Exporting video for iPod - audio OK but video is "white"

Question

I know this issue has been raised before but I cannot find a clear resolution anywhere - happy to be pointed to the right place.
Some time ago I converted some old VHS home movies to DVD and they play fine. To view them via AppleTV I've converted them to MP4 using H.264/AAC via MEGUI, and they work fine in iTunes on the PC and on AppleTV.
Once they were in iTunes I tried converting them for iPod but the output is a blank white video screen though the audio is fine.
To diagnose the problem I tried loading the MP4 version directly into Quicktime (Version 7.6.8)where the play fine. Then I tried exporting them for iPod and I get the same white screen plus audio.
I've seen this issue dismissed as due to some form of DRM but I doubt that is the case here. The video is my own, the DVDs I created are not CSS protected and the MP4s are also unprotected.
I've also seen it attributed to a missing codec, but that is unlikely given both iTunes and Quicktime play the videos without a hitch.
Any clues on how to proceed?
John

Answer 1

Last post before I leave things alone for a while.
I've uninstalled and reinstalled iTunes and Quicktime and iTunes no longer chews up lots of CPU when trying to convert one particular Quicktime created file.
I've also recreated each file again from the same source, the AVI encoded as DV-PAL with screen res of 720x576. I created a series of test cases to try to pin the problem down and I think the best exposition is the following -
The problem
An MPEG4 file exported from Quicktime loads and plays in iTunes, plays on AppleTV and can be converted for iPod.
An almost identical MPEG4 file created by MEGUI using the x264 encoder, latest build 1649, and all the same settings as Quicktime loads and plays in iTunes, plays on AppleTV but when converted for iPod produces a file with audio but the video is "white". Looking at the file size, less than 2mb, it is pretty obvious that the video stream is simply not there.
Clues
Quicktime Movie Inspector reports the screen resolution of the file it exported as 720x540 while for the MEGUI created file it reports a very odd 787x576. Note that Windows Media Player and YAMB (MP4Box utility) both report this same file as 720x576 which is what I would expect as MEGUI did not resize the video. As an aside, WMP and YAMB also report the Quicktime created file as 720x540 so they agree with Quicktime on that score at least.
Obvious Question
Why does Quicktime report an incorrect screen resolution, and is this contributing to the conversion problem in iTunes?
My understanding is that MPEG4 uses 16x16 macroblocks and so the dimensions of anything to be encoded must be in multiples of 16 and 787 is not a multiple of 16.
Of course, the 787x576 screen resolution could be a red herring.
Details from Quicktime Movie Inspector follow:
File that converts successfully
Source: scene0005c created QT as MPEG4.mp4
Format: AAC, Stereo (L R), 48.000 kHz
H.264, 720x540, Millions
Movie FPS: 25.00
Playing FPS: 25.00
Data Size: 31.32 MB
Data Rate: 2.39 mbits/sec
Current Time: 00:00:00.00
Duration: 00:01:49.84
Normal Size: 720x540
Current Size: 720x540
File that does not convert successfully
Source: scene0005e created MEGUI as MPEG4 AAC-LC 320Kbps.mp4
Format: H.264, 787x576, Millions
AAC, Stereo (L R), 48.000 kHz
Movie FPS: 25.00
Playing FPS: 25.00
Current Time: 00:00:00.00
Duration: 00:01:49.89
Normal Size: 787x576
Current Size: 787x576