Is 720p30 really progressive?

Joe Russ · July 8th, 2003, 10:53 PM

it seems like a playback issue because i dont have an hd screen and have been watching it on the computer (no upconverting or downconverting) and i dont see any of this double image/ghost image stuff, other then the obvious blurriness from 1/30th shutter speed

Michael Hyun · July 8th, 2003, 10:58 PM

this is an interesting development.

this may mean that the jvc is actually more flexible than i originally thought.

thanks joe for sharing that with us. i haven't captured any of my footage yet....

this may actually be the best news i've heard yet ^^

David Newman · July 8th, 2003, 10:58 PM

Basically there isn't a capture problem with the camera -- it shoots true 30p. I don't play images directly off the camera (I don't know what that looks like), but the data that comes across firewire is exactly as it should be.

Steve Mullen · July 8th, 2003, 11:05 PM

<<<-- Originally posted by Michael Hyun : if this is merely a camcorder playback issue, then theoretically the playback should be fine when other HD playback devices are produced. -->>>

The problem is that both the DVHS and HD10 playback to video looking this way. That's how folks will see your work -- not on computer screens. Often very big screens. The displacement of the 2 images is 6-inches!

We really need someone who also owns a DVX100 to shoot some 30p of moving cars and people. Is this a visual phenomena of all 30p? Or, is it it a function of a funky JVC rate-converter?

Joe Russ · July 8th, 2003, 11:14 PM

i think its the output from the camera itself. and actually, my stuff will all be down converter to anamorphic dvd resolution and displayed at 24p, so, it doesnt matter what the camera playback in real time looks like

Michael Hyun · July 8th, 2003, 11:15 PM

i was actually thinking more along the lines of HD DVD when it comes out. (isn't DVHS a jvc product? correct me if i'm wrong)

anyways, an interesting test to do would be to downconvert the 720 30p and burn a dvd. would the flickering evident on high shutter speed pans and motion be attenuated?

Michael Hyun · July 8th, 2003, 11:17 PM

joe, you beat me to it ^^

can you tell us what it might look like if you are anywhere close to burning a test dvd yet?

Joe Russ · July 8th, 2003, 11:20 PM

certainly will....and i plan on posting some samples as soon as i get my other light kit set up

Chaim Bianco · July 9th, 2003, 02:28 PM

steve mullen writes:

>Proof, they say, is to look at each frame one by one. And, they are >right!!! Each frame is perfectly clear.

well, if you step through each frames one at a time on a computer monitor and you dont see it, then it isnt there.

it sounds like either the camera's up-and-downconverter or the monitor itself are handling the 30p frames in an evil manner. like maybe interpolating to 60i like this:

frame1, frame1/frame2, frame2, frame2/frame3, frame3

are you familiar with what NTSC looks like when the field-order inverted? or when you play 60i video backwards. does it remind you anything like that?

>There is one other possibility. It's not in our heads. Possibly
>the camcorder's upconverter is blending 2 frames to "smooth" the
>rate >conversion. (It's the same upconverted to 1080i or down
>to 480p or 480i.)

if you want to convert 720p to SD, the best thing would to be

capture mpeg2-ts
demux to mpeg2
convert mpeg2 to lossless yuv 720p
drop it onto NLE timeline
render to dv-ntsc

am i wrong in assuming that everyone here uses some form of NLE prog (premiere, fcp, vegas, etc?)

btw -- if you post a 6 second clip in mpeg2-ts or mpeg2, i'd be happy to do the conversion tonite as a test.

cbianco

Heath McKnight · July 9th, 2003, 02:41 PM

How do you demux mpeg2-ts to mpeg 2? This is all foreign to me.

heath

Chaim Bianco · July 9th, 2003, 02:41 PM

joe russ wrote:

> 1/60th is fine (for normal motion) and converts very well to
> 24p >(important to me) with no motion stutter.

how are you converting 30p to 24p -- by dropping frames ?

cbianco

Chaim Bianco · July 9th, 2003, 02:46 PM

heath wrote:

> How do you demux mpeg2-ts to mpeg 2? This is all foreign to me.

if you are using a pc, you can use " xmuxer ":

http://www.moonlight.co.il/download/

cbianco

Heath McKnight · July 9th, 2003, 02:58 PM

<<<-- Originally posted by Chaim Bianco : heath wrote:

> How do you demux mpeg2-ts to mpeg 2? This is all foreign to me.

if you are using a pc, you can use " xmuxer ":

http://www.moonlight.co.il/download/

cbianco -->>>

What about FPC/Apple?

heath

Joe Russ · July 9th, 2003, 03:46 PM

<<<-- Originally posted by Chaim Bianco :

how are you converting 30p to 24p -- by dropping frames ?

cbianco -->>>

no dropping frames per say, im doing the conversion in after effects using a revision plugin called twixtor, it works quite well with all the settings right.

