Author Topic: Uh oh, you're interlaced, Dave!  (Read 20111 times)

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Offline tesla500

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Uh oh, you're interlaced, Dave!
« on: July 09, 2011, 12:51:41 pm »
Hey Dave, I notice you've got a new camera (or you're processing your videos differently lately), because the video has interlacing artifacts. It's subtle, but highly annoying, at least to me. You'll need to either set your camera to progressive scan mode (1080p/720p as opposed to 1080i) (preferable), or de-interlace the output of your video editor (less preferable, time consuming, quality loss).

Hopefully you didn't buy a camera that doesn't support progressive scan!  I wish interlaced video would die already, the only display technology that can show it properly is CRT, all other technologies are native progressive scan.

David
 

Offline Zad

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Re: Uh oh, you're interlaced, Dave!
« Reply #1 on: July 09, 2011, 02:03:28 pm »
Yep I noticed this too. It should be possible to de-interlace it when processing it to get rid of the interlace lines.

I also noticed that if you tab away from the window, the video slowly gets out of synch with the audio when you tab back in. I guess this is a codec issue, as it has done it before in the past. No biggie though.

Online EEVblog

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Re: Uh oh, you're interlaced, Dave!
« Reply #2 on: July 09, 2011, 02:14:56 pm »
Yes, I just realised this yesterday.
It really shows up when you chose 1080P on youtube, and yes it is horrible. It is called "combing" and looks like this:


Yes, I shot the last two blogs in 1440x1080 in 50i mode, not knowing any better.
Unfortunately the Canon HF G10 does not support 50P mode, only 25P. So I guess I'll have to shoot 25P.
I didn't think 50P mode was absolutely essential when buying the camera.
I haven't tried anything in software yet. I don't see an obvious "deinterlace" option in VideoStudio.

Are their any pros here who know the best option?
i.e. Am I better of:
1) shooting in 25P, outputting in 25P, and living with the motion blur (which I find fine actually, it's the combing caused by interlacing that is horrible)
2) shooting in 50i, and rendering in 25P or 50P somehow?
3) shooting in 25P, and somehow outputting in 50P?

It's confusing, because everywhere I read, everyone seem to say it's better to use 50i because it captures moving images much better than 25P, but as you can see the results in my case are just horrid. Perhaps I'm just not rendering the video correctly?
I need to run some test on this.

Here is test footage I did yesterday comparing 50i and 25P





You have to select 1080P in Youtube to see it.

Thanks.
Dave.
« Last Edit: July 09, 2011, 02:22:41 pm by EEVblog »
 

Offline vtl

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Re: Uh oh, you're interlaced, Dave!
« Reply #3 on: July 09, 2011, 02:36:49 pm »
Isn't the industry film standard 1080p/24fps? Theres really no need for interlaced because you're not filming fast movment much. Even for fast movment I'd still stick to progressive because only CRTs do it properly.
 

Offline Lightages

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Re: Uh oh, you're interlaced, Dave!
« Reply #4 on: July 09, 2011, 03:30:09 pm »
IMHO, as humble as I can be, shoot 25P and render in 25P. DO NOT use interlaced. For video blogging and using your normal lighting (50Hz) do not use 24P or you will have flickering.

If you want the "film look" use 1/50 second for shutter speed while shooting 25P. If you want less motion blur use 1/100 or faster shutter speed. The problem with 25P and too fast a shutter speed is that motion will look strobed. Personally I would use either 1/50 or 1/100 shutter speed for your use.
 

Online EEVblog

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Re: Uh oh, you're interlaced, Dave!
« Reply #5 on: July 09, 2011, 03:43:38 pm »
IMHO, as humble as I can be, shoot 25P and render in 25P. DO NOT use interlaced. For video blogging and using your normal lighting (50Hz) do not use 24P or you will have flickering.

My camera is PAL and not capable of 24P. 25P only, which is actually "FP25" saved as 50i.

Dave.
 

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Re: Uh oh, you're interlaced, Dave!
« Reply #6 on: July 09, 2011, 03:46:29 pm »
Isn't the industry film standard 1080p/24fps? Theres really no need for interlaced because you're not filming fast movment much. Even for fast movment I'd still stick to progressive because only CRTs do it properly.

See, that's the stupid thing. You are supposed to use interlaced for "fast motion", but the results are terrible. The 50i straight out of my camera is horrible on anything that moves. And this is a latest generation top of the line Canon HF G10.

I have not been able to find anyone who can give me an answer on this on various forums.

Dave.
 

Offline Lightages

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Re: Uh oh, you're interlaced, Dave!
« Reply #7 on: July 09, 2011, 03:58:04 pm »
IMHO, as humble as I can be, shoot 25P and render in 25P. DO NOT use interlaced. For video blogging and using your normal lighting (50Hz) do not use 24P or you will have flickering.

