Hidden footage in Quicktime

[Harp]

sorry if this is an old topic.

So I'll play a video in quicktime and everything seems fine, but then after the video stops, I'll move the slider back and what I will find is completely different footage of the same video than what I just watched. Not sure how else to describe that. It's like the footage was somehow hidden in the other footage.

I'm using QT 7.1.2 on an intel macbook pro. os x v10.4.7.

I've come across this so far only with mpegs but I can't say yet that it's that specific.

I've played the same files with VLC and they play out fine all the way through (with all the footage) but have little blips where the 1st version and 2nd version cross.

Sorry if I'm not very good at explaining this. Just wondering if someone has an explanation.

 

[eonxl]

i think i've experienced this too. although i think what i'm seeing is video from a previously viewed file. i think that if you view multiple files within the same session (ie. without quiting qt in between), then the previous file can sometimes show up when moving around within the current video.

anyways, that's what i think happens.

--e

 

[Harp]

no, this is definitely the same files. And it always does it at the same places as well.

I want to say that it's something wrong with the files because they are jumpy in VLC also, but I shudder to think it might be something in my cpu. Maybe an update will tell.

 

[Mikuro]

Sounds like this file was created by either combining two MPEGs or splitting one. I've never noticed this in MPEGs myself, but I've noticed similar problems with AVIs and other media types. The problem (I think) is that you can't easily cut video from any given point; you need to start at a 'key frame' (a key frame is a frame that is entirely self-contained, like a JPEG, instead of a frame that is based on data from other frames). If you try cutting it at the wrong place, either at a non-key frame or in the middle of a frame, weird things will happen.

I don't think it's anything to worry about. QuickTime's MPEG support is notoriously non-error-tolerant. VLC is very error-tolerant, but the skipping sounds perfectly normal for a slightly-corrupt file.