Unique mp4 rendering problem

JS wrote on 7/18/2011, 1:15 AM

I've got a VMS 10, standard def project with horizontal title crawls (Vegas generated media) that appear in a chroma keyed section of a still image. I've rendered to MPEG-2 and WMV, and the words move smoothly. But when I use Sony AVC mp4, the words stop and start as they move across the screen. A Main Concept mp4 render gave me movement that was more even but not at all smooth.

I tried rendering with the chromakey disabled and the level of the still image lowered so I could watch the titles underneath, and the movement was still jerky. Then I rendered the titles alone and cut out the still image--and the problem went away. But the image is a 627kb jpg--way too small to jam up the software. What am I missing?

Comments

musicvid10 wrote on 7/18/2011, 8:51 AM

System specs?
Project Properties?
Render Properties?
Playback Device?

amendegw wrote on 7/18/2011, 12:10 PM

Two more:

Bitrate of render?
Framerate of render?

...Jerry

Edit: Whoops! I guess that will become clear with "Render Properties" I suggested those two settings because I've seen stuttering with too high a bitrate (the workstation/player can't keep up) or too low a framerate (59.94 fps will play more smoothly than 29.97 fps which will play more smootly than 14.985 fps)

JS wrote on 7/18/2011, 2:56 PM

System specs?
Old PC: Pentium 4, 2.4Ghz, 1.2G RAM, generic video card—but I have used it to make very good mp4’s.
Project Properties?
640x480, 29.97, progressive scan, PAR 1.0, Best quality, interpolate fields
Render Properties?
For Sony AVC: 640x480, Main profile, Cabac, 29.97, progressive scan, PAR 1.0
Bitrate of render?
I’ve tried everything from 768,000 bps to 20Mbps (Actually, the problem largely disappears at 768,000—but then the quality suffers.).
Playback Device?
WMP, Quicktime, VLC, Vegas—I play every test render on every device. There are small variations, but essentially the results are consistent among the devices.

I checked another part of the project with ordinary Vegas titles that crawl vertically across a still image (no chromakey)—the movement in the Sony AVC render was OK, but it was better in WMV.

Could it be relevant that the titles were originally created in Vegas 7?

amendegw wrote on 7/18/2011, 3:15 PM

"Old PC: Pentium 4, 2.4Ghz, 1.2G RAM, generic video card—but I have used it to make very good mp4’s... I’ve tried everything from 768,000 bps to 20Mbps (Actually, the problem largely disappears at 768,000—but then the quality suffers.)."My opinion... your PC doesn't have the horsepower to playback the mp4s at a bitrate that will produce adequate quality. I can't be positive of that, because I don't have a 2.4Ghz P4 to test on, but here's something you can do: try rendering at 2Mbps, load the Media on a USB drive and take it to a faster pc (dual core, Quad Core or i series), and see if it doesn't play more smoothly.

...Jerry

PS: You might be able to get smooth playback on your current workstation if encode your mp4s using Handbrake. We've discovered it produces better quality at lower bitrates (search this forum for "Handbrake").

MSmart wrote on 7/18/2011, 3:36 PM

I’ve tried everything from 768,000 bps to 20Mbps (Actually, the problem largely disappears at 768,000—but then the quality suffers.).

So does everything else about the video look good at the higher bitrates, just not the keyed rolling text?

musicvid10 wrote on 7/18/2011, 6:01 PM

You have a single core machine. That's almost a slam dunk for choppy playback of AVC..
You might try your final render in Handbrake instead. It seems more "playable" as a delivery solution.
Start with our suggestions here, altering the properties to suit your source and render size.

JS wrote on 7/19/2011, 2:02 PM

Thank you for your comments. Clearly my computer is behind the times; and I was able to use Handbrake to turn a jerky render into a smooth one. BUT…

A couple of weeks ago I rendered a project to mp4 with Sony AVC (5Mbps)--no titles, but lots of effects—and it plays beautifully, especially on Quicktime. (Weirdly, I tried rendering a bit of that project to WMV and the playback was horrible.) Plus, MSmart, yes, the rest of the current project (rendered at 4Mbps) looks pretty good. I don’t have a problem with mp4’s in general—I have a problem with one particular sequence. Perhaps I’ve stumbled across some odd combination of elements that shows up all the shortcomings of my computer. In any case, thanks again for your advice.