Strange "artifacts" in H.264 encoded video

[jackfalbey]

Beginning at 0:37 in this video you can see what I'm talking about. The frame flash at 0:53 is something that I've noticed happens some of the time when I apply a cross-dissolve to a clip that's been stabilized with Mercalli, so I'm not concerned with that at this time; just the strange pixelated/blocky stuff...

First, a brief summary of my workflow:
Capture DV from MiniDV tapes with WinDV.
Import AVIs into a new PPro project set up for NTSC standards.
Create an "editing" sequence where I do all of the trimming, color correction, Mercalli, dissolves, etc.
Create an "assembly" sequence and drop the editing sequence onto it, then add music WAV & narration recorded in Audacity (also as WAV).
Preview & encode for Vimeo (H.264/AAC, 640x480, square pixels, 30fps, CBR 1800kbit/sec, deinterlaced).

The pixelation doesn't appear in the source clips, either when viewed with WMP or from the PPro timeline in the "editing" sequence, but when I play back the "assembly" sequence it appears at different random places. If I export to AVI it doesn't show up in the resulting video, but it does in the H.264 version. I've used the same specs for other Vimeo videos and never had a problem, and because it appears in the playback window of the "assembly" sequence I don't think it's caused by the encoding. I've tried dropping the "editing" sequence onto a new & different sequence and it still occurs, so something must be happening as a result of the nested sequences, but I've used nested sequences a lot, and on much larger videos, and never had this problem... also, when I tried to open the project this morning, it said the file was damaged and couldn't be opened. I went back to the last autosave (I have it set to autosave every 2 minutes, yes I'm a bit paranoid about losing my work!) and it opened normally but the pixelation is still happening as before.

Any ideas?

[jackfalbey]

BTW, this project was started before the Font Meltdown which led me to do a clean install of XP and CS3 on my C: drive... all of the video files, project files, scratch disks, media cache, etc. were on a different hard drive, but could that have something to do with this pixelation issue anyway?

[Bill Hunt]

Jack,

One question: have you done a frame capture of the offending 00:37 frame? I kept trying to hit Pause to get a look at it, but missed a dozen times.

I've not seen such, but then have used H.264 infrequently. I'd highly recommend posting this to the Adobe Premiere CS3 forum with the link. There are a lot of heavy users of H.264 there. If you can get Dan Issacs to weigh in, you'll very likely get quick resolution. If you post, I'll comment that Dan needs to reply, to get him interested.

Good luck,

Hunt

[jackfalbey]

Thanks Bill. Yes, I'll do a frame grab and post it over at Adobe. I'm just accustomed to starting here at Muvipix for tech help.

[Bill Hunt]

I understand. I tend to start there, then move over here. It's what one is used to. Also, with my limited experience in H.264 I have no clue for you. Based on many prior discussions there, I feel that someone will have something to offer. I'll keep watching and see if I can wake Dan Issacs, Harm Millard or Jim Simon up. They always have some useful info.

Hunt