My camera is PAL and not capable of 24P. 25P only, which is actually "FP25" saved as 50i.

Dave.

Good! Just use 25P and forget about it. Adjust your shutter to your liking between blurred motion and strobed motion effect. Film "standard" is usually twice the shutter speed of the frames per second. Or in more archaic terms, 180 degrees of shutter. This is when shutters used to be two rotating discs with half the disc missing and you could adjust the overlap of the two discs to achieve different degrees of open duration.
 

Offline Lightages

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Re: Uh oh, you're interlaced, Dave!
« Reply #8 on: July 09, 2011, 04:06:02 pm »

See, that's the stupid thing. You are supposed to use interlaced for "fast motion", but the results are terrible. The 50i straight out of my camera is horrible on anything that moves. And this is a latest generation top of the line Canon HF G10.

I have not been able to find anyone who can give me an answer on this on various forums.

Dave.

Nobody (sane) uses interlaced professionally. It is all shot in progressive mode. The advice to shoot interlaced by Canon or in the  manuals is just to justify its existence in the camera as a fallback to older display tech. Properly de-interlacing video basically is always a compromise. Interlacing should be avoided whenever you can unless your intended market is solely for interlaced display devices like old TVs.
 

Offline tesla500

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Re: Uh oh, you're interlaced, Dave!
« Reply #9 on: July 09, 2011, 04:16:58 pm »
Shooting and processing all in the same format is the way to go, 25p in this case. At the moment, more is pointless, because youtube only encodes their video up to 30fps. They will reduce the frame rate, probably by decimation (dropping every nth frame), of anything uploaded with a higher frame rate. However, I guarantee Google keeps all the originals, so if they allow higher frame rates later, videos uploaded as 50/60fps may be re-encoded by them.

The reason interlaced looks horrible is that your computer doesn't know how to display it properly. If you hooked your camera up to a TV or played the video using VLC Media Player with deinterlacing enabled,it would look much better. There's no easy to use solution for deinterlacing during encoding, when I was using an interlaced NTSC camera, I used Avisynth with the TomsMoComp deinterlacing plugin, encoding with VirtualDub. This was a whole extra step after editing, and was a big pain.

I would have suggested a camera such as a Panasonic TM700 (which I have), which is one of the very few that shoots 1080p60.
 

Offline jahonen

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Re: Uh oh, you're interlaced, Dave!
« Reply #10 on: July 09, 2011, 04:20:03 pm »
Isn't the industry film standard 1080p/24fps? Theres really no need for interlaced because you're not filming fast movment much. Even for fast movment I'd still stick to progressive because only CRTs do it properly.

See, that's the stupid thing. You are supposed to use interlaced for "fast motion", but the results are terrible. The 50i straight out of my camera is horrible on anything that moves. And this is a latest generation top of the line Canon HF G10.

I have not been able to find anyone who can give me an answer on this on various forums.

Dave.

I think that there is nothing wrong with the camera, but modern panel displays have trouble displaying an interlaced material properly, as they are inherently progressive. Deinterlacing is very heavy black magic to do acceptably. So, it is better to avoid that altogether and stick with the progressive mode anyway, so like others already said, just use 25p mode.
 
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Offline vtl

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Re: Uh oh, you're interlaced, Dave!
« Reply #11 on: July 09, 2011, 04:49:49 pm »
IMHO, as humble as I can be, shoot 25P and render in 25P. DO NOT use interlaced. For video blogging and using your normal lighting (50Hz) do not use 24P or you will have flickering.

Good cameras these days should have a filter for flickering. On my Nikon D3100 theres an option to select the filter to 50Hz or 60Hz. In video mode (1080p/24) theres no flicker at all sitting directly under fluorescent lighting.
 

Offline Lightages

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Re: Uh oh, you're interlaced, Dave!
« Reply #12 on: July 09, 2011, 04:52:36 pm »
Let me rephrase that. You can have problems with flickering.
 

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Re: Uh oh, you're interlaced, Dave!
« Reply #13 on: July 09, 2011, 05:46:45 pm »
IMHO, as humble as I can be, shoot 25P and render in 25P. DO NOT use interlaced. For video blogging and using your normal lighting (50Hz) do not use 24P or you will have flickering.
Good cameras these days should have a filter for flickering. On my Nikon D3100 theres an option to select the filter to 50Hz or 60Hz. In video mode (1080p/24) theres no flicker at all sitting directly under fluorescent lighting.

My old Sanyo Xacti had a flicker filter, and I think you could select 50/60
But the new Canon doesn't have any filter option.
I wonder if that means it would flicker if I shot footage in the US under 60Hz lights?

I don't understand why cameras are sold in PAL and NTSC version with 24p/25p and 50i/60i modes. Why can't this all just be in software?

Dave.
 

