The decision to pay the extra fees and move from dial-up to broadband usually involves meeting three wants: faster downloads, faster uploads and live streaming video. The transmission of live streaming video is dependent on bandwidth, video codecs and the ability to transmit as many frames per second as possible. Lets review how these variables effect video on dial-up and broadband. First a little background on bandwidths and speeds. A lot of people use the terms bandwidth and speeds interchangeably, so its important to clarify the difference. Think of a water pipe. You can get more water through the pipe by increasing the pressure to send it through faster. This increases the speed. You can also get more water out the end by increasing the size of the pipe. This increases the bandwidth When you go from a dial-up ISP to a broadband ISP, you increase the size of the pipe by getting more bandwidth. This way you can get more data through the pipe in the same amount of time, thus allowing faster uploads and downloads. Video is data, too, but good video requires enormous amounts of data. Because of this, video is often referred to as a bandwidth hog. When you increase the bandwidth, you allow more video through in the same amount of time. Programmers can use creative and complicated mathematical formulas called algorithms to put the data into packets that allow more packets to go through the pipe. This is comparable to increasing the speed of the water in the pipeline. In the world of video, the algorithm is called a codec. Well known codecs include MPEG-4, MPEG-2 and JPEG. In order to evaluate codecs, a definition of quality is necessary. The number of frames per second (fps) is usually the objective measurement of video quality. Broadcast quality video is an overused term that typically means 25 to 35 fps. Independent of theoretical rates, most live video streamed on the internet through broadband is in the range of 10 to 15 fps. Its not like HDTV or like movies in the theater, but it is sufficient for the purpose. JPEG transmits video like a movie. Each full picture frame from the film strip is transmitted and viewed. When the individual pictures, called frames, are accumulated together rapidly, they appear to display motion, just like a film strip. MPEG-2, MPEG-4 and others dont send a full frame each time. They send whats called an I-Frame, which is a full frame, only once in a while. In between the I-Frames, they only send the video data that change. So, if the image is from a fixed camera in a room where someone is walking, the wall doesnt change, so the image of the wall is not sent with each frame. Only the spots where the person is moving are transmitted between the I-frames. This eliminates a lot of data without changing the quality of the video. So, with the same amount of data, the end result can be more frames per second. This is why MPEG-2 and MPEG-4 are said to offer higher quality video. What is bandwidth? Bandwidth is the amount of data that can be sent in a second, typically measured in kilobits per second (kbps). Did you ever notice how TV reporters on satellite phones sometimes look weird? They are usually transmitting at very low bandwidths of less than 5 fps. Have you asked yourself why cell phone voice plans typically can only transmit still video images, or video clips that are so slow that motion is not apparent? Thats because their maximum bandwidth is 9.6 kbps, also considered very low. Cell phone data plans and dial-up telephone service fall in the less than 56 kbps range. Broadband is above 56 kbps. Cable companies typically offer it in 128 kbps or 256 kbps increments. However, these are maximum rates. For example, dial-up telephone usually fluctuates between 30 and 45 kbps in the real world, even though it is theoretically 56 kbps. MPEG-4 and its many variants are pretty much the standard for sending video over broadband. Many different companies have developed their own unique twist to try to take into account variations in bandwidth that result in interruptions, pixilation and video tears. But, with a 256 kbps bandwidth, video can stream on average at 10 to 15 fps, and may even peak at 20 or 25 fps depending on the fluctuation. Unfortunately, on dial-up, the number of frames per second that these standard codecs can deliver is less than 5 frames per second, and often only 1 frame per second. Some new video codecs are allowing frame rates of 12 fps over dial-up services, in many ways comparable to the video offered over broadband. This has expanded the ability to transmit quality video through dial-up. To summarize the water pipe analogy, different video codecs can increase the water flow by increasing the number of frames per second at the end of the pipe without increasing the size of the pipe. Switching from dial-up to broadband is a way to increase the size of the pipe so that more frames per second can come out the end of the pipe. Cost is always a consideration, with dial-up being less expensive. Also, many people worldwide do not have the availability of broadband, so dial-up is their only option. Comet Video Technologies develops products and services for the low bandwidth transmission of video through satellites, cell voice plans, cell data plans, telephone dial-up and broadband. http://www.cometvt.com Readers have permission to duplicate and distribute the above article in its entirety. We request that the final paragraph be included in each reproduction. |
