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TOPIC: Strange Quality Decline

Strange Quality Decline 1 year, 8 months ago #121902

  • donnerkebab42
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Hi folks.

I'm new to Lightworks and am loving it so far, apart from this strange little tick. The quality of the video decreases 36 seconds into the edit.

I've changed everything that I can think of, but it hasn't improved. I've even redone the scene in multiple formats, and even sliced it into sections, thinking that there was a file-size-issue but still nothing.

I've attached a screen shot of the lightworks project the LHS shows the poor quality, on the RHS is 1 frame before.

The second image is how they both look in my media player window.

If anyone has any ideas, I'd really appreciate the help. It's for work not pleasure and my deadline is running out!

Thanks in advance.

donnerkebab42
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Re: Strange Quality Decline 1 year, 8 months ago #121903

  • hugly
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Hello and welcome!

I've even redone the scene in multiple formats

Would you please explain what formats did you use?
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Re: Strange Quality Decline 1 year, 8 months ago #121905

  • donnerkebab42
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It's currently an MP4 at 720x480. But have tried AVI (disaster) and PNG images (so slow) and have tried the following alternative frame rates: 640x480, 960x720, 1280x720.

Re: Strange Quality Decline 1 year, 8 months ago #121906

  • donkpow
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I've attached a screen shot of the lightworks project the LHS shows the poor quality, on the RHS is 1 frame before.
The LHS is playback of the source material (blue border). You should be able to export a single png image of that frame for more careful analysis. Check the key assignment panel for a shortcut to do that.
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Re: Strange Quality Decline 1 year, 8 months ago #121912

  • RWAV
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It's currently an MP4 at 720x480 have tried the following alternative frame rates: 640x480, 960x720, 1280x720
Are you saying you are generating your animations at those frame sizes? .mp4 is your container format - what is the codec you are using? Are you certain all your animations have been written at the same codec data rate? 720x480 is almost/not-quite standard NTSC 4:3 size you are using it as 16:9 which is a non-square pixel format or is being interpolated into 16:9 by your graphics card - have all your animations been written as either interlaced or progressive and not a mix of both? Does the filecard/ContentManager list of your clips have a progressive/interlaced switch - LW is possibly assuming your material is NTSC Interlaced? I'd suggest using a 16:9 format like 1280x720 may be a good idea. What is the setting of your LW Main Project Tab/Video/Output Format?

Other than the report that the quality loss occurs suddenly after a number of seconds play - which I cannot recall ever being reported as a LW issue and it may be worth investigating your graphics card as a problem source - the quality you are seeing is not far off what one might expect from interpolating NTSC sized 4:3 probably AVC codec material into 16:9 and viewing it on a monitor at some other interpolated image size.

Are the bad/good bits always bad/good - if so could you post a MediaInfo analysis of each - if not please post a MediaInfo analysis of a typical video file.
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Re: Strange Quality Decline 1 year, 8 months ago #122175

  • donnerkebab42
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"Check the key assignment panel for a shortcut to do that"

Sorry, where is the key assignment panel?


I'm using a software program called Muvizu to create the animations. I do each scene, render and export as an MP4 at 720x480.

There's no option to change the codec with the MP4 output, only the Bitrate, which I've left at 2000. As it's a preset codec, all the animations have been saved the same.

As for the progressive/interlaced animation differences, they're all the same. I haven't changed any settings, the animation program is more of a drag-and-drop director-style application rather than a creation animation (I don't have the skills for that).

I'm unsure of the graphics card that I have, but it's a work computer, that was custom-built specifically for design and editing, so I'm guessing it's a beast.

So, you think I should re-render and export all of the clips at 1280x720?

Yes, all of the scenes play clearly in windows and VLC media, but when put into LWKS, all the scenes after the 35 second mark have this quality. The first 14 are fine and the remaining 21 aren't.

Sorry to be a complete newb, but how do I formulate a MediaInfo anaylsis?

Many thanks.

Re: Strange Quality Decline 1 year, 8 months ago #122182

  • donkpow
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Page 207 of the User Guide shows how to access the key assignments.

Do you use screen capture software to record the animation sequences?
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Re: Strange Quality Decline 1 year, 8 months ago #122184

  • donnerkebab42
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Thank you, I'll have a look at that now.

Here's what I'm using... www.muvizu.com/ It has it's own built-in "movie-maker".

Re: Strange Quality Decline 1 year, 8 months ago #122185

  • donkpow
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I'm still waiting for a decent image, preferably a single frame at full resolution, in order to see the problem.
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Re: Strange Quality Decline 1 year, 8 months ago #122186

  • donkpow
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I can't spend a lot of time on this today. Here is the Muvizu user manual.

https://www.muvizu.com/download/muvizu-instructions-v2.pdf
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Re: Strange Quality Decline 1 year, 8 months ago #122187

  • donnerkebab42
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I've read that cover-to-cover, hence why I'm posting on the Lightworks forum for help, and not the Muvizu forum.

I apologise for taking your time, like I said at the beginning, I'm new to this whole process.

I've checked page 207, found the key assignments, and alas, there isn't one for "save current frame" so I'm just reading through on how to amend this.

Whilst also, re-rendering and re-saving the whole project as RWAV has suggested.

This may explain my not-so-speedy compliance. Sorry, moving as quick as I can.

Re: Strange Quality Decline 1 year, 8 months ago #122188

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Here's the frame image
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Re: Strange Quality Decline 1 year, 8 months ago #122189

  • donnerkebab42
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And, here it is from the next scene

Many thanks.
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Re: Strange Quality Decline 1 year, 8 months ago #122192

  • hugly
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Thank you for the new images.

It's cleary visible that you're dealing with interlacing and/or scaling artefacts.

As you asked above. Yes, rerender everything to 1280x720 progressive which means non-interlaced. This will produce the best possible quality for 720 (Youtube) export with Lightworks. If you're going to publish on Vimeo with a Pro account 1920x1080 progressive would be best choice.

Please check also frame rate and frame rate mode.

The frame rate should be one of the following: 23.976, 24, 29.97, 30, 48, 50, 59.94, 60 frames per second. The higher the better quality you'll get for fast movements but rendering time will increase accordingly.

The frame rate mode must be constant (and not variable).

To check the technical parameter on extisting video files you can use Mediainfo Lite or MediaInfo.

Let us know how this works for you.
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Last Edit: 1 year, 8 months ago by hugly.

Re: Strange Quality Decline 1 year, 8 months ago #122196

  • donnerkebab42
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That's brilliant, thank you.

I'll let you know how I get on!
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