> Interlaced and motion blur <

[Dark Alpha]

Hey guys

I was wondering, what exactly causes the blur effect on full-motion-interlaced-videos when viewing on a standard interlaced CRT? I mean, on soaps, news, sports etc… what actually cause the motion blur during movement?

The reason I’m asking this is because in full-motion-video games (such as Call of Duty, Burnout, Timesplitters etc…) and few music videos, there was no motion blur what so ever.

That’s what confuses me cos how-come certain interlaced videos suffer from motion and others don’t.

>>> Please keep in mind that I’m talking about full motion (not film) and CRT (not FPDs) <<<





This is a standalone software , so you don’t need to install it. Once the download is complete, click on 25 > 75Hz. Please ignore all the writing and concentrate on the top and the bottom.

To show what I mean, let’s say the top image is 60i (59.94) and the bottom is 30i (29.97).



If you’re viewing this on a progressive CRT monitor, you can see that there is no visible motion blur on the top image.


That’s exactly what I saw when playing (full-motion) video games (rendered at 60fps) and viewed the music videos.


Could you please explain to me how is this possible on a interlaced SD-CRT?

[jagabo]

Cameras (both fild and video) take an exposure over a period of time. Anything that moves, or if the camera is moving, ends up blurred because it's image is spread out over the area in which it moved.

Comptuer games render frames as fixed points in time. They essentially have a zero exposure time. Or think of it as if everything was standing perfectly still during the exposure.

This has nothing to do with interlacing really.

For example, let's draw a picture in the sand. Smooth out the sand to get a nice blank canvas. Poke the point of a stick into the sand. Hold it perfectly still for one second then remove it. You have a nice "photo" of the point of the stick -- a little round hole in the sand. Now repeat this one second exposure, but this time move the stick to the side instead of holding it still. The point of the stick has now blurred into a line.

[theewizard]

not counting the actual blur on FILM

motion blur, or what SEEMS to be motion blur , on a crt is a function of phosphor glow, interlace TV ihas/is 2 feilds

the top field ( odd numbered lines ) is sent, the phosphor is still glowing when the bottom field (even numbered lines ) is displayed but the object moved so you have the glow from the first field first position and the glow from the second field second position this is the blur ,

NOTE: when interlaced video improperly captured or improperly resized, this 2nd field movement ,becomes the jaggies seen in captured mpeg video

[edDV]

For example. Take a picture (frame) of a moving object with your stationary digital camera. The moving object will be blurred. The slower the shutter speed, the more burred it will be.

Likewise follow a moving object with your camera. The background will be blurred due to motion over the exposure.



Interlace video takes a picture with odd lines followed by even lines 1/60 (1/50th second for PAL) later.

Progressive video takes a full picture every 1/29.97th or every 1/59.94th sec (1/25th or 1/50th sec. for PAL).

[Dark Alpha]

Cameras (both fild and video) take an exposure over a period of time. Anything that moves, or if the camera is moving, ends up blurred because it's image is spread out over the area in which it moved.

Comptuer games render frames as fixed points in time. They essentially have a zero exposure time. Or think of it as if everything was standing perfectly still during the exposure.

This has nothing to do with interlacing really.

I think I know what you mean

[jagabo]

Interlacing and motion blur are two separate subjects.

Yes, interlaced video from a video camera will contain two half pictures, taken at two different times, woven together, as depicted in your png file. But these two half-pictures may, or may not, be blurred due to motion (depending on how fast things were moving and the length of the exposure).

Video games may generate progressive or interlaced frames. Computer games will generate progressive frames. But in either case the images are almost never motion blurred. Motion blur is too compute intensive for games.

[lordsmurf]

fps is the cause.

[Dark Alpha]

so what you guys saying is, interlaced is not the cause of motion blur?

[TheFamilyMan]

As already described, motion blur is an "artifact" of photography, whether it be digitial or not, induced by the brisk motion of the subject/background being photographed. Major movies with CGI incorporate its effect because our minds tell us that it's more "realistic", since that is what a real object would look like if filmed. Games don't but could, for reasons aready mentioned (I'd imagine some DX12 with motion blur coming along someday when there are 6G cpus).

[jagabo]

so what you guys saying is, interlaced is not the cause of motion blur?

Right. Although some types of deinterlacing or improper treatment of interlaced material can lead to something that looks like motion blur.

[edDV]

so what you guys saying is, interlaced is not the cause of motion blur?

Be more clear about what you are asking.

