AC90: PS vs PH recording mode

T

tengo

Active member
Hi guys, I am wondering about the image quality difference between:

PS 1080/50p (Average 25 Mbps / Max 28 Mbps)
PH 1080/25p (Average 21 Mbps / Max 25 Mbps)

What I am thinking is that if 1080/50p is recording twice the no. of frames, then shouldn't the image be worse than 1080/25p? Although there is a small increase in data bit rate, but there is also a huge increase in no. of frames (x2).

On the other hand, 1080/50p would have the versatility of slow motion in post if necessary.

Btw, Panasonic brochure says that PS mode is the highest quality for 1080.

Any real-world inputs about this? Thanks!
 
Last edited:
Yes there's twice the frames, but -- that doesn't mean it requires twice the bitrate. It's a long-GoP codec, so it only encodes the changes between frames, not the whole frames. And there's much less that can change between 50fps, and 25fps. Meaning, the change from frame 21 to frame 22 in PH will probably be a lot more than the change between frame 48 and 49 in PS. So even though there's a lot more frames, it doesn't necessarily take that much more bitrate to accommodate those additional frames.

I haven't spent too much time comparing PS vs PH, they're both pretty much at the top of the AVCHD food chain. If you think the versatility of post slow-mo would be helpful, then yeah, try PS mode.
 
Fascinating insight, .. we do PS all of the time, on the basis that "its the best", no hassles with it, ever.
 
Hi


Interesting info. Never thought of the fact that there is less movement between two frames in 50p compared to 25p and how this is affected by the codec.


I now have a question I've thought of.


I like the cadendce of 25p. I used to film a lot with my Canon XH-A1 and then I more or less always filmed in 25p.
I now have a Panasonic AG-AC160 and have the choise to use either 25p or 50p (among others of course).


My question is, what will give me the best quality if the final delivery will be 25p? Is it to film, edit and deliver in 25p all the way, or is it better to film and edit in 50p and render out at 25p for the final delivery? Does it matter att all, will there be any visible difference in quality, apart from cadence? Of course I understand that I give up the possibility to do nice slow motion.


I've done a short test by render a 50p clip to 25p. The clip contains running water with small waves and there I can see that the codec struggles with the quick movements of the water. Just wonder how it will look if I film in 25p and render out as 25p.




Regards,


/Bo
 
Well, the best way to know is to do as you've done, and test... but unless you see a significant enough difference to warrant the extra work, I'd just shoot 25 for 25 and be done with it...
 
You must log in or register to reply here.
Back
Top