Understanding the HVX Scan modes 1080i/30p,1080i/24p, 720/60p...

D

DP StrangeLove

Well-known member
Hi, I probably can assume that this subject has may been discussed before, but I am new to the DVX/HVX world, and haven't yet found a clear definition of what these scanning terms mean. I am coming from the world of the Canon Xl1. I will hopefully have my HVX at the end of this month, and will be jumping immediately into a commercial production with the new cam, so I want to get up to speed on what all of the scanning terminology and different modes of the HVX mean.

A few questions off the bat, I don't quite understand the 1080i/30p/24p modes. For instancce, does 1080i/30p mean that the camera starts off recording at 1080 interlaced, and then from those interlaced frames does it make a 30p signal? And what does the 30p or 24p mean? Is that how many times the camera scans the image per second? How is this different from frames per second? Is it different than frame rates? And then if the camera can also be overcranked and undercranked, why aren't modes such as 720/12p, or 720/80p listed? And also, does the HVX have variable shutter speeds like my Xl1?
Lastly, am I just making this all too confusing? Please help....
Thanks!
Ben.
 
hmmm...over 57 views and no responses. someone has to know and want to explain. Isn't this what this helpful community is all about?
Well, I may as well add to my questioning then, I was also curious about how the pull-down relates to this. How a 2:3 pulldown is different from a 2:3:3:2?
 
I'm new to all of this too, but I'll try to answer as best as I can (someone more knowledgeable correct me if I'm wrong please)!

I'll try to go through your questions one by one...

30p means 30 full individual frames will be played back per second. There is no interlaced to progressive conversion involved. Same deal with 24p. This is different to the number of frames that are captured per second. For example capturing at 20 frames per second with a playback frame rate of 30 will give you a slight fastmotion look; as 20 frames are captured per second but 30 are played back. Hope that makes sense! Modes such as 720/12p aren't listed as they are not a timebase (playback frame rate) like 30p or 24p. Instead, they indicate the number of frames captured per second, as I mentioned above. And yes, the HVX has fully adjustable shutter speeds as far as I know.

I probably got a lot of the terminology or actual technical process mixed up in my explanation, but it should hopefully be sufficient for you to understand what the concepts are! :)
 
alpha54 said:
I'm new to all of this too, but I'll try to answer as best as I can (someone more knowledgeable correct me if I'm wrong please)!

I'll try to go through your questions one by one...

30p means 30 full individual frames will be played back per second. There is no interlaced to progressive conversion involved. Same deal with 24p. This is different to the number of frames that are captured per second. For example capturing at 20 frames per second with a playback frame rate of 30 will give you a slight fastmotion look; as 20 frames are captured per second but 30 are played back. H :)
Click to expand...

Thanks for your help, it cleared something up, but I think you answer just touched on what I already know. Here is what I don't understand, maybe I should have stated my questions more clearly. I understand how varying the capturing a certain frame rate, and a playback will affect the perceived speed (ie under/overcranking).
What I am a bit confused about is the scanning procedure. For instance, why is it 1080i/30p how can it be progressive, (the 30P based timeline)playback if the 1080i is interlaced? If as you say the 30p means 30 full frames wil be played back per second, then how is 720/24p different than 720/24pn (native progression) If it always means full frames will be capture then how is native progression any different?
Whewww, I think I have totally twisted all of this up like speghetti, but without the sauce.
And how
 
Perhaps a google search would help? I don't have time to for a complete explaination but the 2:3 and 2:3:3:2 are the schemes used to duplicate say a 24p stream on a 30p playback meaning some frames are duplicated.
 
js33 said:
Perhaps a google search would help?
Click to expand...
Try http://www.ebu.ch/en/technical/trev/trev_301-editorial.html .

As regards variable frame rates, then try to envisge that whilst on playback 24fps are read OFF the card, they will be recorded ON to the card at whatever fps speed is set (with corresponding shutter speed). Obviously, if the two don't match the action will be speeded up or slowed down. Exactly the same as film.
 
Last edited:
Your link didn't answer his question about 3/2 pulldown. Your link assumes he is in PAL land which he obviously is not if he is asking about pulldown.

Pulldown explained.
http://www.cybercollege.com/conversions.htm

Complete course on video and TV production - Good read for newbies. Covers alot of ground.
http://www.cybercollege.com/quicksrt.htm


Also Google is your friend. Take a man searching you feed him for a day. Teach him how to search you feed him for life.
 
Last edited:
js33 said:
Your link didn't answer his question about 3/2 pulldown. Your link assumes he is in PAL land which he obviously is not if he is asking about pulldown.

Pulldown explained.
http://www.cybercollege.com/conversions.htm

Complete course on video and TV production - Good read for newbies. Covers alot of ground.
http://www.cybercollege.com/quicksrt.htm


Also Google is your friend. Take a man searching you feed him for a day. Teach him how to search you feed him for life.
Click to expand...


..so you're calling me a newbie, eh? just joking, thanks for the link, made everything seem so simple. The only thing I am still curious about is the difference between a 3:2 pulldown and the 2:3:3:2 pull down....
 
Works fine for me.

Basically it comes down this:

3:2
- Requires the computer to Recompress the media to make a 24p clip.
+ Looks smooth on a 60i monitor

3:2:2:3
+ The computer can just discart the 6 blended frames every second to get 24p without recompression.
- Does not look smooth on a 60i monitor.
 
Andres, thanks got it to work. very helpful
So basically I will be using 3:2 when shooting 24p but editing for a video output, a 30frame based timeline. And use 3:2:2:3 for a film out. right?
 
pdf that explains very well

pdf that explains very well

by chance i just stumbled across this , and i now know the difference between the pull downs...

http://www.sonymediasoftware.com/download/step2.asp?DID=511

direct to the PDF = http://www.sonymediasoftware.com/download/Step3.asp?URLID=2128&SerialNum=

ive been watching some of the sci-fest movies...and most of them seem very
jerky in their motion , and if that what the 24p does then i think it looks awful.

so i went looking for some info on it and found the link.

cheers
 
You would use 3:2:2:3 when you want to edit in a 24p timeline.
That could be for Filmout or DVD as the DVD standard supports 480p24, the DVD player will create the pulldown on playback. 480p24 mpeg is much cleaner than 480i60 with pulldown, and can be created by most Mpeg encoders.

It's always possible to add pulldown in any modern NLE. FCP can do it on the fly when playing back a 24p sequence. So even for 60i Tapemasters it's usefull to shoot with 3:2:2:3.

3:2 is mostly there for compatility and if you want to save time in the NLE (or if the NLE does'nt support 3:2:2:3 removal and 24p editing)
 
You must log in or register to reply here.
Back
Top