There is motion blur which is a frame exposure issue. And then there is blurred motion resulting from poor deinterlacing. For example:

[Dark Alpha]

ya, I know de-interlacing, pixel response time, scaling and video enhancement (such as noise reduction, edge sharper, etc...) can cause motion blur so that’s why I concentrated solely on CRTs

PS: What's with the very high noise reduction on the image above?

[Dark Alpha]

What would happen if I ware to capture a video in progressive (60p)? Would there be motion blur?

[edDV]

"Motion blur" is being discussed differently in various fields.

Film: It is a parameter of exposure as discussed and is used creatively for various film effects. The same issues apply for 24p video but video lacks some of the better "chemical" effects.

High end 3D Graphics: It has been determined that lack of film-like natural motion blur is what causes rendered imagery to look sterile and artificial. They are hard at work to add motion blur for a more natural look.

Home Photography: The classic "say cheese" means "stop moving about so we can get a sharp picture".

Computer Games: A low end version of the 3D graphics discussion such as "smoke should not have sharp edges"

Low End deinterlacing: They argue about ways to mask field ghosting with various artificial blur tactics.

[edDV]

PS: What's with the very high noise reduction on the image above?

That was just a frame out of a 1080i MPeg2_TS stream. Blame CBS or Comcast for overprocessing. It may have been an instant replay.

[edDV]

What would happen if I ware to capture a video in progressive (60p)? Would there be motion blur?

You mean a bob? A bob interpolates a full frame @ 59.94fps from field data (including prior, current and/or subsequent fields). Bob works well for slow motion but falls apart in areas with moderate to high motion.

[Dark Alpha]

not de-interlacing, I mean actually capturing a video in 60fps (60p)

Over in the US, sports are broadcasted at 720p60 instead of 1080i60 because it eliminates motion blur???

[lordsmurf]

I can photograph a baseball as it leaves the hands of a pitcher, with a shutter speed of 1/2000th of a second, and it's still blurred slightly. There's no chance for video to not have blur on an object like this.

[Guiboche]

Motion blur is not entirely related to frame rate.

So, if you were to shot in real 60p, that framerate doesn't neccesarily mean there would be more or less motion blur.

It would be related to the shutter speed.

This is why the blur you're talking about is different on music videos, because they are usually shot with a faster shutter speed then what is usually used on film or even sports programs. The faster the shutter, the less blur (and less light), and vice versa.

[Dark Alpha]

I'm not talking about something that fast lol

Lets just say, two cameras are placed on a rotating table. It takes 5 seconds for the table to complete one round. One of the camera is interlaced (A) and the other is progressive (B). Both cameras are recording at full motion (60i and 60p). After recording for 1 minute, the videos from the cameras are transferred on to a PC.

The footage recorded from camera B was displayed on a progressive CRT and did not show any form of motion blur. However, the footage recorded from camera A was displayed on a interlaced CRT and had considerable amount of motion blur.

Why is that?

[edDV]

not de-interlacing, I mean actually capturing a video in 60fps (60p)

Over in the US, sports are broadcasted at 720p60 instead of 1080i60 because it eliminates motion blur???

Progressive video doesn't have time spaced fields but we have said interlace doesn't affect motion blur. Interlace video adds motion detail or smoothness at the tradeoff of some vertical resolution and flicker. 29.97fps 480i or 1080i will have 59.94 field per second motion detail.

Progressive video requires more bandwidth or bitrate to get similar frame rate and frame size. So while 1080i/29.97 can get motion at 59.94 field rate, it still causes difficulty for progressive display deinterlacers. At the same bitrate, 1280x720p can be run at full 59.94 frames per second for full motion detail and stop motion detail. Progressive displays look great since no deinterlacing is required.

720p has great advantage for high motion sports like football, hockey and soccer. It lacks the low motion detail of 1080i for sports like golf or baseball. 1080i/29.97 can still look good on an interlace display but tends to soften during camera or object motion and can have motion artifacts on progressive displays.

So, acquiring progressive video at 59.94 frames per second gives great motion detail but is unrelated to "motion blur" unless you are talking about deinterlace artifacts.

Progressive video can be sampled at 29.97 fps or 23.976 fps as well. The difference is more jerky motion not blur.

[Dark Alpha]

Motion blur is not entirely related to frame rate.

So, if you were to shot in real 60p, that framerate doesn't neccesarily mean there would be more or less motion blur.

It would be related to the shutter speed.

