Multimedia is the presentation of audio, video, animation, simulation through computer technology. Rather than just static (non-moving) text or images, it provides a dynamic and changing scenario where one can gain a greater appreciation of the subject matter being presented. Unfortunately, a price has to be paid for this added sensation and that price is the processing of large data. All data processed on a web page is digital and is characterized by "bytes" or million of bytes "megabytes" or "mbytes". Text is composed of pages, paragraphs, words and characters where each character represents one byte. A byte is made up of 8 bits where a bit is either 0 or 1. A picture is made up of a lot of dots or "pixels" where each pixel represents one, two or four bytes depending on the amount of color memory (8-bits per pixel is one byte, 24-bits per pixel is three bytes, etc.). A small picture, e.g., 100 x 100, contains 10,000 pixels and therefore requires 10,000 (10K), 20K or 40K to represent it, depending once again on the color depth (8-bits/pixel, etc.). A page of text, on the other hand, has about 600 characters or 600 bytes (less than 1K) and therefore much less than an image.
When you transfer text or images over the network, pictures or text or a combination are collected and packaged and submitted as bits or bytes or megabytes. The speed at which this data arrives is a function of the speed of all servers involved including the host (in this case LaxPower), the intermediate servers, and finally the receiver (that's you), where you have a device, usually a modem, which transfers data from a telephone line into your computer memory or fast-memory (cache). A modem that is 28K transfers 28,000 bits per second. A modem that is 56K transfers at twice the rate and therefore downloads pages twice as fast. Systems that run at companies or at school usually run on high- speed "T-1" lines which is approximately 30 times faster than a 56K modem. So these privileged people get data very quickly.
Slower systems can handle text without too much problem. When you introduce graphics, then slower systems do not respond well, whereas faster systems do just fine, e.g., a wait of only a few seconds. Now when you start talking about audio and video, you're talking large data of many megabytes which can take a long time, e.g., 5-10 seconds per mbyte on a T-1 and 1-5 minutes on a 28K-56K modem. A video is nothing more than digital data representing a collection of images (and sound), so if you have 24 frames/sec and 30 seconds of video, you're talking 720 images * 20K (or 10K or 40K), which is many mbytes and which is impractical. This is why you don't see a whole lot of videos on web pages.
For lacrosse, though, it's important to try and get videos and/or sound because they provide a more meaningful experience of an event or happening. So how do we send you a 25 mbyte video that you can receive in seconds or a couple of minutes instead of a half hour which most people will not have the patience to wait for? We employ tricks and compromises!
Tricks and compromises to reduce data:
We welcome any feedback on the following:
Tags:Tips blog, tips Multimedia, Trick Hacking tips facebook, internet, Info Teknologi,
When you transfer text or images over the network, pictures or text or a combination are collected and packaged and submitted as bits or bytes or megabytes. The speed at which this data arrives is a function of the speed of all servers involved including the host (in this case LaxPower), the intermediate servers, and finally the receiver (that's you), where you have a device, usually a modem, which transfers data from a telephone line into your computer memory or fast-memory (cache). A modem that is 28K transfers 28,000 bits per second. A modem that is 56K transfers at twice the rate and therefore downloads pages twice as fast. Systems that run at companies or at school usually run on high- speed "T-1" lines which is approximately 30 times faster than a 56K modem. So these privileged people get data very quickly.
Slower systems can handle text without too much problem. When you introduce graphics, then slower systems do not respond well, whereas faster systems do just fine, e.g., a wait of only a few seconds. Now when you start talking about audio and video, you're talking large data of many megabytes which can take a long time, e.g., 5-10 seconds per mbyte on a T-1 and 1-5 minutes on a 28K-56K modem. A video is nothing more than digital data representing a collection of images (and sound), so if you have 24 frames/sec and 30 seconds of video, you're talking 720 images * 20K (or 10K or 40K), which is many mbytes and which is impractical. This is why you don't see a whole lot of videos on web pages.
For lacrosse, though, it's important to try and get videos and/or sound because they provide a more meaningful experience of an event or happening. So how do we send you a 25 mbyte video that you can receive in seconds or a couple of minutes instead of a half hour which most people will not have the patience to wait for? We employ tricks and compromises!
Tricks and compromises to reduce data:
- We employ a technique called data compression. Compression in very simplistic terms collects data that have the same characteristics and represents them only once and not multiple times. As an example, instead of collecting every pixel on an image and storing its value, why not just collect the first pixel and if its value does not change, just count the number of consecutive pixels and store that number? If an image contains mostly background (e.g., black), then it would be foolish to store thousands of bytes containing "0" when you could just represent this by just a few bytes. Also when storing video, why not subtract data from the next image instead of storing each pixel again? Compression can reduce images from 50 megabytes down to 1 or 2 megabytes. When you receive compressed data, the applications which run your program will be able to "decompress" this data on the fly and you will not know the difference.
- We reduce the size of the images. It would be nice to run full-screen images of videos but the data size would be unmanageable. The smaller the size, the less the data. As an example, a 400 x 400 image contains 160,000 pixels, but a 200 x 200 image contains only 40,000 pixels or 1/4 the size. Thus if you are disappointed with the size, would you rather wait four times longer to download this large amount of data? Does your system have the memory capacity to handle that much data?
- We reduce the number of colors or go monochromatic (grey scale) which could also reduce the file size to 1/2 or 1/4.
- We use the lowest sound resolution which hopefully will not affect the quality of sound output. We may in some cases eliminate sound altogether.
- We reduce the video frame rate (keeping the sound at its current rate). If you watch a video at 5, 10 or 15 frames, there is a loss in continuity for the 30 frames/sec that you are accustomed to, but sometimes it is perfectly acceptable, especially if it means viewing or not viewing the video. I have even run 2 minutes of video at one frame per second with the audio at 30 frames/sec and have found that I captured the essence of the event and reduced the data to the 1 megabyte range.
- We crop or cut out the peripheral part of the scene that does not add significantly to the content.
- We get a faster modem or faster servers which will be happening in the near future.
We welcome any feedback on the following:
- Is the image/sound quality acceptable?
- How long did it take to download the video?
- Did you maximize to full screen? Was that better viewing?
- Did you automatically play the video from an application on your system or did you have to download a helper application from the web?
- What is your modem's speed? 56K?
- Who is your server? AOL? School dormitory? etc.
Tags:Tips blog, tips Multimedia, Trick Hacking tips facebook, internet, Info Teknologi,
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