Audio Sync Issue on Project but not on Clip [VS X9]

[AshenTemper]

Hi all, hope you can help me with this. I tried searching but it appears my google-fu is off today.

I have a video clip I made from Hudl.com of some of my daughter's volleyball that I want to use VS to clean up and do a little more with. I've been using VS for years but getting the video from Hudl is new and I feel the main culprit.

I take the entire file (and it is about 10m long) and put it in to a new project and the audio for each section has about 4 seconds of silence at the end of each. When I play the video, it is almost as if the audio is slightly sped up and that is why (although I could be imagining that). The odder thing is if I cut the video up into segments, it does not have that issue when I play it as a Clip but it does when I play it as a Project. Due to that, no matter what, the output copy will have the out of sync audio because it renders as a Project.

The original video stats:

• Length: 10:43
• Codec: H264 - MPEG-4 AVC
• Resolution: 1280x720
• Data rate: 3057kbps
• Frame rate: 29.225634
• Decode format: Planar 4:2:0 YUV
• Codec (Audio): MEPG AAC Audio (mp4a)
• Bit rate (Adutio) 96kbps
• Channels: Stereo
• Sample rate: 44100 Hz

My output settings:

• MPEG-4 Files
• 24 bits, 1280 x 720, 29.97 fps
• Frame-based
• H.264 Main Profile Video: 3057 Kbps, 16:9
• 44100 Hz, 16 Bit, Stereo
• MPEG AAC Audio: 96 Kbps

My System:

• VideoStudio: 19.5.0.35 (64bit Ultimate)
• Operating System: Windows 10 Home 64-bit
• CPU: Intel Core i5 4690 @ 3.50GHz
• RAM: 8.00GB Dual-Channel DDR3 @ 666MHz (9-9-9-24)
• Motherboard: Gigabyte Technology Co. Ltd. Z97M-DS3H (SOCKET 0)
• Graphics: 2047MB NVIDIA GeForce GTX 750 Ti (EVGA)
• Storage: 223GB Crucial_CT240M500SSD1 (SSD) // 1397GB Seagate ST31500541AS (SATA) // 232GB Samsung SSD 850 EVO 250GB (SSD)
• Audio: High Definition Audio Device

I have tried this both with using and disabling SmartRender and the outcome has been the same.

I've been using VS since X7 and this is the first I've run into the issue and I have a feeling it is due to the video I get from Hudl. Speaking of which, in case it helps:

• Original Video: https://www.dropbox.com/s/wobgx7wromcn4 ... L.mp4?dl=0
• Output from VS: https://www.dropbox.com/s/s139p1e3rrjmg ... p.mp4?dl=0

Instead of watching the whole video, go to 10:24 on the first and 6:30 on the second and watch that volley (play) and you'll quickly see what I'm talking about.

Any ideas on what I'm doing wrong? Like I said, I've been using VS for a few years and this is the first I've run across this problem.

[Ken Berry]

Welcome to the forum -- and thank you for all that detail.

The one thing that stands out is the frame rate for the Hudl footage: 29.225634. This means both the video and audio are set to run at this rate. I wonder if the original footage was shot on a cell phone as many of the more recent ones are starting to use variable frame rates like that. They play back fine in their native state, but as soon as you include them in a project which has a different frame rate -- as you have done using the standard NTSC frame rate of 29.97 fps -- then out of sync problems arise.

What to do about it, however, is another matter. My first instinct would be to convert the original footage -- though back to mpeg-4 -- using a third party converter. Some of us here use Format Factory which does a good and quick job, though there are a myriad of other converters out there. If you go for Format Factory, just be careful to read all the dialogue boxes in the installation process as it offers to install other software you will not want. But the converted video will hopefully have extended the audio slightly to fit the slightly higher frame rate of the video and should now no longer go out of sync when you insert the converted video into your project.

If that doesn't work, then a slightly more work-intensive method might be necessary. With the problematic clip in the timeline by itself, go to Share and select Audio as the output and standard .wav as the format. This will create a new audio file for the video. Back in your original project, including the Hudl footage, I would mute the latter, and insert the .wav file in one of the audio tracks below that clip. Hopefully they will now line up in sync. If they don't then you can cut the audio file into sections and move them along the timeline until they line up with the video they are describing.

[AshenTemper]

Thanks, Ken! The school uses an okay camera. My assumption is that Hudl actually outputs in the format on purpose since part of how they make money is by people purchasing the footage through them (which I do). I just wish that when you purchase it, it would output it to something standard.

I'll try converting it with Format Factory first and see if that does the trick. Thanks for the info! I'll report back with my findings.

[AshenTemper]

Weirdly enough, when I ran it through Format Factory, it had much the same issue. I used something to pull the audio out of the video and I think that shows where the issue is. When I put the video in (muted) and then the audio file in another track, they are not the same length. The video is 643.456 seconds but the audio is 639.660 seconds. Not sure if it is the weird frame rate of the video or something else. I sent a request to Hudl seeing if they will tell me exactly what properties and codecs they use for their system.

[asik1]

The original footage
Frame rate mode : Variable
Frame rate : 29.226 fps
Minimum frame rate : 0.478 fps
Maximum frame rate : 30.236 fps

[AshenTemper]

Hey all, heard back from Hudl so wanted to post this here in case it helps anyone else:

You managed to stumble on to a little bug that we've had in our system for a while now. Essentially, what were 30 (29.97) FPS videos end up downloading as something slightly less than 29.97 FPS. In your case, it looks like ~29.23 FPS.

When your video is uploaded to Hudl.com, it's broken into small fragments of video, in .ts format. When you download the video, all those .ts files are combined into a single .mp4 file. Unfortunately, there's a limitation in the program we use to create that MP4 that can create tiny differences in the video length before & after conversion (details at https://trac.ffmpeg.org/ticket/4768 if you're interested). The resulting issue is what you're finding here, where the downloaded video is marginally longer than what you uploaded and see on Hudl.com, although the audio seems to be unaffected.

I hope that makes sense, although I don't know if it's helpful for you. Let me know if there's anything else I can answer that might be more useful!

Which lines up with what I was experiencing. My simple fix to it was to export the audio and then stretch (timelapse) it to equal the same length as the video. There was one spot near the end where I had to tweak it due to this but, overall, it worked quite well.

[Ken Berry]

Sounds a bit strange, but at least they responded with detail! And glad your work-around worked!! Given that the time difference between audio and video was so short (4 seconds over 10 minutes), stretching the audio would not result in any audible distortion... If the differential were much longer, you might have to resort to extracting the audio and cutting it into individual bits which you would then place separately under the parts of the video to which they relate, as I suggested above.

[AshenTemper]

Sounds a bit strange, but at least they responded with detail! And glad your work-around worked!! Given that the time difference between audio and video was so short (4 seconds over 10 minutes), stretching the audio would not result in any audible distortion... If the differential were much longer, you might have to resort to extracting the audio and cutting it into individual bits which you would then place separately under the parts of the video to which they relate, as I suggested above.

Yeah, that is pretty much what I was doing in the first place and it was driving me crazy trying to figure out what I was doing wrong. I don't mind cutting up the audio but it being off was a head scratcher (at the time). For the most part, Hudl is generally for 1 - 2 min clips so I imagine most people don't even notice the issue. I try to get the bang for my buck and do a 10m highlight video but I don't think you can stretch it much more than that (although, I haven't tried).