View Full Version : Sony 12f GOP, Canon 6f GOP. is it true?
daktulus
10-30-2006, 01:02 PM
I´ve read Sony uses for all HDV 1080 cameras a 12frame GOP (meaning only every 12th picture is real) vs Canon using 6frame GOP.
Is it true?
Is there any difference when filming fast moving objects and panning?
Huy Vu
10-30-2006, 01:04 PM
Isn't Sony 15 frame?
meta4
10-30-2006, 01:43 PM
I too have heard of the 6 & 12 difference, which may explain why sony HDV breaks down easier with motion artifacting situations.
Truly though, I'm not sure how they'd do this, Canon would be storing twice as much P-frame (is it 'P') information per second of footage. Yet they both compress to 25mb/s
Strange, but yeah, I've heard this too.
daktulus
10-30-2006, 04:55 PM
Anybody else?
Any confirmed information?
Barry_Green
10-30-2006, 05:49 PM
Sony = 12GOP in 50Hz territories, 15GOP in 60Hz territories.
Canon 1080/50i must be 12GOP or it wouldn't work in Sony decks.
Canon 1080/60i must also be 15GOP or it wouldn't work in Sony decks.
Not sure about Canon's 24F/25F/30F, those are proprietary formats to Canon.
It's JVC that uses the 6-picture GOP.
Elton
10-30-2006, 11:04 PM
Canon has never specified the GOP structure of their HDV implementation. Barry's probably right about 1080i modes.
The main reason the F modes are more artifact resistant is that they are progressive images fed to the encoder, which is easier for MPEG2 to deal with than interlace.
epicedium
11-01-2006, 03:19 AM
Elton- does that mean that the XL-H1's famed codec advantage over the Z1 is limited only to the F modes, not the interlaced?
Elton
11-01-2006, 07:41 AM
No, Canon 1080i is a bit better than a Z1 under duress too. Even though the GOP # might be similar, that doesn't mean that all encoders are created equal. I suspect it's a combination of factors that make Canon's imagery noticeably less artifacted.
Hopefully I'll find out the GOP story from some Canon reps next week.
epicedium
11-01-2006, 10:13 AM
Thats cool, just checking .. your post had me worried :)
I'd imagine that DIGIC is partly to thank-- the easiest way to improve mpeg2 quality is to throw more processing power at it, allows you to use the more expensive algorithms, obviously! Sony have no lack of understanding of how to do mpeg right, so I find it a little hard to believe they just messed it up ... my guess is that they packed the cams with relatively cheap chips...
Bogdan
11-01-2006, 08:56 PM
No, Canon 1080i is a bit better than a Z1 under duress too. Even though the GOP # might be similar, that doesn't mean that all encoders are created equal. I suspect it's a combination of factors that make Canon's imagery noticeably less artifacted.
I agree. It comes down to algorithm and performance. In-camera encoding is real-time process heavily dependent on processor speed. Performance really matters when time is so limited. Better efficiency of the processor and algorithm can improve interpretation of fast changes between adjacent frames. The result: less or almost none artifacts in extreme motion.
HDV has been blamed by many for artifacts, but Canon's implementation is the best in the class, imho.