Relationship between Mpg and Avi?

[jimmyjojo]

I use Tmpgenc. I capture D8 movie onto comp in avi. Then I convert to mpg2. However, when I convert, the mpeg file is ALWAYS a fraction of the avi file. For example; 5gig Avi would convert into a ~1gig Mpeg. And the resulting Mpeg quality would be far inferior to the original captured avi. Is this usual? I always read on random forums that mpegs are generally larger and avi's are smaller.

I normally set the bitrate to 8000 also. Does anyone know the general theory/relationship between avi and mpeg? Or am I doing something wrong?

[jimmalenko]

I think what is happening is that you are capturing to AVI with either a small compression codec or uncompressed. When you convert to MPEG2 a codec is applied which trims the filesize. The size of the MPEG depends on the quality in kbps. In general, AVI codecs achieve better compression than MPEG. Quality can be another story.

[BJ_M]

there are over 50 types of avi files of varable quality-- so its an open ended question ..

in your case you are using DV 5:1 compression avi and converting to mpeg -- which at 8000 bitrate will be smaller ... if properly done , it should none the less be almost the same as the avi quality -- or extremly close on visable inspection while playing ... the kicker is: how is it encoded and by what and all the other settings ..

[BJ_M]

I............. In general, AVI codecs achieve better compression than MPEG. Quality can be another story.

not true -- depends on what type of avi -- as avi is just a wrapper (same as quicktime)

[jimmalenko]

not true -- depends on what type of avi -- as avi is just a wrapper (same as quicktime)

Let me clarify this by saying IMHO that this is the case for MAINSTREAM AVI codecs such as DivX.

[BJ_M]

i guess you could say that for home use -- for mainstream use in pro use -- divx/xvid doesnt get in the top 50 -- so i dont consider it much ..

but divx popularity is certainly rising ...