Resolution

[Omega]

Hi

Can someone explain what the difference is between CIF and resolutuion. Try as I might I cannot see the difference.

Regards

[james.wilson]

CIF is a resolution

CIF is 360x288 or 360x240.

Pixels that is.

There is no direct way to compare a resolution such as CIF to TVL. That might be what you mean

[Omega]

Thanks for the reply

In fact there are three things that are confusing because they seem (to me) to all refer to the same thing

The way I see it is that a High image quality requires a High resolution which in turn requires a High bitrate.

If ayone of these items is changed then it reflects in the others.

Regards

[james.wilson]

At the moment i still dont understand the question and trying to assume what your asking.

maybe you could clarify the question first?

James

[Omega]

Sorry for the confusion

CIF ..........I believe is a resolution, and to get a better quality picture the resolution can be increased upto D1

Bitrate............... is how fast the pixels are regenerated with information

Image quality ............. speaks for itself.

Now for the confusion, the DVR that I use the Alien has all these options.

Now, if I drop the bitrate will this drop the quality of the image reproduction.

Therefore could I increase Image quality to restore the image quality.

What difference will QCIF make to the image.

What is a suitable bitrate and image quality setting for an average 'in shop setup' to provide trade off with quality against record time.

Regards

[james.wilson]

im the wrong person to ask cos i have a bit of a dislike for mpeg based dvr's. jpeg all the way IMO but

QCIF is Quarter CIF so its a lower res.

You have QCIF, CIF, 2CIF and 4CIF. 2CIF is 700ish x 288.

Bitrate is the max data used in the compression. So if you have a bitrate of say 500K then the max data added will be 500K per second. (500 is a high value for cctv)Mpeg systems are conditional refresh so only the parts of the images that have changed from the previous image are stored. Every so many frames you will have an interframe which is a full screen update. Now if your image isnt changing much ie static internal cam then mpeg can work well as a single target will run through the scene and the bulk of it wont need updating, so you can have nicish images, high framerates etc.

But if its an external camera then when it gets dark the camera image will usually have noise all over the image. This then presents a whole new image everytime so conditional refresh wont help as the whole scene has changed, same with rain and more so with PTZ cameras. Also scenes with larges changes will struggle.

An mpeg recorder will then run upto the bitrate and if the chnage in scene requires more than the bitrate will allow, the compression will increase. This will result in blocky images where the motion is, but the background will not be blocky. But as a rule its this motion your interested in not the back ground.... hence me not being so keen.

But if you set the correct and if the machine will allow high enough bitrates or even better variable bitrate then you can achieve some nice results.

id advise putting everything on maximum and put a bigger hd in it.

[Omega]

Redbull

Thanks for your advice.

This has opened another can of worms but I can deal with this.

Regards