What the heck's the deal with MPEG2 jagged edges?

scissorfighter wrote on 3/30/2003, 6:33 PM
So I've got some DV tape that I captured with VV4. The end goal is to render it to MPEG2 for DVD. Problem is, there's a terrible amount of "jagged line noise" in the picture when the camera pans left or right, both in the avi file as displayed in the timeline and preview window within VV4, and in the rendered mpeg2 file. As other people have mentioned in the forum, it's particularly noticable when a scene has vertical lines in it (for example a picket fence) and the camera pans horizontally. The vertical edges of the picket fence become like the teeth of a saw while the camera is in motion. No velocity envelopes are applied to the video.

At first I thought this was just a fact of life when converting DV video to MPEG2. But then I tried using another software package to render the original AVI file to MPEG2. Using the trial version of CinemaCraft Encoder SP, the resulting MPEG2 file looks just fine, with no distortion or "jagged edges" whatsoever when the camera is in motion. Same bitrate, same "advanced" settings (as far as I can tell,) same source file, etc. CCE SP did a great job, and it looks good. What's the problem with Vegas?

I tried experimenting some more, and found that if I rendered the video out of Vegas as uncompressed AVI (or NTSC DV AVI), and THEN tried to render the resulting AVI file with to MPEG2 using CCE SP, I ended up with the same results as when I went straight to MPEG2 from Vegas... jagged lines everywhere. So even though it was still in AVI format when input to CCE SP, somehow Vegas had altered it so that the problem was still present.

Am I doing something wrong here? Can Vegas provide decent results with different settings? I've tried everything I can think of... resample, reduce interlace flicker, offset a second video track by 1/2 frame and 50% opacity, etc, and nothing elimates the jagged lines. Why does CCE SP handle it just fine?

Thanks all!

Comments

MCTech wrote on 3/30/2003, 9:03 PM
Are you seeing the jaggies on a burned DVD (watched on a TV monitor), or just on your PC monitor?

MainConcept Tech Support
scissorfighter wrote on 4/1/2003, 5:10 AM
On a burned DVD as well, when played in a set-top player on a regular TV, and also when played in a PC DVD player on a PC monitor.
watson wrote on 4/1/2003, 7:45 AM
You may want to ask this at the DMN form. DSE hangs there and might have some Ideas.
Cheers,
W
http://www.dmnforums.com/htm/homeset.htm
sonic foundry Vegas forum
Former user wrote on 4/1/2003, 7:53 AM
Have you by chance, changed the project setting Field Order. It should be lower field first.

Just a thought.

Dave T2
scissorfighter wrote on 4/1/2003, 7:15 PM
It is set to lower field first, although, I did try setting it to upper field first just to see if that helped. Didn't.
jetdv wrote on 4/1/2003, 8:42 PM
What is the quality slider set on? Mine defaulted to 15 but it MUST be set to the max of 31.
scissorfighter wrote on 4/2/2003, 5:27 AM
yup, set to 31.

SonyDennis wrote on 4/3/2003, 12:06 PM
Without seeing the images, it's hard to guess, but the field order question would have been the first one I asked as well. Check to make sure the deinterlace method is NOT set to "None". Is your render to an interlaced format? Are these single line artifacts? I ask because a common result of scaling interlaced footage that hasn't been deinterlaced is a moire effects where you get big blocks of interlace, tearing the image.
///d@
DDogg wrote on 4/3/2003, 2:42 PM
I closely read your post. Let's work it through one thing at a time.
"I tried experimenting some more ..."
1> Ok, so what format is the original AVI file in?
Interlaced or progressive? Framerate?

2> When you render the original file to DV format using Vegas are these jaggies there when you play it in Windows Media Player? Forget encoding to mpeg for a moment as you said the problem also arises when you encode the Vegas rendered output to CCE. This tells me it ain't anything to do with the encoder, at least at this first stage. It may be changes being induced into the footage by the conversion to DV format in Vegas. So check that part first.




scissorfighter wrote on 4/3/2003, 7:43 PM
Ok, I figured it out! Boy that was a pain in the a$$. Turns out, it had nothing to do with interlacing at all. The original video was shot on DV, and transferred via firewire into vegas capture. Interlaced, 29.97, NTSC DV. Here's the catch... the original video was shot in 16x9. Previously, when I rendered it out to mpg, I left the "Aspect Ratio" setting on the Video tab of the MC MPEG2 codec custom settings to "4:3 Display". The final video still came out in 16x9 format, so I thought I was doing things right. But I couldn't get rid of those jagged edges no matter what. So tonight, I tried a whole bunch of things and eventually adjusted the "Aspect Ratio" to "16:9 Display". This time, the video still came out in 16x9 as before, but the jagged edges were gone!! A great picture! The one thing I'm not sure of is why the video was rendering in a "letterbox" format when I previously had the aspect ratio set at 4:3 in the custom settings for the render. Anyway, it looks great now! Thanks everyone for your help and suggestions.

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