Video/Audio Signal Distribution Via 802.11g?

Discussion in 'Home Theater Projects' started by aeveritt, Jan 19, 2005.

  1. aeveritt

    aeveritt Agent

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    Several months ago, I saw a portable television that Sharp had introduced that utilized 802.11b wireless to transmit a digital signal from a base unit to the television.

    At first, this seemed similar in operation to the audio/video wireless sending units that most everyone is familiar with. The picture quality, however, was crystal clear. Most of the other audio/video sending units I have seen transmit a 'fuzzy' analog signal, especially as you add distance or walls to the picture. The Sharp, utilizing an 802.11b digital signal was rather impressive. However, the price was rather high, I thought, for what it was.

    What I would like to do is either purchase or somehow manufacture a device that will take video and or audio signals, encode them and transmit them utilizing 802.11b or 802.11g wireless protocols to another receiving unit that could then be connected to a regular television. I know I have seen home media devices that will transmit files from your computer, etc. but is there something that will encode MPEG streams from sources on-the-fly and transmit them like the Sharp unit does?
     
  2. Rob Bird

    Rob Bird Agent

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    Yes, you can get an mpeg encoder card for a computer and do it. I am considering doing that with a Nano-ITX motherboard when they are available. The QoS probably isn't an issue with those data stream sizes, but you are going to want to implement priority queues if you have people actually using the wireless for other data at the same time as the streaming frequently. I won't get into all this unless there is a lot more interest [​IMG] it could get a bit tedious (and replicant of other forums and sites), but doing variable bit rate streaming with a data type that doesn't respond well to drops isn't very smart on a medium like wireless..
     
  3. Sami Kallio

    Sami Kallio Screenwriter

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    My experience with 802.11g (and b) network is that they are prone to drop packages so playback can pause once in a while. I wouldn't plan it for DVD playback at all, Divx and other more compressed formats probably would be ok.
     
  4. Rob Bird

    Rob Bird Agent

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    Yeah, basically, real time video is highly intollerant of drops (meaning, packets that are lost/corrupted/etc.). Drops = lost images, because you can't go back after the fact and get back what you lost (you've already passed the scene). It's a variable bit rate (VBR) service because the data rate typically varies. This is in contrast to voice which is a constant bit rate (CBR) service that uses a stream which is always the same size. The problem with using wireless for things like digital video is that the bandwidth is shared and can't be guaranteed for your video application.

    The best way to do it would be to use a wireless access point with a channel dedicated just to your video needs. Use another one for any data. This means more access points, but you'll at least have a good chance at good quality. I would also use 802.11g...the 11 Megabits of .11b is best effort. In reality, you'll get a fraction of that. We usually consider anything more than 2-3 Megabits/sec on .11b to be gravy. You'll want up to 10 for assurance on mpeg4.

    Here are the NanoITX motherboards I was talking about. A couple of these can form the foundation of the devices you are looking at. Unless you must have wireless, I'd just use 100Mb ethernet...it's more than adequate, much more reliable than the wireless and far cheaper (it's also built-in to these boards). These motherboards are only about 5"x5" and come with an embedded ultra low power CPU.
    http://www.viaembedded.com/product/e...herboardId=221
     
  5. ryan_m

    ryan_m Stunt Coordinator

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    I've been interested in doing the same thing, want to be able to watch/control my Tivo in another room (on a different floor). I happened to stumble on the Belkin Pure AV RemoteTV on cnet. It looks pretty perfect but is way to expensive at $500. Just thought I'd share. I'm still looking for a cheaper way of doing it. Just found this also: wireless-avw-1000 .

    seeya
    Ryan
     
  6. aeveritt

    aeveritt Agent

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    The Belkin unit is essentially what I've been looking for. Thanks for pointing this out. Looks like it transmits up to a 40mbs signal utilizing a proprietary wireless protocol. It's expensive for what it does though. It looks like I'd have to pay somewhere in the neighborhood of $450 for it. I did a little searching and it looks like this is only a few months old. If/when I can find it for $300 or less I'll probably grab one.

    The other product at Ram Electronics, I believe, is just another analog RF transmitter/receiver set that will likely produce a mediocre picture, at best.
     

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