thecctvcompany

Hi Can one connect a 1080P SDI camera to a 720P DVR and still get acceptable recording performance? I know that the answer should be 'yes' but am not sure of the technical implications here. Obviously 1080P has a higher bitrate than 720P to start with. Seeing that SDI DVRs do the decoding at the DVR end, it means that the DVR has to work hard and becomes more expensive as the channels rise. However, if one has a 720P DVR and it receives a 1080P stream, does it just drop frames, or does it do the decoding and simply convert the 1080P stream to an internal 720P stream? What are the reasons why one would not want to do this? The cost of a 1080P DVR is quite a bit higher than a 720P DVR. However, there is little difference in cost between 720P and 1080P SDI cameras. So it makes sense for us to buy 1080P SDI cameras so that they can be connected to a range of DVRs Thanks!

SunnyKim, thank you for your input and technical explanation. This has been most helpful to us. Thanks again for taking the time out to engage with us and deal with the technical issues we are interested in understanding! We really appreciate this Regards Clive

SunnyKim, that is an intelligent reply. Thanks for that. It is what I suspected. We suspect that the 720P DVR is able to decode the 1080P stream but at a reduced frame rate. So instead of getting maybe 25fps, we may need to throttle back to 12 or 15fps which will not make a big difference anyway in the site where this will be installed. From what you say, there seems to be two stages in the decoding process? The video receiver and the SDI decoder. You may need to assist with clarifying this.... <> The raw bitstreams comes in at 1080P on the BNC connectors at the back. Then each BNC connector feeds into a SDI decoder ('BT1120')? Or are 2 or more BNC inputs combined into a single SDI decoder? Then the DVR software sits on top of this hardware and manages the receiving streams and passes it to both the HDD and monitor screens. Am I correct in thinking then that the capability to push 1080P into a 720P DVR depends on the manufacturer of the DVR and what provision they have made for high speed decoding?

We have tried it and it does work. We tested it on 4 channels only but now want to move to a 16 channel system. ie, we ran 4 x 1080P SDI cameras into a 720P DVR and it worked fine. We are more interested in the technical reason why and why not this may or may not be a good idea. Also what the risk issues are when we connect 1080P cams to a 720P DVR We just don't want to embark on a technology mismatch that will come and bite us later. Yes, I take the point about the chipsets and in the end this may be a capability of the DVR itself. It may be that some suppliers' DVRs will simply not work and others will. We are keen to know if anyone else has tried this and what the outcome was.