This is why the blur you're talking about is different on music videos, because they are usually shot with a faster shutter speed then what is usually used on film or even sports programs. The faster the shutter, the less blur (and less light), and vice versa.

oh, I suppose the same applies for interlaced?

[Guiboche]

Because you can't show camera A's interlaced footage on a progressive CRT monitor without bluring or bobing the fields during playback. Or there would be combing artifacting throughout the footage......

[Guiboche]

Motion blur is not entirely related to frame rate.

So, if you were to shot in real 60p, that framerate doesn't neccesarily mean there would be more or less motion blur.

It would be related to the shutter speed.

This is why the blur you're talking about is different on music videos, because they are usually shot with a faster shutter speed then what is usually used on film or even sports programs. The faster the shutter, the less blur (and less light), and vice versa.

oh, I suppose the same applies for interlaced?

Yes. Shutter governs blur and light for any format. Film or video.

[Dark Alpha]

720p has great advantage for high motion sports like football, hockey and soccer. It lacks the low motion detail of 1080i for sports like golf or baseball. 1080i/29.97 can still look good on an interlace display but tends to soften during camera or object motion and can have motion artifacts on progressive displays.

.

Bingo, thats what I'm trying to ask lol

Could you please tell me what causes that and why it doesn't effect video games

[Guiboche]

I'm not talking about something that fast lol

Lets just say, two cameras are placed on a rotating table. It takes 5 seconds for the table to complete one round. One of the camera is interlaced (A) and the other is progressive (B). Both cameras are recording at full motion (60i and 60p). After recording for 1 minute, the videos from the cameras are transferred on to a PC.

The footage recorded from camera B was displayed on a progressive CRT and did not show any form of motion blur. However, the footage recorded from camera A was displayed on a interlaced CRT and had considerable amount of motion blur.

Why is that?

Along with my answer above, and, as well, usually the fields are forcefully blended together. Depending on what you choose to view that footage with.

[Dark Alpha]

I'm not talking about something that fast lol

Lets just say, two cameras are placed on a rotating table. It takes 5 seconds for the table to complete one round. One of the camera is interlaced (A) and the other is progressive (B). Both cameras are recording at full motion (60i and 60p). After recording for 1 minute, the videos from the cameras are transferred on to a PC.

The footage recorded from camera B was displayed on a progressive CRT and did not show any form of motion blur. However, the footage recorded from camera A was displayed on a interlaced CRT and had considerable amount of motion blur.

Why is that?

Along with my answer above, and, as well, usually the fields are forcefully blended together. Depending on what you choose to view that footage with.

Footage from camera A was displayed on a interlaced CRT, so there no need for de-interlacing

[edDV]

I'm not talking about something that fast lol

Lets just say, two cameras are placed on a rotating table. It takes 5 seconds for the table to complete one round. One of the camera is interlaced (A) and the other is progressive (B). Both cameras are recording at full motion (60i and 60p). After recording for 1 minute, the videos from the cameras are transferred on to a PC.

The footage recorded from camera B was displayed on a progressive CRT and did not show any form of motion blur. However, the footage recorded from camera A was displayed on a interlaced CRT and had considerable amount of motion blur.

Why is that?

I think the problem you are seeing is caused by the computer.

If you spin the table at 480i/29.97 and connect directly to an interlace diaplay, there will be 59.94 unique time sliced fields per second. If you do the same with 480p/59.94, there will also be 59.94 time slices per second on an interlace display.

If the display was a PC progressive monitor with no deinterlace, you would see 59.94 fps time slices per second for 480p/59.94 but for 480i/29.97 you would see frames containing fields offset in time by 1/59.94th sec. like this. Since the PC requires fields to be paired into frames, you would see half the update rate 29.97fps with this double vision. This is the fault of the PC.



The motion in this frame was screen left to screen right. Note the time offset for the player and ball from field 1 to field 2.

[Guiboche]

Well you said "Transfered to a PC." Why would one need to transfer to a PC then to a monitor?

But, if anything, what you are seeing is the true sh**y nature of interlacing. It sucks. Always has and always will.....

[edDV]

Well you said "Transfered to a PC." Why would one need to transfer to a PC then to a monitor?

But, if anything, what you are seeing is the true sh**y nature of interlacing. It sucks. Always has and always will.....

You are ignoring the benefit of nearly twice as as many channels in the same bandwidth.

Are you saying you would trade half the DirecTV or cable channels for progressive?