SystemQ Posted July 18, 2006 Share Posted July 18, 2006 Brilliant explanation on how it works!!!!!is this how the "STARGATE" works????? Never seen System Q Ltd. Link to comment Share on other sites More sharing options...
arfur mo Posted July 18, 2006 Share Posted July 18, 2006 I assume the dvr has the capability to be controlled via a mouse?? I just have an I/R remote for controlling from the living room nope! the dvr has a remote controller just like a telly, so place the tx bit in front of it and point your remote at the rx bit - its a doddle. B) get mine from maplins. regs alan Hi.JPEG stands for Joint Photographic Experts Group this being the original name of the group that wrote the original standard back in 1992. So to answer your question JPEG is pretty old technology! As the standard was for compressing photographs the compression technique was good but the results depend upon the amount of compression used. When a DVR uses the JPEG technology all it is doing is in effect is storing "photos" from the CCTV camera and playing them back in the correct sequence to provide a moving picture, often know as MJPEG or moving-JPEG (some call it a movie-JPEG) So what the problems with JPEG technology? Well JPEG is "lossy," so the image you see does not contain all the information it did before compression as some of the original information is discarded. Also as a DVR needs to store VAST amount of video information the JPEG compression algorithm isn't good enough as it was only designed to compress the odd photo not millions of images stored on a DVR! JPEG2000 technology (you guest it born in 2000!) is far superior and actually has a If you think education is difficult, try being stupid!!!! Link to comment Share on other sites More sharing options...
Matt the Teckie Posted July 18, 2006 Share Posted July 18, 2006 While we're on the subject of JPEG2000, did you know it's actually the true intended implimentation of Wavelet technology? Don't want to get into the whole MJPEG/MPEG4 debate (there are machines out there now that do both). I tend to fing it's matter of horses (not hippos I'm afraid) for courses. Some like the liniarity and security associated with MJPEG, Some like the transmission advatages of MPEG4 and others like the perceived smoothness of Wavelet/JPEG2000. Personally, I tend to chatigarise compression techniques in terms of application. Remote monitoring - MPEG4 Local monitoring - JPEG2000 High security (likley to be evidential) - MJPEG Home security - MPEG4/AVI Networked (LAN/ADSL) - MPEG4/MJPEG/JPEG2000 Networked (PSDN) - JPEG2000 Link to comment Share on other sites More sharing options...
SystemQ Posted July 18, 2006 Share Posted July 18, 2006 While we're on the subject of JPEG2000, did you know it's actually the true intended implimentation of Wavelet technology? So how do we get to the wavelet then.... ...the original idea behind JPEG was to exploit known limitations of the human eye, mainly that the human eye struggles to perceive small differences in colour change from one area to another. In layman's terms JPEGs work by combining groups of pixels together that are of a similar colour and averaging them in to one colour, as the eye is not too great at spotting this! For example, a group of 4 pixels (all bluish) may be grouped together into a single area that now contains 4 identical pixels (the average blue of them all) so this would be a file 25% of the size of the original. This grouping causes the blurriness you can see in highly compressed JPEG files. Introducing JPEG2000! Eight years latter in at the turn of the millennium, computing power had increased and so had a technology called "wavelets". So in 2000 a new compression star was born; JPEG2000. The technology of JPEG200 again is mainly aimed at photograph compression with the driving force behind it being the increased use of photos on the web. Rather than just improving on the original JPEG compression technique (DCT) the JPEG standards group adopted a completely new "Discrete Wavelet Transformation" (DWT) for JPEG2000. The results are much higher compression with a better quality resultant image. There is even a "loss-less mode". So a new term is introduced, Wavelet! A Wavelet works by analysing an image and converting it into a set of mathematical expressions that can then be decoded by a programme or device such as a DVR. As computing power increases all the time so will the use of wavelets in image compression and in DVR System Q Ltd. Link to comment Share on other sites More sharing options...
jizzer Posted July 18, 2006 Author Share Posted July 18, 2006 So how do we get to the wavelet then.......the original idea behind JPEG was to exploit known limitations of the human eye, mainly that the human eye struggles to perceive small differences in colour change from one area to another. In layman's terms JPEGs work by combining groups of pixels together that are of a similar colour and averaging them in to one colour, as the eye is not too great at spotting this! For example, a group of 4 pixels (all bluish) may be grouped together into a single area that now contains 4 identical pixels (the average blue of them all) so this would be a file 25% of the size of the original. This grouping causes the blurriness you can see in highly compressed JPEG files. Introducing JPEG2000! Eight years latter in at the turn of the millennium, computing power had increased and so had a technology called "wavelets". So in 2000 a new compression star was born; JPEG2000. The technology of JPEG200 again is mainly aimed at photograph compression with the driving force behind it being the increased use of photos on the web. Rather than just improving on the original JPEG compression technique (DCT) the JPEG standards group adopted a completely new "Discrete Wavelet Transformation" (DWT) for JPEG2000. The results are much higher compression with a better quality resultant image. There is even a "loss-less mode". So a new term is introduced, Wavelet! A Wavelet works by analysing an image and converting it into a set of mathematical expressions that can then be decoded by a programme or device such as a DVR. As computing power increases all the time so will the use of wavelets in image compression and in DVR Link to comment Share on other sites More sharing options...
