Audio Out of Sync with Waveform After Editing + More

Phil_P wrote on 1/20/2021, 6:05 AM

This is rather tiring...

Just spent a few hours editing a video. The video is a tutorial so mainly the audio needed editing, cutting and joining. etc.

I breathed sigh of relief as one does when an edit is finished. Then skipped back to check things.

Oh dear. Half the audio has glitches and is out of sync.

Restarted a few times and found that what I have been editing is not necessarily correct. As playing back the audio does not match with the Waveform.

On top of which, some words are repeated and some missing altogether.

The source recorded from OBS is fine.

So I will now have to basically start again. Maybe I should create a proxy video as the whole thing did become very sluggish? Even though it is just one track of video / audio.

Has anyone come across this?

Please bear in mind I am an audio professional, producer and composer etc. I also keep my machine and drivers etc. meticulously maintained and up to date. So before anyone asks I can tell you I have the latest drivers for my video card and all other devices.

Here is the Source Video/Audio info in case it helps:

 

General
Unique ID                                : 242785207305745306614154138495989011246 (0xB6A6BAE68D3C3668695794DA81BB532E)
Complete name                            : D:\Vegas Projects\WL Bluecat\2021-01-20 14-42-10.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 358 MiB
Duration                                 : 13 min 21 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 3 748 kb/s
Writing application                      : Lavf58.29.100
Writing library                          : Lavf58.29.100
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L5.2
Format settings                          : CABAC / 2 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 2 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 13 min 21 s
Bit rate mode                            : Variable
Maximum bit rate                         : 65.0 Mb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 60.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : A_AAC-2
Duration                                 : 13 min 21 s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 SPF)
Compression mode                         : Lossy
Title                                    : Track1
Default                                  : Yes
Forced                                   : No

 

Comments

Musicvid wrote on 1/20/2021, 8:53 AM

Capture in OBS using the x264 software encoder, or a lossless intraframe if you are picky, rather than a machine codec.

Kids and gamers who don't care anything about quality and want really fast capture frame rates should continue using their hardware encoders ;?)

Some starting recommendations for Vegas users are here -- Experiment:

https://www.vegascreativesoftware.info/us/forum/faq-what-obs-studio-settings-work-well-with-vegas-pro--109925

Phil_P wrote on 1/20/2021, 12:43 PM

Hi Musicvid, Thanks for the tips. I have been using OBS since its inception and in fact have it set up exactly as needed for top quality 4K streaming and recording. The steps on that guide really do not apply to my case they do not show advanced settings and the best settings for 4K capture.

I will try the software encoder and Mp4 wrapper fwiw and see how that effects the audio.

I have even done tutorials and classes on it. The issue is not with the video at all. Maybe I did not explain correctly.

The issue is with the audio track. After making some edits the audio becomes out of sync with the waveform display of the audio. On top of it being out of sync, parts of it just disappear and start repeating. Obviously as side effect of this is that video also looks out of synch.

I tested this with the video removed completely.

It takes about 10 minutes of editing before the trouble starts. You will then for example delete a section of footage and the following section will not play the audio that it was actually supposed to play.

I will try the software encoder fwiw and see how that effects the audio.

I simply ask again if anyone else has come across this or similar issue? Audio becoming out of sync with the audio waveform.

nb. I am also an avid gamer, mainly flight sim which I use for own PPL training, (yes I fly light aircraft) but I do stream audio projects and production, perhaps your obvious disdain for gamers could be adjusted. Some of us are actually quite technically savvy.

Thanks again, I'll post back with results once I have spent the day recreating the entire project. :-)

Phil_P wrote on 1/20/2021, 1:00 PM

@Musicvid, I just read my post back and realised it sounded a bit condescending. Rather than editing it all I just thought I should explain that it is not intended that way. I am actually smiling while typing but you wouldn't know that. Your suggestions and time are of course appreciated. Thanks. P.

Musicvid wrote on 1/20/2021, 2:42 PM

@Phil_P

You are not condescending, and you are indeed correct "within the context" of your experience.

The thing you may not be fully aware of is the different decoding requirements of a nonlinear editor like Vegas, which must unpack to raw bits for editing, as opposed to normal interframe playback environments, which do a fairly good job of fudging their way through all kinds of errored blocks and frames, and in fact "looks" pretty good on your local screen or Youtube.

As to the inherent drawbacks of machine encoders, especially for digital intermediate use, including their tendencies to sacrifice both quality and efficiency for the sake of speed, even to the point of introducing audio sync errors on the timeline, the characteristics are well documented and tested by me and many NLE producers here and elsewhere; I won't bother you by repeating them here.

The steps on that guide really do not apply to my case they do not show advanced settings and the best settings for 4K capture.

They do, however, implicate a software encoder for successful transport to Vegas, of which you were not aware.

Now, I suggest you read even farther down that thread and at least glance at my starting suggestions for lossless intraframe capture in OBS, and at least consider the possibility that this is also not our first rodeo. The files will be many times larger than your lean 3.8 Mbps hardware captures at 4k resolution.

Again, welcome to the discussions, and I'm sure that as you adapt your gaming and entertainment experience to the realities of different encoding architectures in Vegas, you will solve your issues rather quickly. Since you are also in the entertainment end of the business, you might enjoy glancing at my signature as well.

Best Regards,

 

Phil_P wrote on 1/20/2021, 11:30 PM

Thanks again @Musicvid I will read more of that thread and of course try some experiments and post back if I come across anything useful. 🙏

Musicvid wrote on 1/21/2021, 12:13 AM

try some experiments

That's the important part, of course, because many of us are accustomed to achieving visually-to-mathematically lossless results in OBS and Vegas, with proper sync of course.

Grazie wrote on 1/21/2021, 12:21 AM

@Musicvid, I just read my post back and realised it sounded a bit condescending. .....I am actually smiling while typing but you wouldn't know that. Your suggestions and time are of course appreciated. Thanks. P.

@Phil_P - Douh, we knew that! You’re wearing that Mask. Can always do with a smile 😃.

 

walter-i. wrote on 1/21/2021, 3:50 AM

@Phil_P - Douh, we knew that! You’re wearing that Mask. Can always do with a smile 😃.

I'm sure of that too! 😉

Just a little anecdote because it goes well here:
My grandson - 8 years old - recently said:
"I like to wear the mask - I can show someone my tongue without them noticing ......"☺️

Phil_P wrote on 1/21/2021, 3:55 AM

Just thought I would post back. I got around this by exporting the audio as WAV with no edits. Then pulling the audio back in and deleting the video audio. Grouping the two and off you go. No issues apart from very sluggish editing (due to 4K content I guess).

Of course this does not solve the issue nor indeed help understand it. And I did obviously have to start eth whole edit from scratch.

I will of course try some of the suggestions with full new recording soon.