The Custom Integrator Show Installment 00E

The Custom Integrator Show Installment 00E is live.  We expand upon our discussions of the home networking hardware and Ethernet switch considerations that we touched on in the last installment.  In addition, we take a little deeper look at not only bandwidth requirements for different devices and content streams, we discuss the influence of physical cabling types and some of the wiring techniques that can influence getting those streams around the home efficiently.

[mp3]http://blip.tv/file/get/IanDixon-TheCustomIntegratorShow00E867.mp3[/mp3]

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The concept of our initial focus is that, with any stream, there really are four factors that influence how many bits per second are required to move the data around – resolution, frame rate, color depth, and the amount and type of compression.  The easiest example to put some numbers around is a “basic” IP-based surveillance video camera.  We will leave out the color depth aspect to keep it simple and will assume that the camera is transmitting a “reasonable” VGA image with a JPEG compression scheme.  That gives us about 30 KB (that’s 30,000 Kilo Bytes) per frame.  We then need to multiply that times 8 to get to bits per frame, so we are dealing with about 240,000 bits (240 Kb) of bandwidth needed per frame of video sent.  We will assume, for this example, that we will send 30 frames per second (based upon the US 60 Hz standard for video – it would be 25 fps for Ian because of their using 50 Hz for their power line frequency).  Note that Hollywood is using 24 fps for most of the film work for formats like many of the Blu-ray Discs, but that really does not come into play for this example.  Also note that you normally can use a much lower frame rate for most surveillance scenarios, but we will stick with 30 fps for this.  Therefore, we multiply the 240 Kb per frame times 30 fps to end up with 7,200 Kilobits per second, or about 7.1 Mb for one second of video – and that is for a single camera.  You can see where having five or ten cameras constantly sending video over your IP network can start to have a significant impact on the overall bandwidth requirements, even without the high definition streams. 

If we take a look at some of the bandwidth requirements for a wider array of high definition material, things start to add up even more.  Notice the impact of the levels of compression on different sources of material.  Naturally, this impacts the perceived picture quality, even for the same resolution.

• Blu-ray H.264/MPEG2 at 1920×1080 1080i/p about 40 Mb/s
• ATSC HDTV MPEG2 at 1920×1080 1080i about 19.39 Mb/s
• Digital Cable MPEG2 at 1920×1080 1080i about 16 MB/s
• DIRECTV HD MPEG2/MPEG4 at 1920×1080 less than 10 Mb/s
• Xbox Live Video VC-1 at 1280×720 720p about 6.8 Mb/s
• DVD MPEG2 at 720×480 480i about 8 Mb/s
• Apple iTunes Quicktime/H.264 at 1280×720 720p about 4 Mb/s
• Web “HD” downloads H.264 at 1280×720 720p about 1.5 Mb/s
• HD DVCPRO (home movies) comes in at about 100 Mb/s!
• 1920×1080/60i 4:2:0 is a whopping 932 Mb/s

Remember that you need to take into account the aggregated bandwidth requirements of all of the different types of streams potentially playing simultaneously to all devices within the home.  Add in copying files and/or transmitting high resolution images to picture frames and it really starts to add up.  As we note in the Podcasts though, it is not just about bits per second.  The real issue is that this is all timing-sensitive information and the bits need to arrive in order with no latency, jitter, or reties.  Putting in a solid cable plant with all of the appropriate equipment for achieving that takes a lot of up-front planning and work to be successful.

Another consideration, especially when looking at how to configure traffic prioritization manually for the overall Quality of Experience (QoE) of the network, is that many families now are using their network for all of their phone and audio traffic, too.  If you try to accommodate Quality of Service (QoS) for the high definition streams, you cannot do it at the expense of the audio.  Things get even more complicated when you start streaming audio around for a multi room IP-based audio system.  It takes a lot of effort and insight to get it right.

We talk about some of the new IEEE standards on the horizon that could influence your equipment purchasing criteria like the IEEE 802.1 AVB (Audio/Video Bridging Transport Protocol) and IEEE 1722 specs at http://www.ieee802.org/1/pages/avbridges.html.  We also mention the IEEE 802.11aa specs for wireless video transport streams (although, once again, we discourage the use of this type of wireless for the infrastructure components).  There is a good time line for when these may hit at http://www.ieee802.org/11/Reports/802.11_Timelines.htm.  They may seem like they are a while out, but it never is too early to start understanding them and the impact they may have on your designs.

As always, ALWAYS document your systems, especially the static IP addresses of all of the infrastructure devices on the network.  I mention a couple of tools we have found useful for doing this.  One is the Colasoft MAC address scanner at http://www.colasoft.com/ (you can start with the free one under Downloads off of the main pull-down menu).  There are others, but we have had good luck with this one.  They have several other nice products for purchase.  Another is the network mapping utility for Visio from SolarWinds called LAN Surveyor Express at http://www.solarwinds.com/products/LANsurveyorExpress/.  They have a free trial available.

I thought Digital Cable Tuners and CableCARDs would draw a lot of interest.  Based on the site numbers so far, the last installment on home networking Ethernet hardware considerations has the highest number of views yet.  I find it interesting that there were no comments from any of you regarding the questions I posted for the last installment (Installment 00D).  I really would like to see a couple of takers share their in-field experiences for the good of the community.  In an effort to try to keep that moving forward, I am going to break the topics out a little more so they are not quite as intimidating in hopes that a couple of threads might start up.  Keep an eye out on this blog site over the next week or so as I re-post some of that information in a different format.

In the next Installment, we will take a look at some of the tests to try before turning the system over and some troubleshooting approaches to isolating network related issues.  We also will hear about Ian’s experiences with his power line network, so stay tuned.

  =D-