Jay Nemeth · July 10th, 2003, 02:47 AM

Greetings to the forum,

I have been shooting tests with this camera for about 10 days, and I also noted the double image. Although there are many frustrating aspects of this camera, the double image is not a malfunction but a phenomenon known as eye tracking. It is something that cinematographers have always known about and had to deal with.

The JVC camera truly runs at 720/30p, but it always outputs 60 images per second. Even in the "no conversion" output setting, the 720/30p is output at 720/60p, each frame repeated twice. I have seen this same effect whether outputting 1080/60i to an HDTV monitor or outputting 720/60p to an 8' wide CRT projector.

It is the same effect experienced viewing a fast pan in the movie theater where the 2 bladed shutter flashes each of the 24 frames twice, for a 48fps projection rate.

Please read here for more info: http://www.poynton.com/papers/Motion_portrayal/

The author speaks of motion picture, tube video and ccd capture devices as well as film projection, plasma and DMD displays and HDTV. Go to figure 19 for an explanation of this odd effect.

Even though this is a CCD imager recording HDTV, the double image we are seeing is analogous to the 24fps film being displayed at 48fps, each frame flashed twice. And, yes, the 1/30th of a second shutter speed does help mask it.

While the JVC camera does not record interlaced as some have suggested, it's interesting to note that the Sony F900 in 24P, actually records in a mode called "field sequential" or 24Psf. Each progressive frame is recorded as an odd and even field. When you plug the analog output of the camera into an HD monitor that displays scan rate, it will read 1080/48i. Of course there are no motion artifacts between these two fields since they comprise a single progressive frame.

Jay

July 8th, 2003, 11:05 PM	#19
Steve Mullen HDV Cinema Join Date: Feb 2003 Location: Las Vegas Posts: 4,007	<<<-- Originally posted by Michael Hyun : if this is merely a camcorder playback issue, then theoretically the playback should be fine when other HD playback devices are produced. -->>> The problem is that both the DVHS and HD10 playback to video looking this way. That's how folks will see your work -- not on computer screens. Often very big screens. The displacement of the 2 images is 6-inches! We really need someone who also owns a DVX100 to shoot some 30p of moving cars and people. Is this a visual phenomena of all 30p? Or, is it it a function of a funky JVC rate-converter? __________________ Switcher's Quick Guide to the Avid Media Composer >>> http://home.mindspring.com/~d-v-c

July 9th, 2003, 02:41 PM	#25
Heath McKnight MPS Digital Studios Join Date: Apr 2003 Location: Palm Beach County, Florida Posts: 8,531	How do you demux mpeg2-ts to mpeg 2? This is all foreign to me. heath __________________ My Final Cut Pro X blog

July 9th, 2003, 02:58 PM	#28
Heath McKnight MPS Digital Studios Join Date: Apr 2003 Location: Palm Beach County, Florida Posts: 8,531	<<<-- Originally posted by Chaim Bianco : heath wrote: > How do you demux mpeg2-ts to mpeg 2? This is all foreign to me. if you are using a pc, you can use " xmuxer ": http://www.moonlight.co.il/download/ cbianco -->>> What about FPC/Apple? heath __________________ My Final Cut Pro X blog

July 8th, 2003, 10:53 PM	#16
Joe Russ Regular Crew Join Date: Jul 2003 Location: New York, NY Posts: 99	it seems like a playback issue because i dont have an hd screen and have been watching it on the computer (no upconverting or downconverting) and i dont see any of this double image/ghost image stuff, other then the obvious blurriness from 1/30th shutter speed

July 8th, 2003, 10:58 PM	#17
Michael Hyun Regular Crew Join Date: Jul 2003 Location: Detroit Posts: 46	this is an interesting development. this may mean that the jvc is actually more flexible than i originally thought. thanks joe for sharing that with us. i haven't captured any of my footage yet.... this may actually be the best news i've heard yet ^^

July 8th, 2003, 10:58 PM	#18
David Newman CTO, CineForm Inc. Join Date: Jul 2003 Location: Cardiff-by-the-Sea, California Posts: 8,095	Basically there isn't a capture problem with the camera -- it shoots true 30p. I don't play images directly off the camera (I don't know what that looks like), but the data that comes across firewire is exactly as it should be.

