GOP Size : Small (4) or large (16)

[jfebus]

Hi All,

What are the Pros and Cons of using a small GOP size? I am using a mpeg2 capture board (Vitec DCM) and have noticed that when using the same source ( old VHS ) I get less mpeg artifacts when using a GOP size of 4, instead of the recommended 16.

Is there any problem using a GOP size so small?

Regards,

[BJ_M]

no - as long as you user a higher bit rate .. the 4GOP is common in some high end mpeg capture boards to enable easier editing later on ..

but if you are capturing and burning straight ,, better to go w/ the standard GOP

[jfebus]

Do you have any idea why I get better quality in the palyback, using the same bitrate (5000), using smaller GOP sizes?

Regards,

[Don2050]

http://pwp.netcabo.pt/0165394101/Compression.html

Go down to the section that says GOP Structure

basically smaller GOP structures use less delta frames(those frames that are just calculated differences) and result in more I-Frames(those that are actually taken from the original). So in essence you have more of the original frames and less of the assumed differences.

[jfebus]

Hi all,

I finally got a viewable DVD from my Vitec DCM card. I had to configure it to capture using a GOP size of 4.

I think there is something wrong with the card due to the fact that I can capture usinf dv firewire connection and then convert the .avi to .mpeg using mainconcept whit a GOP size of 18.

Any Ideas?

Regards,