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Old September 24th, 2010, 06:48 PM   #1
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Survey - Is YOUR GY HM-100 defective. (simple test)

First off I'm very sorry to start a "new" thread on this. However, I feel this issue is so important that it's something we ALL need to check out in our cameras.

Does YOUR camera capture "interlaced fields" in HQ 1080i 30p mode?

It's VERY possible that it does and you might not even know it! Why? Because your cam MUST be set manual at exactly a 1/30th shutter speed.

Try this simple test on your cam now;

1.) Switch to 1080 HQ 30P mode. This is the ONLY mode you will see it in.
2.) Go to full manual and record
3.) Hit the shutter button and drop it to EXACTLY 1/30th speed.
4.) Move camera slightly to generate motion.
5.) While on same recording, bump up shutter speed to 1/60th speed
6.) Move camera slightly to generate motion.

That's it! Throw your new clip into your editor. Make sure your project settings match 1080P 29.97 PROGRESSIVE. (screen on camera is too small to evaluate)

DO YOU SEE INTERLACING FIELDS ON THE 30 SHUTTER SCENE AND CLEAN PROGRESSIVE ON 60 SHUTTER PARTS? (try freezing clip or go slo-mo)

I'm betting many JVC GY-HM100's out there ARE doing the same thing at that shutter speed. I was told by JVC that all sensor images are natively read progressive and sent to the DSP to get processed. If you are in an interlaced mode, the DSP will split it into fields and send it to the encoder. All functions well with any other mode/speed combination but this combo is where the "glitch" happens.

Here are some simple screen shots. (Not edited in any way and are from the same clip literally seconds apart.)

30P 30 shutter;
http://dl.dropbox.com/u/4564537/30P%...%20shutter.jpg

30P 60 shutter;
http://dl.dropbox.com/u/4564537/30P%...%20shutter.jpg

It's very important to remember that these two screen caps are from the SAME "progressive" video clip. The ONLY change is the shutter speed!


Please try this simple test with yours and reply to the thread if you can. This is a problem that JVC has acknowledged and reportedly fixed in the "early" release models. Mine is only 3 months old and I purchased from BandH. Also has the latest "class 10 SD card" firmware.

I love my GY HM-100 and I think JVC Pro is a good organization. I have already spoken to two JVC support people and they are asking for me to ship my camera to them. My only goal in this thread is to see how widespread the issue is. It's not to "slam" JVC.

CT

Last important note: 1080 24P recording does NOT show this problem at any shutter speed. You must be in the exact combo of 1080 HQ 30P with 1/30 shutter.

P.S. For those needing to see the raw .mp4 video that these 2 pix came from, you can download it here. It's about 250 megs.

http://dl.dropbox.com/u/4564537/884_0158_01.MP4

Last edited by Cliff Totten; September 25th, 2010 at 08:28 AM.
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Old September 26th, 2010, 08:18 PM   #2
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Yes, me too.

I just tested tested using your conditions and was able to reproduce it.
Pretty much always use 1/60th so I never saw it before.
Guess I'll be sending mine in too.
http://dl.dropbox.com/u/2246838/60th%201080%2030p.png
http://dl.dropbox.com/u/2246838/30th%201080%2030p.png
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Old September 27th, 2010, 12:09 AM   #3
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Me too

I get the interlacing when shooting 1080 30p with 1/30 shutter. It is fine with 1/60

I have the upgraded Firmware also.
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Old September 27th, 2010, 08:36 AM   #4
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I KNEW it!!

JVC has been very polite about this so far. However, I get the slight feeling that they don't beleive me yet. They saw my footage and are now asking for my camera, so I guess I'll send it in.

Guys,..It is my humble belief that ALL our cameras have this problem.

Keep testing and PLEASE post your results!

Thanks, you guys ROCK!

CT

PS,..this problem is particularly bad because these interlacing fields CAN'T be removed from an already progressive frame. It's literally "burned" into the image that way.
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Old September 28th, 2010, 07:57 PM   #5
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Has anybody tested their GY-HM100, found the problem AND simply does not care about it?

Just wondering.

