AVI Resolution vs. Mpeg2 Recovered from Old Forum

[jchunter_2]

This test shows that video image resolution is the same in the AVI and Mpeg2 files after one rendering and also after 8 edits and re-renderings.”

Both files were rendered using NTSC Mpeg 2 at the same Variable Bitrate (8264 kbps), 720X480, Square pixels, Best Resampling Quality, Keep Aspect Ratio, 4:3, 100% Compression Quality.

Procedure:
I created a new video resolution test file that was designed to force a complete re-encoding of every other GOP (Group of Pictures) at a different point within each GOP. Two different Resolution Test Patterns were alternately placed in the timeline and the duration was set to 0.9 seconds.

The project file was first rendered into two 11 second video files: One AVI Type 2 and the other Mpeg2. Both were rendered with the same properties wherever possible.

The two files were then subjected to eight consecutive alternate edits and re-renderings. Editing consisted of clipping off a few frames at the beginning of the file (with Save Trimmed Video) or by chopping into 3 pieces and deleting the middle, using Multitrim-Video. Each time an edit was done, a new video file was created. The new file replaced the prior file in the timeline and then the process was repeated. The AVI file was converted to Mpeg2 after the last edit.

Results:
I compared the first rendered files to the last re-rendered files using Windows Media Player version 9 and with VS8.01 in Share/Project Playback. There was no visible deterioration of the images after 8 re-renderings in either file type. If there is deterioration, it must be so small that it is not visible at 720x480 pixel frame resolution.

Some Observations:

The AVI files shimmer and squirm when played back in WMP and look blurry in Video Studio Share/Project Playback. (IMHO, this should be considered a bug in VS8.01.) However, after conversion to Mpeg, they look fine in playback.

The AVI files were about 8 times larger than the Mpeg2 files.

The third and sixth test pattern images in both avi and mpeg2 videos showed slightly lower resolution than the others. This was seen after the first rendering and also in the last. This must be an artifact introduced by Video Studio – perhaps in response to the structure of the test video. The magnitude of this loss of resolution exceeded the loss of resolution between the first and last renderings of either file type.

I hope that someone else will take the time to try to replicate this test.