Quicktime won't open mpg files

Question

I am trying to create a DVD with chapters/scenes from a single .avi file that won't open in Quicktime (nor iDVD nor iMovie).  It's the basic QT, not pro.  I can convert the .avi file to .mpg (using Burn or other tools), but the resulting file (.mpg) won't open in Quicktime either.  Seems if it won't open in Quicktime, it won't open in iDVD or iMovie, where I'd hoped to include chapter markers and menus. 
Since this was created by Burn on my Macbook, I'd expect the resulting .mpg file to be readily useable by Qucktime, but it isn't.  Can someone first explain why QT won't open the file (VLC will open it), and second what other approach I might use?
Thanks!

Answer 1

OK, again, I'm not using the avi file, but the mpg that was created by Burn from the avi file, so I wonder if the original is so "muxed up" as it might seem.  No mpg inside of an avi, if I understand you both correctly.  The original AVI is thus far MIA though I do think I burned it to a data disc.
Having the original AVI would let see what compression codecs were used to create it, how compressed the video was, see the encoded dimensions/display dimensions if PAR encoded, and give us some idea as to how much visual quality may have been lost in transcoding the AVI to MPG, as well as, save you one level re-compression if you were then able to start your work flow with the original source file. Too bad you can't find it.
"Muxed" in the case of your MPEG2/MP3 MPG file refers to the fact that the audio and video content is broken into blocks of video data which are interspersed with blocks of audio data in a single data stream to provide synchronizarion. QT files, on the other hand, contain up to 99 tracks of audio, video, and/or other forms of data the playback of which are all sybchronized to an external clocking system and is the main reason your MPG file is not natively QT compatible,
To play MPEG-2 content, whether in an elementary or a multiplexed stream, in a QT based application, you must first purchase and install the Apple QT MPEG-2 Playback component ($20). Even then, for any of the unsupported audio compression formats you would need a secondary application like MPEG Streamclip (free) to bridge the spatial to temporal synchronization problem to make it compatible Apple QT-based applications like QT, iMovie, GarageBand, iDVD, etc. So, if you plan to use the MPG file as your source file, you will either have to purchase the MPEG-2 component or use a third-party application work flow.
All that said, I think I'm understanding how to go about this now.  Oddly, I do have Perian installed (I think because I once had a similar problem and had hoped it would help) and it's up to date.  It does not seem to fix my problems though.
This is why you need to pay attention to the actual codecs used in the AVI file and ensure that you have removed any third-party components which may conflict with the Perian component package as detailed on the support page of the Perian web site.
I'm using this file to try to learn a little about iDVD and iMovie (after all these years of using Macs!), so I had hoped to take these first steps without buying a commercial product.  I don't mind spinning my wheels trying different workflows so long as I'm learning and have options.  Garageband is an interesting idea as I had no idea it would handle video files.  Perhaps Audacity would also do the trick?  I don't have any need of creating markers at any particular points in the file, just something to ease the process of moving from one place to another in the video.  Markers at an even time interval would be fine, and I'd love to create a menu that allows navigation, though even that isn't crucial.
To learn more about iDVD, use help file, view the tutorials, and visit the iDVD forum. However, before you can do anything in iDVD, you will have to convert your MPEG2/MP3 MPG file to a QT compatible compression format. On my system, I would simply open the MPG file in MPEG Streamclip (which already has the Apple QT MPEG-2 Playback component installed) and convert the MPEG-2 video to AIC (Apple Intermediate Codec) and the MP3 audio to Uncompressed audio. The resulting MOV file will then import to any Apple QT-based edit/conversion application on your computer (assuming the source file and your software is in proper working order).
I may end up trying Toast as I've considered it in the past and my needs aren't very sophisticated.  But being largely without work and mostly self-employed these last two years has made me a bit of a miser...
Toast should save you the cost of the MPEG-2 Playabck component but does cost much more than the $20 component. I am still using Titanium Toast 10 Pro but it may be aout time to upgrade to 11. It is a really good general purpose conversion/authoring appliction for all forms of target optical media.