CT
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Old September 28th, 2010, 10:22 PM   #6
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Well, I have a new(ish) HM100 and I definitely care (and have been watching this thread) -- it's just that I won't be in any position to test it until next week at the earliest...
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Old September 29th, 2010, 09:50 AM   #7
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It's like the same problem with the RED, with p25 you must shot your footage with 1/50 to get a good picture quality.
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Old September 30th, 2010, 07:00 AM   #8
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anyone know if this is the same with the PAL settings?
if so, would it be, 25p at 50 shutter is fine,
but, 25p at 25 shutter will show interlacing, yeah?
Forgive my newbness, but is it only the much talked about loss of quality of having to interpolate fields that makes this a problem?
Only because, when I convert to Neoscene and make interlaced footage into progressive, I just cant see the difference on a 50" plasma between the original and the new progressive file.
What am I missing?
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Old September 30th, 2010, 07:56 AM   #9
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Honestly not sure about PAL and it would be unfair to JVC for me to guess.

It's important to understand what is happening. The camera is placing interlaced fields or something very similar to it and "burning" them into a "solid" progressive frame codec. (another explanation is that the camera is simply reading out the sensor in some kind of a "strange" scan order.)

The problem happens on NTSC when progressive the frame rate (High Quality 30p) and the manual shutter speed (1/30th of a second) meet together. Check your your PAL 25p and set your shutter for 1/25th.

Folks, this artifact CANNOT be removed. You cant "de-interlace" a frame that is NOT interlaced. These captured "field lines" are stuck in your image forever. (until you bump up the shutter to 60 or higher, than your video looks great)

MY GY HM-100 is now packed up and is going back to JVC today.

Test it and then fix it while you have a chance folks,

CT
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Old September 30th, 2010, 12:13 PM   #10
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Solved

Cliff - see my post: http://www.dvinfo.net/forum/jvc-gy-h...ml#post1574314
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Old October 1st, 2010, 12:57 AM   #11
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hey, well I have bad news for all us PAL people,
just checked,
1080 25p 25 shutter = Interlaced frames. :(((((
1080 25p 50 shutter = all is good.
I guess im ringing JVC....
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Old October 1st, 2010, 02:20 AM   #12
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@all
i will test it this weekend, is the problem in 720p50 too?
I´m Recording in Pal.
greetings
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Old October 1st, 2010, 01:59 PM   #13
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I thought this was pretty much a universal problem with native 60i cameras. I have to use double the frame rate to overcome the interlacing with my Vixia HF-11.
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Old October 1st, 2010, 04:45 PM   #14
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I think there might be some misunderstanding as to what is happening. Lemme try to explain it differently.

This is essentially a "shutter" or "sensor readout" defect. The problem literally puts a "comb" effect into your image. If you were shooting in 60i this would be perfectly normal and natural. You could simply deinterlace each 1/60 field into one progressive (1/30 of a second frame rate) image if you want to.

However, this problem will place two visible "upper and lower fields" TOGETHER into a PROGRESSIVE frame that is 1/30th of a second. (it's a NASTY artifact when there is motion)

What "should" be happening is that you should see ONE, SOLID progressive image at 1/30th of a second into a codec running at 1/30 frame rate. Simple, right?

This defect literally destroys the quality of the 30P frame. It's is ruined forever and NOTHING can remove that artifact. Remember, you cant "deinterlace" an image that is NOT interlaced.

Again. I know I sound like a broken record on this but I REALLY hope that all GY HM-100 owners take this seriously. If you shoot in manual, you could very well have a camera that will permanently "F-up" your footage!!!

If you are reading this and care about your video quality, check your camera now. (I wont say it anymore)

I feel bad for JVC but they need to issue some kind of public warning or recall notice on this. I'm glad I spotted the issue with test footage then to have found it with "real" footage. I would have DIED if I shot this for customer paying event. (thank God)

CT

Last edited by Cliff Totten; October 1st, 2010 at 05:34 PM.
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Old October 1st, 2010, 05:26 PM   #15
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Thanks for posting all of this, Cliff! I really appreciate it. I'm going to check my camera tomorrow.
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