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TOPIC: Audio/Video Sync Test Clips

Audio/Video Sync Test Clips 3 years, 8 months ago #130612

  • khaver
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Inside the attached zip are 2 clips (1 for 30fps projects and 1 for 25fps projects) to test audio to video sync issues with your system.

Import the clip into a project and play. Watch and listen for when the audio blip and flash coincide and note what the subtitle says. If the sync is not 0 frames and 0.00 ms, then your system has sync issues.

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Last Edit: 3 years, 8 months ago by khaver.

Re: Audio/Video Sync Test Clips 3 years, 8 months ago #130613

  • geomcd1949
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Thanks, khaver. Can you be more specific on what exactly we should watch and listen for?
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Re: Audio/Video Sync Test Clips 3 years, 8 months ago #130616

  • khaver
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The clip will start out with an audio blip a certain number of frames/milliseconds ahead of the flash. It will do this 4 times and the next 4 times the audio blip will be 1 frame closer to the flash and so on throughout the clip. You will notice that at the middle part of the clip it shows 0 frames and 0.00 ms. This is where the sound of the audio blip and flash should coincide on your system.
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Re: Audio/Video Sync Test Clips 3 years, 8 months ago #130620

  • geomcd1949
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Aha! What a fantastic tool! And if used in v14 in Fixed layout, Audio mode, the sync can be checked by eye alone.
North Carolina, USA
Ubuntu 20.04 LTS
2x2.7 GHz E5-2680
500GB SSD and1TB HDD
64 GB DDR3 10600
Quadro K4200
~X-Keys Pro 68 key USB Jog/Shuttle controller
*Galaxy S7 with Filmic Pro*
*JVC GY-HM150*

Re: Audio/Video Sync Test Clips 3 years, 3 months ago #146740

  • briandrys
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I've created a new thread for the Android phone sync issue

www.lwks.com/index.php?option=com_kunena&func=view&catid=8&id=146728&Itemid=81#146728

Please keep the replies here for issues or suggestions directly related to khaver's test tool. Don't put messages about the sync issue itself here, instead create a new thread, where your audio/sync problem can be directly dealt with.

Re: Audio/Video Sync Test Clips 3 years, 3 months ago #146742

  • hugly
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Great work, thank you, khaver!

May I point out that this great tool provided by khaver can be used to detect sync issue caused by latencies of the audio chain (hardware and software) of the computer used. Let's call it "audio monitor delay". On low powered computers this delay can be significant and clearly audible (100 milliseconds and above).

The phenomenon affects audio monitoring (playback in preview) only. It is not present in exported file. It doesn't affect the audio waveforms on the timeline. Audio is always too late (delayed). It's a constant shift of audio, audio sync isn't drifting. It can be ignored while editing when audio is included in the imported video file (and correctly synced there).

When separately recorded audio is used and manually synced in Lightworks the amount of audio monitor delay should be known and it must be compensated. Because audio monitor delay doesn't affect waveforms on the timeline, the waveforms can be used to sync audio with video correctly, even when significant audio monitor delay is present (watching the waveform, not listening to the audio).

Sync issues caused by sources recorded with variable frame rates
(the "Android phone sync issue" for example) have nothing to do with audio monitor delay. They are caused by the footage itself and not by the computer used. With V14.0 and earlier **, they can only be corrected by converting the affected files using third party software prior to import into Lightworks to a format with constant frame rate.

** Edit: With Lightworks V14.5 support of variable frame rate in h.264/MP4 format has been introduced. Sync issues don't occur with embedded audio, as long as the audio sample rate is constant (which is true for most formats) and the nominal frame rate is a standard frame rate. Most common standard frame rates are 23.976, 24, 25, 29.97, 30, 48, 50, 59.94, 60, 100, 120, 240 fps.
It's better to travel well than to arrive...
Last Edit: 1 year, 2 months ago by hugly.

Re: Audio/Video Sync Test Clips 2 years, 3 months ago #175984

  • lanyi.balazs
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Do you have any tips on how I could fix this audio monitor delay? It's driving me mad...

Re: Audio/Video Sync Test Clips 2 years, 3 months ago #175995

  • hugly
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Hello,

Give Lightworks V14.5 a try. Overall performance and the audio system have been improved including some bug fixes. You'll find it under Downloads on top of this page.

There are also new proxy formats. When using demanding footage the internal proxy workflow is a way to increase performance significantly and might help to reduce audio monitor delay as well.

Let us know how this works for you.
It's better to travel well than to arrive...

Re: Audio/Video Sync Test Clips 2 years, 3 months ago #175998

  • lanyi.balazs
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I will. Thanks!

Re: Audio/Video Sync Test Clips 2 years, 3 months ago #176001

  • lanyi.balazs
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OMG! thank you! It's way better now. Fingers crossed it'll last through my project...

Re: Audio/Video Sync Test Clips 2 years, 3 months ago #176002

  • hugly
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That's good to hear. Let us know if it doesn't last through your projects.
It's better to travel well than to arrive...

Re: Audio/Video Sync Test Clips 1 year, 3 months ago #196885

  • wevans3
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Under powered systems....
could you clarify that designation. Would it be a bottleneck in RAM?

I have a pretty good processor, but only 16GB or ram. Thus why i asked about the RAM.
Last Edit: 1 year, 3 months ago by wevans3. Reason: extraneous info removed

Re: Audio/Video Sync Test Clips 1 year, 3 months ago #196892

  • hugly
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Not so easy to define 'underpowered machine', since editing performance is influenced by the computer configuration and the material used.

The probably most intuitive definition is, if your edits show a significant audio delay in preview, your machine is underpowered for the material you use.

Audio delay appears to be a timing/buffering issue. The preview pipeline uses CPU, RAM, the main bus, GPU and VRAM, and file I/O (HDD). The main worker is the CPU. Above 8GB of RAM, it's very unlikely that you'll see some remarkable performance gain when upgrading only memory.

Before investing in bare metal, I'd suggest trying the Internal Proxy Workflow to see if it reduces audio delay in preview. It will surely increase overall performance significantly.

Most important, if you still run V14.0, upgrade to V14.5 - it's worth it, due to many fixes and enhancements.

Edit: Maybe, my epic explanation hides the essential answer to your question. With 16 GB of RAM installed, the answer is: No.
It's better to travel well than to arrive...
Last Edit: 1 year, 3 months ago by hugly.

Re: Audio/Video Sync Test Clips 1 year, 3 months ago #196897

  • briandrys
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wevans3 wrote:
Under powered systems....
could you clarify that designation. Would it be a bottleneck in RAM?


Recommended System Specs

Intel i7 chipset or faster, fast AMD chipset
3GB RAM or higher
Two high-resolution displays (1920 x1080) or above
PCI Express graphics card (NVIDIA or AMD) with 1GB or higher and support for DirectX 9 (Windows only)
Separate media and system drives (these can be internal or external as long as the the interface is suitably fast
Compatible sound card
200MB Disk space for Lightworks installation

Note that editing HD and 4K on 3GM of RAM will probably cause issues. That you need suitably fast separate media and system drives and a basic graphics card may have difficulty if you have a lot of effects.
Last Edit: 1 year, 3 months ago by briandrys.

Re: Audio/Video Sync Test Clips 1 year, 3 months ago #196916

  • wevans3
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Thank you!
I will try the workflow. I exceed all the hardware specs you guys listed I LOOOOVE my R6 AMD
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