MPEG4 on DVR. Quality issues

[Guest Rockford]

We have installed a few DVRs that allow the recorded images to be played/viewed in 'Windows Media Player'.

On some machines, the playback is fine whilst on others, it's poor with very limited colur and shading. A simple 'CODEC' download installed into WMP increased image quality.

I'm not entirely sure but these 'CODECs' may need to be installed onto the host playback PC even if the recorded CD has it's own viewing software to run in.

A shot in the dark post that may aid. Worth a try as the 'Windows Media Player' option on our 'Flat-Tec' models had the image quality increase considerably after installation of an MPEG4 Codec.

69326[/snapback]

Well, at the moment we're recording using the MS MPEG4 codec. Of course, if one were to use an MJPEG codec the quality would improve, but the issue here is that I have two sites using the SAME DVR with the SAME codec; the cameras give the SAME quality feed on a composite monitor and only ONE of the two sites gives poor quality when cameras are connected. We've replaced the DVR with another the SAME and it ALSO gives dodgy quality. That's the issue. I don't know what to do about that...

[Rich]

If you don't know the TVL of the cameras or resolution, post the makes and models of the cameras connected to both DVR's and the make/model of the DVR's.

If you are using low resolution cameras on one site and high resolution cameras on the other, depending on the TVL of the CRT Monitor you are using, you may not notice the difference between camera image quality, for example a 450TVL camera on a 450TVL Monitor will display true, A 550 TVL camera on the same monitor will display under resolution at 450 TVL. I think from what you are saying and the conclusion you are leaning towards is the dvr's are recording at a high resolution which clearly shows up the low resolution cameras.

Basically, TVL is more commonly used with DVR's because it relates closely to pixels. A Television line (TVL) is basically the vertical line of a PAL image.

A CRT Monitor projects a beam of light left to right across the screen and its TVL can be measured in the amount of times it can create the smallest image possible to its neighbours, for example black and white, where (.= black and |= white) .|.|.|.|.|.|.|.|.|.|.|.|.|.| would be 28 TVL

When we talk about DVR's we use pixel dimensions because PC monitors and computers work in pixels to display an image.

When you review the recordings on your PC next, change the actual screen size of the video image and see if at any point it starts to look sharp, and compare it to one of the better images, this will give you a bit more of an idea of how much more information you get from a hi-res camera compared to a low-res.

Let us know what you find.

[Doktor Jon]

Rockford,

Just a thought but you mentioned that there are two different quality cameras on each site.

For whatever reason (e.g. camera level output, quality of cable, connections, power supply etc.) , have you excluded the possibility that the 'poor quality' set up, may be as a result of a reduced signal level reaching the DVR?

This would normally be tolerated and displayed o.k. by a CRT monitor, but could be problematic with the DVR.

Perhaps try using another temporary replacement high quality camera to test with the existing cable run, or take down the 'offending' (?) camera and connect it directly to the DVR with a short test lead.

Even if it doesn't solve the problem, at least it will give you a couple more bits of the jigsaw (I know I shouldn't, but I'm assuming that you haven't tried this already).

[Guest paraffinlamps]

I would tend to agree with Doktor Jon .

I have experienced similar problems myself and find that DVR`s need a very good signal in .

I would check the video signal at the dvr, also may be worth checking the colourburst.

Some camera manafacturers differ in their output signal ,Pelco for example is slightly higher than 1v p2p.

Also what is the cable run like on the poorer quality one and what type of cable .

Recently I have experienced problems when companies I work for use copper covered RG59 as opposed to pure copper .The difference to dvr`s is amazing.

HTH

Lamps

[Guest Rockford]

Rockford,

Just a thought but you mentioned that there are two different quality cameras on each site.

For whatever reason (e.g. camera level output, quality of cable, connections, power supply etc.) , have you excluded the possibility that the 'poor quality' set up, may be as a result of a reduced signal level reaching the DVR?

This would normally be tolerated and displayed o.k. by a CRT monitor, but could be problematic with the DVR.

Perhaps try using another temporary replacement high quality camera to test with the existing cable run, or take down the 'offending' (?) camera and connect it directly to the DVR with a short test lead.

Even if it doesn't solve the problem, at least it will give you a couple more bits of the jigsaw (I know I shouldn't, but I'm assuming that you haven't tried this already).

69434[/snapback]

We haven't tried this yet but you're right, we really should have! The cable reads out OK if we use a meter, but that's no substitute really! We'll try. Excellent advice, thank you!

[Guest Lee Tracey]

OK, we have a client who has a PC based DVR that uses MPEG4 as its compression codec.

They have a camera looking at a street on quite a wide viewing angle on which the picture quality is quite poor, though it looks perfect on a composite monitor.

we have another customer on the SAME model unit with a MUCH more expensive camera (has a bigger lens) ALSO on quite a wide view and the picture quality is much better, though that said, the two look the same in terms of quality on a composite monitor.

Could it be the lens size that's causing the difference or what?

Thanks for any and all advice from everyone!

The problem is the DVR. The monitor when displaying live will show you the quality of the camera, the cable and the monitor. Buit what matters is the recovered from DVR hard drive image quality. That will be between 80% and 35% worse than the live quality. Each DVR gives a different performance.

Lee Tracey