Dual Stream Camera: Why?

This is a very general question. Desired result is help in answering a question inside my office. We live monitor accounts for a fee; loosley vsaas. This is a service we offer in house (not sold to 3rd party monitoring company) along with full integration service etc...Historically we have stuck to one manufacturer because we know how to manage the data streams (important for managing more than 6000 cams daily in the field) and we do dual stream (1 to on site DVR 2nd to our monitoring center, or at least that is my understanding. I am a salesman so please forgive technical lack of knowledge etc.)

ANYWAY, we recenlty started testing some new cameras and their is an argument to whether we need dual stream or not. ANY and all theory and explanation of the dual stream concept will be greatly appreciated as there is not anyone in our office that is enough of an authority to answer it definitively. I am sure members of this site have the knowledge base to educate us and answer the question.

I think you have a good understanding of an ideal 'dual streaming' application. Here's why it helps:

  • Bandwidth

The first stream (the one flowing to your monitoring center) is presumably lower FPS/higher compressed/lower resolution than the second stream flowing to the NVR.

Since the live video is uploaded to the internet and to a remote site, smaller bandwidth means less expensive internet connections, etc.

The second stream (to the local storage recorder) is likely much more bandwidth, but higher FPS/lower compression/higher resolution. Since local storage means bandwidth in not restricted by an ISP (and transported a comparatively short distance), it makes sense to use more bandwidth.

Presumably, if some event is noticed remotely by the monitoring staff, they can download or review the 'higher quality' recording from onsite storage. They can do this only when needed, so 'dual streaming' helps make things more economical.

That's just one angle to this, and if there are more questions, just ask!

Thanks, Brian

I took and passed (got certified) one of the IP cam basics classes you taught. The answer you gsave me is the answer I gave our team almost verbatim...however, I qualified it with, "This is my understanding of it." And, I thought I did understand dual stream as a fairly simple thing. What you described is exactly what we do. I was a monitor, monitoring manager, and then video review manager before I became a salesman. But, all that answer got me was an incredulous look from the group and one of the IT guys said there is more to it and maybe we don't need dual stream cameras. I do not know all of the offerings in the IP market but I thought dual stream was a fairly ubiquitous and beneficial option...The point of their whole conversation was that they were trying to tell the owner that dual stream cameras were no longer necessary. Concern stemming from potentially using different than our usual cameras on the VMS platform we use. My understanding is that we would need dual stream to remotely monitor regardless of the VMS because of the bandwidth issue.

By they way, they came and asked me what I knew about dual stream because, "I seem to have a lot of IP cam knowledge." I don't, I know I don't. What bothers me is their potential lack of knowledge by thinking I have a lot. And, they are talking about using the high stream (less compressed stream) from a 5mp Acti E38A to remotely monitor. They said the testing (after one day) was not spitting out that much data in the high stream. I have a feeling they don't have the cam configured in a way and/or in a scene that is giving good data.

Is there more to it from another angle that I don't understand... or is it that simple in total? I am lost and worried that they may steer our ownership in a direction where they really don't know what they are talking about.

Thanks for your time,


There are a few things you need to look at immediately, if you have left that Acti camera at its default settings:

1. The Acti E38 is a 2mp camera, not 5 mp. You mention the E38a but i can't find any reference to this model, only the E38.

2. By default, all Acti cameras ship at 1mp enabled. I don't know why that is but even a 5 mp camera is not at 5mp by default with Acti, you must change the resolution to get 5mp.

3. It is quite possible that this 5mp camera is transmitting at its default 1 mp setting and that is why they find the bandwidth quite reasonable (i think the second stream also defaults to 1mp).

4. You should also verify the bit rate- i think that the Acti is Fixed bit rate by default but that the quality setting is low by default. You can definitely crank up the quality settings (and the bandwidth requirements) from the default

err, E83a, sorry

ok, that makes more sense. The points 2 to 4 above are still valid for the E83a - if you did not change the cameras from default, they would be at 1280 x 720 for the first stream.

Thanks a ton, Undis B!

Undi B,

yep, 2 and 3 solved a big chunk of it. Thanks for the knowledge. Very good things to know.

IPVM did a full mulsti-streaming test and review of VMS' that actively use it for everything from bandwidth optimization to server-side advanced motion detection.

VMS Multi-streaming Comparison

Thanks so much Nathan!

Another benefit of multi-streaming is that most PCs (usually onsite) can not handle either video card or CPU decoding many high megapixel cameras at once. The system chokes when you display 16+FullHD or 3Mp or 5Mp cameras at once. In addition, the monitor resolution does not allow you to see the full detail. Also, many camera at these high megapixels do not show 30 frames per second. Thus, monitor can look choppy and hard to watch.

By using a second stream, you lower the load the PC has in addition to the bandwidth, and can view a high frame rate, low bandwidth stream.

I also like to set up 1 stream for live viewing, 1 for recording, 1 for SD card recording, and 1 for mobile access. This way, changing a setting for 1 stream doesnt effect another stream.

Many cameras can now push out 6-10 unique streams.


"Many cameras can now push out 6-10 unique streams." - what manufacturer does this?

Most Samsung cameras can have 10 streams or profiles available. They ship with 1 MJPEG, 1 H.264, & 1 low res MJPEG mobile profile. The first two can not be deleted, but can be modified, except for the codec. Each profile can select their unique codec, resolution/aspect ratio, frame rate, compression, bit rate, bit rate mode, unicast/multicast, crop area, audio in, profile, entropy encoding, ROI compression, GOV length to name a few settings.

I personally have used a max of about 6 streams. I used multi-cropping to select a few virtual cameras, then 1 record stream, 1 edge recording stream, and a mobile stream.

That being said, any of these could have been an edge recording stream, or mobile, but sometimes it is nice to keep them seperated so one change does not impact another...

Some confusion might come from memorized profiles inside the camera (combination of pre settings) that you can call by cgi commands, Axis is doing since the begining, and real simultaneous multiple streams ... some cameras share their CPU to try to deliver the maximum, fps and res + motion + wdr + .., but sometimes you will never get what you expect, because ... it won't even leave the Ethernet interface ..... (some cameras tells you I send 70 Mbits, but when you measure it ... you get 45 Mbit max..)

Some TW companies like Acti, but also Merit Lilin offer "hiddden profiles"inside the stream so that they claim they can reach very good bandwidth levels by over compressing (putting a low hidden CBR) and putting some very long Gop.