Substream purpose?

[nbstl68]

Sorry if this is a very remedial question but if a given camera can produce only one image/view, what is the purpose of substreams?
I notice some cameras offer several and of different max quality.
The only thing that comes to mind would be a lower quality substream to use when viewing remotely and you dont have good bandwidth available?
When else or for what purpose would I need to connect or record a substream of the same view Im already recording?

(I did just get a fisheye camera that has several substreams but each one allows me to set up a different dewarped view, so in that case it makes sense to me).

 

[nayr]

For the vast majority of people its remote monitoring over weak network connections as you suspect.. few people have internet uploads capable of a single main stream at high quality, let alone multiples; and those lucky bastards that do cant guarantee there mobile connection will have the same speeds.

but they are also used in grid views, If I open 10 main streams in SmartPSS my CPU hits like 300% load and fans kick on full blast.. If I open 10 sub streams in SmartPSS my CPU is at like 70% load, and because they are all little windows there is no quality degradation from using substream vs mainstream.. my NVR OSD does this too and only displays main streams when viewing a single camera, for multiple views its using substreams.

And then you have legacy uses, my LPR camera has the main feed set to 4MP MJPEG @ 25Mbps and I have no desire to record it.. thats used by OpenALPR, but I do record a 720p substream in h264 at a fraction of the storage requirements.

 

[Fastb]

substream is great for remote viewing on cell phone.
The small screen does fine without the high res main stream. Record the hi res to the HDD, high quality footage may help identify folks if needed after package theft, break in, etc.
Low res substream on a phone will look fine, and will be closer to full motion, especially if remote viewing several cams at once.

 

[nbstl68]

Thanks for the detailed answers guys!