How do I get a close replica of a .mpg movie?

Question

I'm playing around with QT PRO when I get a bit of spare time now and then, and I thought I'd try some editing. Downloaded the first ".mpg" file I came across on the net, and these are it's specifications:
Data Size: 10.9 MB
Format: MPEG1 Muxed, 320 x 176
FPS: 25
Data Rate: 1394 kbits/sec
Size: 320 x 176
Duration: 1.06
When I tried to edit, it didn't have those white crop handles, so I thought I'd export to see if they appeared. They did, but no matter how I exported, the export version of the movie was significantly different in contrast or colour or sharpness. I've tried "no compression", "best quality", "same FPS", altered the contrast, the brightness, the colour spaces, the sharpness; experimented with bit rates from 2 Mbps to 8 Mbps; several different formats; even exported as 1700 separate tiff files and made a movie of them, but still the movie was inferior to the original.
The original move is a shocker in terms of quality. That doesn't matter, I'm just experimenting. The thing that amazed me was the export versions were always worse. I realise that the movie was probably compressed by a factor of 30-100, so something has to give, but I've never seen such degradation in quality when playing around with jpeg images, or mp3 music files; meaning if I take an atrocious jpeg and convert it to tiff, it is simply an atrocious tiff, not an even-worse tiff.
Any suggestions as to the method I should use to ensure that when I export this atrocious-quality file, it is not even more atrocious? It doesn't matter if it ends up as 25 GB, I'd just like to find out how to export with NO loss of quality.

Answer 1

Guy Burns:
As you can see you can't a MPEG in Quicktime. MPEG (usually) denotes either a MPEG-1 or MPEG-2 video file. MPEG-2 video are used mainly in DVDs. There are other applications that MPEG-2s are used for,for example, in broadcasting of TV shows. MPEG-1 video were very popular ten years ago. They are still popular in the Asian counties. MPEG-1 videos are very heavily compressed videos and uses a small dimension for the video.
When you exported the video to another codec you picked codec that are not as compressed as the MPEG-1 codec. Thus making the video bigger in file size. Using another codec doesn't always mean a better looking video from the original video. If you don't need to edit that MPEG-1 video there's no need to export to another video format. But, if want to edit the video you can use a free program called MPEG-Streamcilp to edit the video in:
http://www.squared5.com/
As for key frames here is a definition of what keyframes are:
From Apples web page about H.264...
c. Key Frames: Many compressors use “frame differencing” to compress moving images. Frame differencing is the process of determining what information has changed from a starting frame (called a “key frame”) to subsequent frames. The key frame contains all of the information for an image. Subsequent frames contain only the information that has changed. Depending on the compressor you use, you can specify how often you want key frames to occur. If you don’t have enough key frames, the quality of your movie might be lower because most frames are generated from others. On the other hand, more key frames result in a larger movie with a higher data rate. With some compressors, an additional key frame is inserted automatically if too much of the image has changed from one frame to the next. A good rule of thumb for general use is to have one key frame every 5 seconds (multiply the frames per second by 5). If you are creating a file for RTSP streaming and have concerns about the reliability of the delivery network (as with the public Internet), you may want to increase key frame frequency to one key frame every 1 or 2 seconds. To leave the key frame interval up to the compressor, select Automatic. For H.264, we recommend leaving the key frame interval up to the compressor; so you should choose “Automatic” for the best quality result.
Here's the URL to the whole article about using h.264 and what the settings mean for h.264 in Quicktime:
http://www.apple.com/quicktime/tutorials/h264.html
Here's two articles about MPEG-1 and 2:
http://en.wikipedia.org/wiki/MPEG-1
http://en.wikipedia.org/wiki/MPEG-2
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