Offline Lightages

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Re: Uh oh, you're interlaced, Dave!
« Reply #14 on: July 09, 2011, 06:20:39 pm »

I don't understand why cameras are sold in PAL and NTSC version with 24p/25p and 50i/60i modes. Why can't this all just be in software?

Dave.

It is usually the opinion that the manufacturers do not want to eat into the sales of their higher end products. It should be easy of course but money makes these decisions......

Flicker filters don't always work BTW.
 

Offline Kiriakos-GR

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Re: Uh oh, you're interlaced, Dave!
« Reply #15 on: July 09, 2011, 07:37:18 pm »

My old Sanyo Xacti had a flicker filter, and I think you could select 50/60
But the new Canon doesn't have any filter option.
I wonder if that means it would flicker if I shot footage in the US under 60Hz lights?

The human eye can detect up to 18FPS as far I know , the 25 offers an maximum smoothness to the ones who can feel the difference, not every one does.

I don't understand why cameras are sold in PAL and NTSC version with 24p/25p and 50i/60i modes. Why can't this all just be in software?

Dave.
PAL and NTSC = compatibility
30 FPS VS 60i modes =  richest color cast for the second.
The 60i demands even more bandwidth ( +20%) , and probably uses the CCD in a way like the digital still image cameras uses the RAW format.
In simple words, the CCD output, goes to separate electronics, that can handle such digitizing format.

I could think of a similar example with sound and bit rate,
like 44.1kHz  40kHz 88.2kHz 96kHz .
Even if 44.1kHz sounds good for the many , the theoretical maximum of sound quality it is served at the max with 96kHz sample rate.
This is why I will record my music at  96kHz  = Master copy , and then I will downgrade it by having in mind the specs of the play back device. 

About software editing, I found  that the Corel VideoStudio Pro X3 has the maximum compatibility with the 60i = 60 fields/S mode, at 1920X1080 full HD.

The Sanyo can not do full HD at 1920X1080 SHQ !! or any other mode that is based in Frames per second.   
 

Online EEVblog

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Re: Uh oh, you're interlaced, Dave!
« Reply #16 on: July 09, 2011, 09:21:07 pm »
Shooting and processing all in the same format is the way to go, 25p in this case. At the moment, more is pointless, because youtube only encodes their video up to 30fps. They will reduce the frame rate, probably by decimation (dropping every nth frame), of anything uploaded with a higher frame rate. However, I guarantee Google keeps all the originals, so if they allow higher frame rates later, videos uploaded as 50/60fps may be re-encoded by them.

The reason interlaced looks horrible is that your computer doesn't know how to display it properly. If you hooked your camera up to a TV or played the video using VLC Media Player with deinterlacing enabled,it would look much better. There's no easy to use solution for deinterlacing during encoding, when I was using an interlaced NTSC camera, I used Avisynth with the TomsMoComp deinterlacing plugin, encoding with VirtualDub. This was a whole extra step after editing, and was a big pain.

I would have suggested a camera such as a Panasonic TM700 (which I have), which is one of the very few that shoots 1080p60.

1080p60/50 doubles the video rate though doesn't it? So I probably wouldn't use 1080p50 even if I had it.

Dave.
 

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Re: Uh oh, you're interlaced, Dave!
« Reply #17 on: July 09, 2011, 09:36:04 pm »
The reason interlaced looks horrible is that your computer doesn't know how to display it properly. If you hooked your camera up to a TV or played the video using VLC Media Player with deinterlacing enabled,it would look much better.

Ah, VLC does indeed have a deinterlace option, with no less than 8 different algorithms to chose from.
Yes, it looks much better now, just the usual motion blur.
Doesn't help the uploaded Youtube video of course.

The raw PF25 video looks better than the "deinterlaced" 50i video though.

I just noticed my Handbrake program has a "decomb" filter which will likely work and get me decent video.
But I don't see the point, might as well shoot in 25P to begin with.

And I guess that raises the question of what's the point of 50i mode?
Is there any benefit over 25P?
Because if I'm understanding this right (for the same raw bitrate, say 12Mbps that I use):
- 25P gives 25 full frames per second non-interlaced (obviously)
- 50i gives 50 interlaced "fields" per second, but still 25 full frames per second. But that means fast moving stuff gets this "combing" problem.

So what's the advantage of 50i? And why does every man and his dog seems to say it's better to use 50i for fast action stuff?

Dave.
 

Offline Kiriakos-GR

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Re: Uh oh, you're interlaced, Dave!
« Reply #18 on: July 09, 2011, 09:43:54 pm »
Well I like to believe that the interlaced thingy had to do mostly with anything is related to frames.
The Full HD uses fields and its another technology , totally compatible with every Full HD screen. 

The computer monitors that can support the Full HD resolution, they do just the half work.
The other half is made by the hardware or software decoder in our computers,
and so the results can vary by allot.

