An MPEG-2 is an MPEG-2 ?

ChristerTX wrote on 1/19/2004, 4:10 PM
On the size issue:

A rendered MPEG 2 file in Pinnacle is smaller than a rendered MPEG 2 file in Movie Studio. (Same AVI source is used for comparison)

Why is that ?

Is'nt the MPEG-2 a standard compression format or could different programs create a MPEG-2 with different compression?

Is there such a thing as a un-compressed MPEG-2 file?

(I have Sony's GigaPocket and I suspect that it produces a un-compressed MPEG2 file as teh file is very large in the highest quality mode.)

Comments

obiron wrote on 1/19/2004, 4:53 PM
ChristerTX ,

Probably the biggest difference is in the bit rate. The higher the bitrate the bigger the file and the better the quality.

MPEG2 is a standard but lots of factors can cause different file sizes even in the same software; bitrate likely has the biggest impact.

MPEG2 is compressed. Furthermore, it is lossy compression meaning that data can be optimized away because the dynamics of the video stream allow the algorithm to leave out certain details but recreate the original pretty closely. So, if you try to re-create the avi from which the mpeg was generated you can never get the exact original file back. It will be close but ...

Your GigPocket file will be large in the highest quality mode because in that mode it is using a higher bitrate;

You don't give any sizes from which to compare, but miniDV video in avi form is approximately 13 GBytes per hour. Encoding an hour in MPEG2 is approximately a 10:1 compression so the MPEG2 file will be around 1.3GBytes. Don't hold my feet to the fire on those numbers 'cause lots of things can cause the file size to vary as I've indicated above.

Hope that helps some

Ron
Former user wrote on 1/20/2004, 6:39 AM
It will also make a difference if the MPEG is encoded using a variable bitrate as opposed to a fixed bitrate.

Dave T2