SystemQ Posted July 19, 2006 Share Posted July 19, 2006 Thanks all this information it is appreciated but back to my original question looking at the spec what in your opinion should be the quality of image I am able to obtain with the best settings on this unit should I get an image better than VHS ? as good as dvd ? somewhere in between? i know thare are a lot of variables but lets say with just 1 cam connected maximum frame rate and best compression ... thanks for your time Hi. I have never seen one of these DVR System Q Ltd. Link to comment Share on other sites More sharing options...
Matt the Teckie Posted July 19, 2006 Share Posted July 19, 2006 Hey Paul, got to take issue with the statement that JPEG is more lossy than JPEG2000. (Damn it... didn't want to get sucked into this!) Surely the quality of the JPEG or JPEG2000 image is down to the specific algorithm (not the final format) used to derive the file. As I'm sure you're aware, there are many algorythms used to derive both of these formats. I do concede that JPEG files are generally much larger then JPEG2000, but the pictures are certainly not of a lower quality. It's also much easier to present MJPEG as evidence, mainly as it's been around for so long and doesn't have the predictive conditional refresh characteristics you'd associate with MPEG 1 to 4. In answer to the origional question, unless the DVR can stream data at different compression rates, the picture you see on your computer should be exactly as good as it is when you play back on the main monitor (if not at little better due to the fact that you're not converting the digital signal back into analogue composite video). The only real limitation is down to transmission and process latency. The speed in which each frame can be displayed on you computer screen depends on the bandwidth available accross the physical layer (switches, routers, etc.) and the speed in which the computer can decode and process the data. You may be able to increase performance by applying maximum compression (therefore squeezing a higher volume of files through the Ethernet network) if the problem's the available bandwith. If it's a problem with regard to a very busy computer, it might be worth decreasing the amount of compression. The computer generally doesn't need to work so hard decompressing the image. As always though, there's always a trade off somewhere (even with JPEG2000 ). If you're getting web-cam image quality yet it's a high resolution camera, check the DVR's capture (record) resolution. Hope this helps Link to comment Share on other sites More sharing options...
SystemQ Posted July 19, 2006 Share Posted July 19, 2006 Hey Paul, got to take issue with the statement that JPEG is more lossy than JPEG2000. (Damn it... didn't want to get sucked into this!)Surely the quality of the JPEG or JPEG2000 image is down to the specific algorithm (not the final format) used to derive the file. As I'm sure you're aware, there are many algorythms used to derive both of these formats. I do concede that JPEG files are generally much larger then JPEG2000, but the pictures are certainly not of a lower quality. It's also much easier to present MJPEG as evidence, mainly as it's been around for so long and doesn't have the predictive conditional refresh characteristics you'd associate with MPEG 1 to 4. In answer to the origional question, unless the DVR can stream data at different compression rates, the picture you see on your computer should be exactly as good as it is when you play back on the main monitor (if not at little better due to the fact that you're not converting the digital signal back into analogue composite video). The only real limitation is down to transmission and process latency. The speed in which each frame can be displayed on you computer screen depends on the bandwidth available accross the physical layer (switches, routers, etc.) and the speed in which the computer can decode and process the data. You may be able to increase performance by applying maximum compression (therefore squeezing a higher volume of files through the Ethernet network) if the problem's the available bandwith. If it's a problem with regard to a very busy computer, it might be worth decreasing the amount of compression. The computer generally doesn't need to work so hard decompressing the image. As always though, there's always a trade off somewhere (even with JPEG2000 ). If you're getting web-cam image quality yet it's a high resolution camera, check the DVR's capture (record) resolution. Hope this helps Hi Matt. The JPEG2000 compression algorithm was written to enable better quality images building upon similar principles to that of the JPEG one. However, one criteria of the JPEG2000 design was the option of System Q Ltd. Link to comment Share on other sites More sharing options...
jizzer Posted July 19, 2006 Author Share Posted July 19, 2006 Hi Matt.The JPEG2000 compression algorithm was written to enable better quality images building upon similar principles to that of the JPEG one. However, one criteria of the JPEG2000 design was the option of Link to comment Share on other sites More sharing options...
Matt the Teckie Posted July 20, 2006 Share Posted July 20, 2006 For example if he has a JPEG file of 5k and a JPEG2000 file of 5k, which is the better quality in reproduction of image, the answer JPEG2000 is far superior Agreed. Link to comment Share on other sites More sharing options...
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