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Discover Video provides a complete U-verse kit that includes the T1 Router, Ethernet switch, encoder, key wiring and adapters, and install assistance where we work directly with AT&T to make it easy to get "on the air" with U-verse. When you obtain your system from Discover Video, you can have confidence that you are getting a complete solution that has been tested and deployed in the real world, and that you won't suffer from the long-duration troubles found in PC-based systems.
Audio/Video Inputs
The encoder accepts conventional analog composite or S-Video input, and line-level audio input. The audio/video settings in the encoder can be adjusted to improve brightness, contrast, color saturation, hue, etc. and the audio levels can be adjusted. Commonly, it is sufficient to simply "T" the audio/video that is presented to RF modulators, or to use a separate audio/video output from a production switching system.
 Simultaneous Internet Streaming
Discover Video's unique proposition is that our solution delivers simultaneous live streaming of your PEG station on the public Internet. Thanks to built-in advanced routing capability, the Internet streaming uses a conventional public Internet access connection that you already have or can get (consumer DSL service) to push the live video stream at a different rate and resolution to the public Internet. You can see an example here.
About AT&T U-verse
The U-verse system uses Windows Media streaming (a.k.a. "VC-1") to deliver live audio/video to the U-verse subscriber's Set Top Box. Unlike normal television stations, U-verse aggregates all Public, Education, and Government (PEG) channels in a list that subscribers access by manually entering channel 99. This is followed by a "please wait" message for a few seconds while the Set Top Box builds a list of available PEG channels. The list of PEG channels are all of those available in the serving state or region.
Some people believe this is a good thing because it allows subscribers to view many PEG channels, not just those of the local town or community. Some people think it is a bad thing because a viewer must proactively select the desired channel, hence the PEG station may lose "channel surfing" viewers.
Technically, it is a trade-off. There simply would not be enough capacity to give a full numbered channel to every PEG station, and if U-verse followed the analog cable-TV model then only the local PEG stations would be available and subscribers would not be able to see the PEG channels from other towns.
To provision a PEG station, AT&T installs a "T1 line" at the station facility. In some cases, they only install it to what they believe is their "Demark"...which may be in some unusual location. Then it is up to you to run a wire to your station.
A "T1 line" is actually provisioned via a DSL technology and provides exactly 1.536 Mbps of bi-directional capacity. One should not confuse this fact with what is popularly known as consumer DSL service that is asymmetric and provides a high speed download but a low speed upload. The "T1" line is terminated by AT&T with a CSU, commonly from Adtran or a similar T1 access vendor. The CSU ("Channel Service Unit") receives power from the line and presents a "DSX" interface to connection to a router.
The router uses PPP to establish a connection to the AT&T network, using configuration information provided by AT&T. The router is configured such that a range of IP addresses are available, and the encoder is configured to use one of these addresses.
The router is connected to an Ethernet switch, and the encoder is given the target IP address and also connected to the switch. Thus, AT&T can pull the stream from the encoder's server. (Unfortunately, AT&T does not support the push model, which makes setup vastly easier).
One should also realize that the U-verse people and the "T1" people are different. The AT&T people that provision and install the "T1" may think they are giving you public Internet access, and indeed this is what you are getting. The U-verse people then use this new public Internet connection to pull the video into U-verse. Note: do NOT be tempted to use the connection for general Internet access: virtually all of its capacity will be used for video delivery and any other use will likely adversely affect your video performance.
The encoder parameters are unusual, but are optimal for the consumer Set Top Box that U-verse uses. Here are the settings:
- Audio/Video Rate: Approx 1.25 Mbps (AT&T Recommendation)
- Video Rate: 1.1 Mbps
- Audio Rate: 96 Kbps Stereo, 44.1 KHz sampling rate (48K possible too)
- Video Resolution: 480 x 480
- Aspect Ratio: 4x3
There is often confusion around the video rate. Sometimes people say "video rate" when they mean the "payload rate". The "payload rate" is video rate + audio rate + overhead. As already discussed, the maximum rate a "T1" can support is 1.536 Mbps. This number is not the payload rate into the router, however. There is packet overhead (each IP packet has headers that does not carry your data), video overhead (information to keep the audio and video in sync), and depending on the content the video rate can vary a little bit (bursts). You must set the total payload rate from the encoder to under 1.33 Mbps, which leaves approximately 134 Kbps for all of the transmission and video overhead. AT&T recommends 1.25 Mbps rate ("A/V rate"), but this is not the full payload rate which must be under 1.33 Mbps. The encoder video rate could be anything from 20 Kbps to 4 Mbps, and the audio rate could be 8 Kbps to 384 Kbps -- so you must consider both (plus overhead) when you think about the payload rate. Since our intent is to deliver the maximum quality possible within the 1.536 Mbps bandwidth available, we know the optimum settings for the encoder (see above).
Some say it is not possible to deliver a television broadcast at only 1.1 Mbps. The advances in video compression has indeed made this possible, however it is certainly true that a higher quality video image would be produced at a higher bit rate. The quality of the video on the U-verse system is surprisingly good considering the bandwidth used to deliver it, and it often rivals the highly compressed video delivered on satellite and other systems.
The video is encoded and delivered as progressive, square pixel video. This is not to imply the video input is not interlaced...it is conventional NTSC video. The U-verse Set Top Box is optimized to receive this resolution, and it, of course, delivers conventional NTSC interlaced video to the subscriber's TV monitor. No broadcaster should panic or be concerned about the encoder resolution...this is a behind-the-scenes configuration and the result is surprising good (assuming you are using a high quality device such as a VBrick for the encoding).
AT&T uses port 5000 for streaming, and uses no resource identifier. |
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