MacBook Pro 2019 model to do some additional testing to verify that the problem is not specific to my machine. I cannot share the recordings but the results of my analysis, see below.
The bottomline is that the problem is not specific to my machine but can be reproduced with the latest MPB 2019 model and another machine with the same model as my MPB. The drift on the 2019 MPB model is a bit better, in particular, when recording audio and video from the Logitech 925e. But the sound quality is obviously lower than recording from a dedicated microphone.If you have a setup using a high quality USB cam and microphone, please let me know. Given that I'm able to reproduced the drift problem with so many different setups in Screenflow (but OBS studio and Quicktime work), the only reasonable conclusion seems to be that audio / video capturing is simply not working correctly.
Cheers
Christian
CraigS : an extended version of this report and an idea for a workaround has been added to support case #00742883. But considering that nobody has looked into this for months my hopes are low.
Test case 1:
- setup: MacBook Pro 2019 using Logitech 925e camera for video and sound
- initial audio / video offset: 3 frames @ 30 FPS
- no noticeable additional drift for a 1h recording
Test case 2:
- setup: MacBook Pro 2019 using Logitech 925e for video and MAudio Air 192 for audio
- initial audio / video offeset: 3 frames @ 30 FPS
- drift of about 3 frames per hours of recording (14 frames offset after 4h)
Test case 3:
- setup: MacBook Pro 2019 using Logitech 925e for video and internal microphone for audio
- initial audio / video offset: 3 frames @ 30 FPS
- drift of about -3 frames per hour of recording. (video is ahead of audio)
Test case 4:
- setup: MacBook Pro 2013 using Logitech 925e for video and audio
- same MPB model than mine
- initial audio / video offset: 3 frames @ 30 FPS
- drift of about 3 frames per hour of recording.
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Christian Plessl There's some interesting variations in that.
Test case 1 and Test case 4 both use just the Logitech for video and audio yet 1 has just an offset and 4 has a drift.
Test case 2 and 3 both use different sources for video and audio and has drift so there might be at least two different issues.
Thanks for testing. I'll report it. -
CraigS Yes, I have found only two cases where there is no drift but a constant offset: a) using the built-in Facetime camera and microphone of the MacBook Pro 2013, and b) using video and audio from a Logitech 925e webcam on a MacBook Pro 2019 (but not on the 2013 model). Unfortunately, none of these setups are really suitable for recording both, high quality audio and video.
Using the Logitec 925e on a MPB 2019 may be an option. But I find it very hard to justify buying a new MPB 2019 notebook for more than 3000$ as a workaround of a software problem.
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Christian Plessl We'll have to work on the fix since, professionally, it's common to use an external camera and an external audio source.
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CraigS I totally agree. So far, neither your customer support nor anyone else could recommend a camera / audio interface combination that works without flaws.
Until the root cause of the problem has been identified and fixed in software, you should provide recommendations for proven hardware configurations that can be used as a workaround in the meantime. And supporting these configurations should be a top priority of customer service.
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Christian Plessl This AppleInsider article mentions that T2 with USB2 devices and suggests USB3 and Thunderbolt audio interfaces. We haven't tested this and it may not cover other potential causes.
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CraigS My MacBook Pro does not have a T2 chip thus this cannot be the problem.
BTW: I have just confirmed that the recently released version 9.0.5 of Screenflow does unfortunately not solve the problem. But the release notes also did not mention any bugfixes in this direction.
Finally, I'm sharing an proposal for a workaround for the problem that was ignored by your tech support (Case #00742883).
I noticed that Screenflow has an option to record in a loop with a configurable duration. Unfortunately, this mode discards all but the last recording. If there was an option that allowed to keep all recording this might be a workaround to avoid excessive drift.
My assumption is that whenever a new recording is started, audio and video are synced again. Hence, one could do longer recording in shorter slices (e.g. 10 minutes) and merge all of these slices into a single track later on. If the merging of clips does not mess up the timing, this may be a way to bound the drift if it can be prevented that the initial audio/video offsets do not add up in the merging process.
I think this would be worth trying out and if your engineering could create an experimental build, I would be willing to test it. -
Christian Plessl Once we get this solved it will likely be a more graceful under the hood solution. Our internal reference for investigating the fix is FLOW-10489.
The issue of drifting sync isn't going to be fixed by external hardware (but can be improved on T2 chip Macs as noted above) since it has to do with the clock and sample processing relative to different sources.
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Hello CraigS ,
There is a solution about this issue? I'm running ScreenFlow 10 with the same problem.
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Guillermo Gonzalez Please make sure you've updated to ScreenFlow 10.0.3 which was just released a few days ago. ScreenFlow 10.0 had issues that were since fixed.
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CraigS Yes, my ScreenFlow version is 10.0.3 (31849). My videos was recorded yesterday, so the new version still has the same issue.
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Guillermo Gonzalez Please include all details about your system and sources and whether it's drift or sync offset. It must be enough detail so we can reproduce the issue.
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Could this be a frame rate issue (e.g. your project is 30fps and your camera is shooting 29.97fps)?
If the audio is captured at 30fps, and the video is 29.97 fps, the video will start off in sync and gradually drift ahead of the audio. I'm experiencing this and am trying to salvage the recording by bringing it into Final Cut.
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Alex Woolford said:
Could this be a frame rate issue (e.g. your project is 30fps and your camera is shooting 29.97fps)?The sync drift at that rate would be very slow but could show on a long recording.
Alex Woolford said:
m trying to salvage the recording by bringing it into Final Cut.You time "time stretch" in ScreenFlow by adjusting the speed in small amounts until you hit sync. I've created a feature request to create markers to make time stretching a bit easier (as it is in FCP) but it can be done in ScreenFlow.
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Hello, I just upgraded from Screenflow 8 to 10, and downloaded the latest version.
I recorded a test video with the following settings: 1) Camera: Fujifilm X-S10 connected via Elgato Camlink 4k (HDMI), 2) Microphone: Shure MV7, connected via USB, and 3) Recording of my desktop. I am using a 2021 Macbook Pro M1 Pro.The audio/video are in sync in the timeline. I exported the video as an MP4 in 4k. Here is a link to the video. As you can see, the audio and video are out of sync right from the start.
I did some research on the forums and noticed some discussion about frame rate. My X-S10 is configured to shoot in 29.97. I tried exporting the clip as both 30 fps and 29.97 fps, but it's equally out of sync in both cases, and as you can see, it's out of sync right at the beginning—which probably wouldn't happen if this were a frame rate mismatch.
Also, both the Shure MV7 and the Elgato Camlink 4k are connected to an OWC Thunderbolt 3 hub, which is in turn connected to my Macbook Pro. This setup works fine for doing recordings with other software, including Squadcast.fm. And, again, the audio and video are in sync in the timeline, so it doesn't seem to be a capture/hardware issue, but something that is happening in the export.
Thanks in advance for your help. -
Chris Kresser said:
The audio/video are in sync in the timeline. I exported the video as an MP4 in 4k. Here is a link to the video. As you can see, the audio and video are out of sync right from the start.Perhaps you can send us a link to the document so we can examine and do a test export on our systems.
Chris Kresser said:
it doesn't seem to be a capture/hardware issue, but something that is happening in the export.Given your description of the issue I'd agree. This is why we may need to see the document. We'd need to look at timeline vs export.
Are you using one of our export presets unaltered? If not please test.
Also test with an Apple ProRes preset to see if this is specific to x264 encoding.It's not clear what your export settings are. That might be part of the issue. We'd need that. A screenshot is best as people often leave out the details in their descriptions.