MPEG Optimizer

Berzelius · Post by **Berzelius** » Wed Oct 03, 2007 10:59 am

As part of my VS11 earning process I've been looking at the use of the MPEG Optimizer. I wonder if anyone can answer he following questions? These relate to a small test project consisting of 4 small MPEG-1 clips from my digital camera. They all have the same properties: 640x480, 24 bits; 25.000frames/sec; Data rate - Variable bit rate.

1) The Ulead tutorial considers the case of a project with a MPEG-4, a MPEG-2 and a WMV clip and states that: It is important, however, to have at least one MPEG-2 file in order to use MPEG Optimizer. As my test project consists solely of MPEG-1 files does this mean that there is no benefit in using the MPEG Optimizer - it seemed quite happy to have a go at my little project.

2) On my project the MPEG Optimizer gave, for the Optimal project settings profile, MPEG-1 (640x480 - 2903 kbps) with a Total saving time of 39.85%. Again, taking into the account the lack of MPEG-2 files, is the use of MPEG Optimizer worthwhile or, alternatively, would it at least do no harm?

3) The Timeline segment layout shows a little over half needing to be Re-encoded (red) and the remainder as Original (green). As all my clips have exactly the same properties why is this? I'd have assumed that it was either all one or the other - why the mixture?

Clevo · Post by **Clevo** » Wed Oct 03, 2007 11:19 am

Some interesting questions there.

with 3) I suspect that if it's variable bitrate it would use the clip with the highest variable average?

Just taking a wild guess there!

Berzelius · Post by **Berzelius** » Wed Oct 03, 2007 11:41 am

My apologies: I made a small, but possibly important, mistake in my original post. The Optimal project settings profile should have read MPEG-1 (640x480/ VBR - 2903 kbps). Does VBR stand for Variable Bit Rate? If so, is the 2903 kbps some sort of maximum, minimum, average or what?

Clevo · Post by **Clevo** » Wed Oct 03, 2007 1:15 pm

Berzelius wrote:My apologies: I made a small, but possibly important, mistake in my original post. The Optimal project settings profile should have read MPEG-1 (640x480/ VBR - 2903 kbps). Does VBR stand for Variable Bit Rate? If so, is the 2903 kbps some sort of maximum, minimum, average or what?

I'm not entirely sure but my understanding of VBR is that it's an average...as some scenes in a clip will require higher bit rates (fast moving objects) and other sections only requires a lower bit rate.

It could also mean the maximum...and the variable is anything up-to and including the VBR 2903.

Might go google that now.

Wikipeadia says:

Variable bitrate (VBR), or less commonly variable bit rate, is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate (CBR), VBR files vary the amount of output data per time segment. VBR allows a higher bitrate (and therefore more storage space) to be allocated to the more complex segments of media files while less space is allocated to less complex segments. The average of these rates is calculated to produce an average bitrate for the file that will represent its overall sound quality.