[mythtv] keyframedist discrepancy

[Craig Longman]

i've been trying to figure out why the total time on my transcoded 
recordings (converted to mpeg-4)  is always wrong, they show up as half 
as long as they actually are.  the problem seems to be that the 
NuppleVideoRecorder assumes and sets keyframedist to 30, but 
AVFormatDecoder assumes a keyframedist of 15.

which one is correct for mpeg-4 video?  the mpeg-2 stuff is 15, but that 
might just be because it doesn't handle larger gops, but i do notice a 
definite little jump in the smoother areas of the image when i use a 
size of 30.

i'm going to do some tests to see how much bigger the files get if i 
record at 15, but if someone has the definitive answer, i'd appreciate it.

also, it seems like there is now way to determine from an arbitrary file 
the keyframe distances, is that true?  it sure doesn't seem like any of 
the avcodec structures (and boy, there's a lot of them) contain one.

cheers,
 
    CraigL->Thx();