HV20 - a real progressive sensor or not?
 

My friend shooted in 25p mode with the HV20 in Seychelles.
The video isnt smooth, very eye strain for me. I think its because lack of ND filter, and the camera use very short shutter speed.

But my real problem is, that not every frame looks progressive! Yes! Not every. I import the native m2t file into Edius4 1440x1080 25p project, and set the file properties to progressive (because edius think its a 50i file). When i go from frame to frame i found this 2 interesting frame!
(indicated with green arrow)
http://www.relaxvideo.hu/hv20a.jpg
http://www.relaxvideo.hu/hv20b.jpg

this looks like a deinterlaced frame from an interlaced video, doesn't?
but the next few frame is ok (one tree, one rock, without shadow)
So periodically hv20 insert a deinterlaced frame or the whole cmos sensor isnt a real progressive one?

This is only for PAL model, i dont know the NTSC version, but like to hear about it.

Hi Prech. From what I see, that could be motion blur rather than deinterlaced video.

Richard

I think I agree w/Richard. That doesn't look like interlace artifacting.


-A

yes, it does, every other frame looks normal.
One blurred tree trunk, not 2 shadowed..

I work in video area for many years now, and from my experience, this looks like a deinterlaced frame.

If its just motion blur, then why do i see two trunk from one tree?
I upload the previous and the next few frames, you will see the difference:
http://www.relaxvideo.hu/hv20

I have seen this ghosting as well on faster moving shots at 24p (and you are in more authorative position as you use 25p, without a need for pulldown removal). It looks like resampling to me.

Resampling may result blurry image, but why ghostly?
I know it has to be resampled from 1920x1080 to 1440x1080, but when you squeeze horizontaly the full progressive frame, why appear this edge ghost effect?
It seems to me, that hv20 can readout the sensor only in interlaced mode, but in 25p mode doesn't have to wait 1/50 sec for the next readout, like in normal 50i mode. Instead if it finish the upper rows, immediatly goes for the lower rows, and its take time because the rolling shutter effect.
What else can explain this?

Hi Prech. I have an HV30 but to be honest I have not used it very much so far and have not played around with all the modes yet.

But from what I know, when you set the camera to Cine mode, it is possible that the camera will adjust the shutter speed automatically while you are shooting. So I am wondering if you are seeing motion blur in some frames but not in others because the camera has selected a slower shutter for those frames? Is it possible?

Richard

No, it is because it was a handheld shot. sometimes the pictures is steady (no motion blur), another time on fast moving, motion blur exist. This is normal.
What would be the reason to change the shutter speed for an existing landscape and light situation?
And even if camera change the shutter speed, that doesnt explain the two trunk. dont you think?

Look at the TV in the image...
 

This is a single frame from a clean 24P-deinterlace process, HDV. Obvious motion blur and a slight lean, and I'm going assume the shutter was 1/24 due to the low-light.

The bright areas of the image have a blur as the camera was in motion, but I'd think the TV's 'multiple exposures' are merely due to the fact it's scanning at 60i. The LCD monitors - also bright - blur as one would expect - smoothly.

It's a CMOS sensor, and I expect it to be true progressive. The HV20 is a year old now, and this topic has been throughly discussed here.

Hi Prech. I understand what you are saying about the shutter speed, but it is also possible that the lighting conditions are just on the threshhold of what would make the camera select a different shutter speed. I'm not saying this is likely, just mentioning the possibility.

The 2 trunks thing does look strange, but it doesn't look like a deinterlacing issue to me. Do you happen to know what the shutter speed was for this shot? Also, have you seen such an effect when the shutter speed was fixed?

Richard

Richard, unfortunatelly i wasnt in Seychelles yet.
My friend was there.
If the light condition change a little bit, i think the camera first try to adjust the iris, not the shutter speed. (on prof. TV camera, shutter speed is always 1/50).
but anyway, again my question: if there is a shutter speed change, why do is see on this frame two trunk?
What else when not a two different field -> one full frame conversion?

regards

Hi Prech. This is a clip taken with an HV30 in 25P progressive mode.

http://www.jaegersing.com/25P_Test.m2t

I opened it in Vegas and every frame looks progressive to me. The shutter speed is around 1/250s so there is little motion blur to confuse matters.

Maybe you can take a look at it using Edius and see if you get any strange frames?

Richard

Sorry I had to take down this clip because it exceeded my bandwidth allocation. Oops!

yes!
it looks a real progressive material
but with hv30

Yeah, I wasn't sure how useful it was to compare this way round. Maybe you could post a short section of your "double-image" m2t and let me take a look in Vegas?

Richard

The 24fps progressive images of your camera are stored within a 60fps interlaced envelope. To extract the original frames, you need to pass your footage through a process known as 3:2 pulldown.

Here's one way to do it:
http://eugenia.gnomefiles.org/2007/0...-24p-pulldown/

It was wrong of you to resize the image. By doing so, you ended up blending the interlaced frames. Also, the video will be really stuttery on playback. More stuttery than normal 24p.

It's either you leave the image at 60i and output it to a DVD which results in a perfect image on a real TV set or you go through the pulldown process discussed in the link supplied above, or some other method.