Youtube uses their own video engine and compression,
and I do not have any idea of how it works.
And no one haves any control over their codec's.

In my personal PowerDvd player I have control over the De-interlacing !!

And so the most wise act, would be to send a email at the technical support of Youtube.
And find out what works for them best.   
   
 

Online EEVblog

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Re: Uh oh, you're interlaced, Dave!
« Reply #19 on: July 09, 2011, 10:09:30 pm »
And so the most wise act, would be to send a email at the technical support of Youtube.
And find out what works for them best.   

It is clear from the test footage I uploaded, Youtube cannot display interlaced video in HD without the "combing" effect.
So I have to feed Youtube progressive video one way or another.

Dave.
 

Offline FreeThinker

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Re: Uh oh, you're interlaced, Dave!
« Reply #20 on: July 09, 2011, 10:58:21 pm »
Erm! this may seem like a silly question but why not just turn off the 1080 HD mode in youtube? Job done.
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Offline sonic

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Re: Uh oh, you're interlaced, Dave!
« Reply #21 on: July 09, 2011, 11:04:36 pm »
So what's the advantage of 50i? And why does every man and his dog seems to say it's better to use 50i for fast action stuff?

50i is actually quite efficient in transporting fluid motion: It keeps the non-moving background at full 1080 resolution and encodes the fast-moving subject at half the resolution (540 lines). Since the human eye can't resolve motion and resolution at the same time, interlacing leans to our visual perception system.
The only problem is that something has to adapt interlaced content to the progressive display devices in use (LCD). Normal video player software uses the graphics card hardware to deinterlace video with quite a good quality today. It's just this Flash based YouTube video player mess that doesn't get it at all. They just now managed to use the graphics card to decode the video without burning all CPU resources.
By the way, there is a discussion going on with german HDTV: all the public networks decided to broadcast in 720p50, but one is thinking about switching to 1080i50 because foreign source material is often mastered interlaced anyway.
Interlacing will only go away if the immense bandwidth increase of 1080p50 won't matter anymore.
« Last Edit: July 10, 2011, 05:54:34 am by sonic »
 

Offline ivan747

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Re: Uh oh, you're interlaced, Dave!
« Reply #22 on: July 10, 2011, 12:31:50 am »
Erm! this may seem like a silly question but why not just turn off the 1080 HD mode in youtube? Job done.

I watch 720"p" and it removes most of the interlacing.
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Offline Mechatrommer

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Re: Uh oh, you're interlaced, Dave!
« Reply #23 on: July 10, 2011, 01:34:31 am »
some software can decode the interlaced movie (source) into progressive mode (output). it seems video format industry got mixed up, pal/ntsc now can be set for either 50 or 60Hz?
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline tesla500

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Re: Uh oh, you're interlaced, Dave!
« Reply #24 on: July 10, 2011, 02:33:18 am »
The human eye can detect up to 18FPS as far I know , the 25 offers an maximum smoothness to the ones who can feel the difference, not every one does.

I'm not sure about the sensitivity of the human eye, but I can detect the difference between 25/30 and 50/60fps very easily. There is a significant difference in smoothness. Also, if your display strobes (displays the image as pulses of light, as in a CRT or plasma display), and the video frame rate matches the display strobe rate, you get a "perfect smooth" effect, it looks as smooth as if your frame rate was 1/shutter speed.

I don't understand why cameras are sold in PAL and NTSC version with 24p/25p and 50i/60i modes. Why can't this all just be in software?

I'm sure it's just a software difference, but they seem to not want to upgrade everyone to 30/60, even though they have the chance with HDTVs.

So what's the advantage of 50i? And why does every man and his dog seems to say it's better to use 50i for fast action stuff?

50 image samples per second is better for motion than 25, plain and simple. 50p would be even better because you have more image data.

50i is actually quite efficient in transporting fluid motion: It keeps the non-moving background at full 1080 resolution and encodes the fast-moving subject at half the resolution (540 lines). Since the human eye can't resolve motion and resolution at the same time, interlacing leans to our visual perception system.

That's true, or at least was back in the days of analog when you couldn't do digital compression. It was an ingenious analog compression system that halved the data rate. However, with modern codecs, I think it would it be better to simply send 50/60p, using the same bitrate as 50/60i. The codec does the same thing, loosing detail during motion, and having full detail when a static image is displayed. The codec can do a better job though, with features such as motion compensation (dragging pixels around at full resolution), while interlacing looses half your vertical resolution at the slightest motion.

1080p60/50 doubles the video rate though doesn't it? So I probably wouldn't use 1080p50 even if I had it.

Yes, the data rate is quite high, it runs at 28Mbps. But storage is cheap! The bigger problem was that my 2 year old computer wasn't fast enough to play the video from it, I had to get a new computer to play and edit the video.

David
 


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