Internet TV and Bit-Rates

When we hook up our Internet TV box for the first time, we are allowed – in most cases – to set our TV resolution to 1080p. But the reality today is, that this resolution does not by itself state the picture quality.

Such video streams are sent to the receiver in compressed format, and the compressed bit-rate is a more accurate indication of what the actual picture quality will be. I.e., even if the basic format is 1920×1080, by compressing the stream more, lower bit-rates can be achieved, at the expense of picture quality.

Modern Internet TV boxes are quite intelligently programmed, to be able to change the bit-rate in mid-stream. Thus, when my ‘‘ started buffering, during an initial test, it did not only allow for its buffer to catch up with the point in the movie I was watching, but also noted that the real bit-rate of my connection was not high enough to support the highest quality level, available at 1080p. Immediately after that, the picture seemed slightly less sharp, but as I continued to watch, the overall quality of the picture started to recover again.

My has never had a streaming-interruption since then.

In fact, the way it is with HDMI connections to our TV, it is impractical for the source of the stream to change the picture-format in mid-stream. It tends to stay fixed.

And when we compare – which is a service offered by my ISP, also to stream TV to me via DSL – its reason for maintaining a consistent picture-quality is actually different. In this case, the bit-rate of the stream is reserved at the Modem / Router, which also belongs to Bell. I.e., the Bell Modem can ensure that a certain rate of bits per second are available for TV, and can do so at the expense of actual computers also trying to communicate. My is counted by the Bell Modem, as just another connected WiFi client.

What this actually means, is that if another person is considering buying a , but worried that his Internet is not fast enough – as long as he does have some form of high-speed Internet – he need not worry much. The receiver would detect his slow connection, and adjust the picture quality to suit.

Also, with a , we get to set the picture format to 720p instead, so that the required bit-rates start at a slower one.

If my TV was a 4K TV, I could set the format accordingly, but then I would worry, that this might be time and money wasted, because then, the picture quality on my network might not keep up with the 4K format.

Dirk

 

Bell Hub 2000 Idiosyncrasy

It has come to my attention that there exists an idiosyncrasy in the way the Modem/Router of my ISP works, the new modem I was just given, which can lead other Bell customers to confusion.

In its port-forwarding rules, we can select whether we would like to forward a TCP port, a UDP port, or Both. People may habitually choose Both, maybe even because we do not remember which protocol we are using, only which port number it listens on.

If the LAN-computer is only listening on the corresponding UDP port, and we have told this router to forward Both, then an external port scan will tell us, that Both Ports Are Closed. This is because the corresponding TCP port on the LAN machine Is Closed, and because UDP ports generally do not have to report back, when they receive packets. UDP ports are stateless.

Thus, If some people have naively set up an OpenVPN server to listen on the UDP port, but have told the router to forward Both port-types, and if they then try to connect, the failure of the server to respond could have several reasons. But then, if those users ask an external port-scanner to give them the status of the WAN port, the scanner will tell them that the port is closed, and the users may jump to the conclusion, that they are being blocked on the side of the ISP, because obviously, the dedicated port-scanning site would not be blocking them, for the purpose of testing whether their WAN port is in fact listening.

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