Tivo MRV and your home network

January 26th, 2008 · No Comments

Since we now have two Tivos, both later releases than the original series 1, we can now use the Multi-Room Viewing (MRV) feature. That is a feature that allows you to watch something recorded on one Tivo from another Tivo. Meaning you can watch something on your bedroom TV and Tivo even if it was only recorded on your living room Tivo. It’s a pretty cool and EXTREMELY useful idea. But it does have its flaws — like not working as you’d like on a typical home network.

It works best when your Tivos are on a wired network if you’re interested in watching HDTV shows as they transfer. Here’s why. Your Tivo ‘records’ the HDTV show in a compressed and encoded format (that’s how it is broadcast by the networks by the way) which, depending on the quality and detail of the show, generally requires something between 10Mb and 20Mb for each second of show. For you to watch it while it transfers, this means the network between the Tivos has to move 10Mb to 20Mb per second. The initial wireless standard, 802.11b, rated at 11Mbps, has a typical usable bandwidth at something like 4Mbs in the real world when devices are separated by walls like in your and my home. The now common 802.11g, rated at 54Mbs, reaches a maximum usable bandwidth at something like 18Mbs, not quite enough for our purposes, but probably reasonable if you don’t mind waiting a bit after saying you want to watch some HD shows. (Some because not all networks broadcast at the same resolution and quality.) A typical wired connection nowadays is Fast Ethernet, rated for 100Mbs, which gets much more usable bandwidth than that necessary to transfer even HDTV shows as you watch. But how many people have wired ethernet ports at the locations of their TVs and Tivos?

You could upgrade to 802.11n, but it isn’t yet standardized and thus not all devices you might buy are likely to work together. 802.11n is rated at 248MBs and is supposed to have usable bandwidth of about 75Mbs. More than sufficient for transferring HDTV shows while you watch them. So far, we’ve avoided buying these devices because of the lack of standards.

You cold also try alternative wired networking options like IP over power wires (Powernet, Powerline, UPA, etc.) but I’ve heard those also have problems. Like the signals go outside your house and thus others can listen to your network packets. Perhaps you could buy just one and listen to what your neighbors are doing? 🙂 Again, we’ve stayed away from this technology.

In our house currently, we have one Tivo on a wired connection and one on an 802.11g wireless. We can watch about 90% of the shows we want without any network problems, and its a great thing because it effectively means we can record shows on just one Tivo instead of on both. That means we now have 50 effective hours of space to record HD instead of something lower than 30 hours (the Tivo Series 3 can do 30 hours and the Tivo HD can do 20.) And there is no degradation of quality when transferring the shows so HD still looks like HD!

For SDTV (i.e. not HD quality) we have something approaching 500 hours of recording space!!

Tags: Home Theater · IT/Network

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