July 8th, 2003, 11:14 PM	#20
Joe Russ Regular Crew Join Date: Jul 2003 Location: New York, NY Posts: 99	i think its the output from the camera itself. and actually, my stuff will all be down converter to anamorphic dvd resolution and displayed at 24p, so, it doesnt matter what the camera playback in real time looks like

July 8th, 2003, 11:15 PM	#21
Michael Hyun Regular Crew Join Date: Jul 2003 Location: Detroit Posts: 46	i was actually thinking more along the lines of HD DVD when it comes out. (isn't DVHS a jvc product? correct me if i'm wrong) anyways, an interesting test to do would be to downconvert the 720 30p and burn a dvd. would the flickering evident on high shutter speed pans and motion be attenuated?

July 8th, 2003, 11:17 PM	#22
Michael Hyun Regular Crew Join Date: Jul 2003 Location: Detroit Posts: 46	joe, you beat me to it ^^ can you tell us what it might look like if you are anywhere close to burning a test dvd yet?

July 8th, 2003, 11:20 PM	#23
Joe Russ Regular Crew Join Date: Jul 2003 Location: New York, NY Posts: 99	certainly will....and i plan on posting some samples as soon as i get my other light kit set up

July 9th, 2003, 02:28 PM	#24
Chaim Bianco Regular Crew Join Date: Jul 2003 Location: Philadelphia , PA Posts: 39	steve mullen writes: >Proof, they say, is to look at each frame one by one. And, they are >right!!! Each frame is perfectly clear. well, if you step through each frames one at a time on a computer monitor and you dont see it, then it isnt there. it sounds like either the camera's up-and-downconverter or the monitor itself are handling the 30p frames in an evil manner. like maybe interpolating to 60i like this: frame1, frame1/frame2, frame2, frame2/frame3, frame3 are you familiar with what NTSC looks like when the field-order inverted? or when you play 60i video backwards. does it remind you anything like that? >There is one other possibility. It's not in our heads. Possibly >the camcorder's upconverter is blending 2 frames to "smooth" the >rate >conversion. (It's the same upconverted to 1080i or down >to 480p or 480i.) if you want to convert 720p to SD, the best thing would to be capture mpeg2-ts demux to mpeg2 convert mpeg2 to lossless yuv 720p drop it onto NLE timeline render to dv-ntsc am i wrong in assuming that everyone here uses some form of NLE prog (premiere, fcp, vegas, etc?) btw -- if you post a 6 second clip in mpeg2-ts or mpeg2, i'd be happy to do the conversion tonite as a test. cbianco

July 9th, 2003, 02:46 PM	#27
Chaim Bianco Regular Crew Join Date: Jul 2003 Location: Philadelphia , PA Posts: 39	heath wrote: > How do you demux mpeg2-ts to mpeg 2? This is all foreign to me. if you are using a pc, you can use " xmuxer ": http://www.moonlight.co.il/download/ cbianco

July 9th, 2003, 03:46 PM	#29
Joe Russ Regular Crew Join Date: Jul 2003 Location: New York, NY Posts: 99	<<<-- Originally posted by Chaim Bianco : how are you converting 30p to 24p -- by dropping frames ? cbianco -->>> no dropping frames per say, im doing the conversion in after effects using a revision plugin called twixtor, it works quite well with all the settings right.

July 10th, 2003, 02:47 AM	#30
Jay Nemeth Regular Crew Join Date: Jul 2003 Location: Las Vegas, NV Posts: 64	Greetings to the forum, I have been shooting tests with this camera for about 10 days, and I also noted the double image. Although there are many frustrating aspects of this camera, the double image is not a malfunction but a phenomenon known as eye tracking. It is something that cinematographers have always known about and had to deal with. The JVC camera truly runs at 720/30p, but it always outputs 60 images per second. Even in the "no conversion" output setting, the 720/30p is output at 720/60p, each frame repeated twice. I have seen this same effect whether outputting 1080/60i to an HDTV monitor or outputting 720/60p to an 8' wide CRT projector. It is the same effect experienced viewing a fast pan in the movie theater where the 2 bladed shutter flashes each of the 24 frames twice, for a 48fps projection rate. Please read here for more info: http://www.poynton.com/papers/Motion_portrayal/ The author speaks of motion picture, tube video and ccd capture devices as well as film projection, plasma and DMD displays and HDTV. Go to figure 19 for an explanation of this odd effect. Even though this is a CCD imager recording HDTV, the double image we are seeing is analogous to the 24fps film being displayed at 48fps, each frame flashed twice. And, yes, the 1/30th of a second shutter speed does help mask it. While the JVC camera does not record interlaced as some have suggested, it's interesting to note that the Sony F900 in 24P, actually records in a mode called "field sequential" or 24Psf. Each progressive frame is recorded as an odd and even field. When you plug the analog output of the camera into an HD monitor that displays scan rate, it will read 1080/48i. Of course there are no motion artifacts between these two fields since they comprise a single progressive frame. Jay