Multiple streams

techcanuck

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Basic question here, but why do cameras have multiple streams? First one is HD, second one is usually a lower resolution. If I'm using Blue Iris, how do I ensure I'm getting the HD stream and not the low one? (I used ONVIF discovery)

Not sure if this is related but assuming that BI is already streaming on the HD stream, I am also able to view the camera stream with my web browser (on camera's IP, not BI) at the same time. So it seems the same stream can handle multiple users.... so why would anyone ever use the low quality stream?
 

fenderman

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Basic question here, but why do cameras have multiple streams? First one is HD, second one is usually a lower resolution. If I'm using Blue Iris, how do I ensure I'm getting the HD stream and not the low one? (I used ONVIF discovery)

Not sure if this is related but assuming that BI is already streaming on the HD stream, I am also able to view the camera stream with my web browser (on camera's IP, not BI) at the same time. So it seems the same stream can handle multiple users.... so why would anyone ever use the low quality stream?
if you used onvif discovery it will be the main stream, you can easily tell when you are getting the substream.
There are various reasons for substreams, including most NVR's that display the substream in matrix view to save cpu, mobile viewing, and recording low res to maximize storage.
yes most cameras can handle streaming the main stream to several devices at ones...
 

bp2008

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The "main stream" is the one typically used for recording because it is capable of the best quality. "Sub streams" are usually lower resolution and lower bit rate and are used by many programs and NVRs when they need to show many cameras at once and/or when they need to send streams to a mobile device. When the camera can provide both streams, the NVR doesn't need to do very much processing and it can run on very efficient, low-power hardware.

Blue Iris doesn't really use sub streams (unless you change the camera URL from the main stream to a sub stream, usually by changing a 0 to a 1 or 2 somewhere). Instead, Blue Iris is designed to work with all main streams all the time, and has higher hardware requirements because of it. When you view all your cameras at once, Blue Iris is scaling down the main streams to fit. The same applies when streaming remotely. It would be an insane amount of bandwidth to send full resolution and quality of all cameras over the internet (or even over most wifi) so Blue Iris scales down and re-encodes the video streams as necessary. This isn't as efficient as working with sub streams, hence the higher system requirements, but it is more flexible.
 
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