Does more TVL reduce "Jaggy lines"

[photys 0]

480tvl dome cameras

Geovision gv-800 and gv-1240

Recording high quality, mpeg4 or h.264

 

When I record without de-interlacing, my static images are gorgeous!

Needless to say moving images are torn.

Recording de-interlaced gives me a lot of jaggy lines.

 

If I buy 520tvl cams will this reduce jaggys or is it the DVR?

[survtech 0]

480tvl dome cameras

Geovision gv-800 and gv-1240

Recording high quality, mpeg4 or h.264

 

When I record without de-interlacing, my static images are gorgeous!

Needless to say moving images are torn.

Recording de-interlaced gives me a lot of jaggy lines.

 

If I buy 520tvl cams will this reduce jaggys or is it the DVR?

It's the nature of digitally recording analog, interlaced cameras. You won't be able to get away from it unless you go to digital, progressive scan on all cameras, too.

[photys 0]

Thanks for the reply survtech.

 

 

Just to make sure I have this right.

 

In theory, if TV shows 340TVL then:

A 340TVL progressive scan cam would not show jaggys.

A 2.1 interlaced 680TVL cam would not show jaggys.

 

Have I grasped this?

[survtech 0]

The TVL resolution of the camera or the monitor has nothing to do with the "jaggies". They are caused by the time difference between the odd and even lines of an interlaced picture (1/60 second) after de-interlacing. If there is motion during that 1/60 second, either by the object or the camera, you will see jaggies on the image.

 

DVR's that have higher resolution than CIF (320x240) will show jaggies, but will still have better image quality than CIF. Actually, it's not the first number (320) but the second (240) that makes the difference. So 2CIF (640x240) at 30fps will have pretty much as good a picture as possible when fed with analog cameras with motion.

 

Without motion or with digital progressive scan cameras, the sky is the limit. D1 (720x480) or even higher is possible.

[kensplace 0]

Here is a animation to explain -

 

Image of a moving car captured by a camera, with a lampost on the left for a fixed-point reference. As the car is moving fairly fast, it will have moved between the time the camera captures the first field, and the time it captures the second field. (remember a full frame picture is usually made up out of two feilds, odd and even lines)

 

The animation shows field one, then field two (one field will be all the odd lines, the other all the even lines. You will just have to imagine there is a blank line in between every line in field one and field two)

 

Then it shows them as a DVR rendered them de-interlaced (where it kindof merges the images, but you still get a ghost type effect on fast moving images)

 

Followed by finally the normal interlaced frame which is basically just the odd lines combined with the even lines from field one and field two - this has the jaggies as the car in field on has moved by the time the camera captured/sent field two.... So the car will be in a different position on the odd lines than it was on the even lines, if that makes sense....

 

 

 

as you can see there is a tradeoff, you either can display de-interlaced, but get the motion blur, or display interlaced and get the jaggies or displlay just a field, in which case only half the resolution... (thats not clear on the example though, its just a example!)

 

Some DVR's allow you to record both fields, and then give you the option of viewing either just one field, or both fields interlaced, or both fields de-interlaced - this is a good solution as you can switch views to get the best one depending on the content of the image.

[photys 0]

Thanks for the reply kensplace.

And congratulations on the promotion

 

Bad terminology alert

Sorry, my bad.

 

Its the "jaggy" lines in field 1 and 2 I want to minimize.

They also show on the lampost and the roadside of your image.

Each jaggy seems to be made up of 2 or 3 pixels (horizontal or vertical)

 

I see them on stills at actual size.

 

Are those jagged edges produced by the camera or the DVR

Would a quality DSP or progressive scan camera reduce those jagged edges?

 

survtech

A progressive cam shows no pixelation at actual size?

[rory 0]

thats simply cause you are blowing the image up from its source size.

In other words, if your screen res is 1280x1024, and your video is 640x480 ... when the video is in full single view, it is being enlarged. If you view it at its original size, it is fine, no jaggy edges. Also the jaggy edges should only show on high contrast or bright sections of the image, at least from video i have here on record.

 

Now if the camera is low res also, then its being enlarged even more.

[survtech 0]

survtech

A progressive cam shows no pixelation at actual size?

Any camera will show pixelization if the viewing resolution is increased (blown up) enough. But progressive scan cameras will not show the interlacing jaggies.