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What is MPEG-4? |
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In March 1999, Moving Pictures Expert Group Phase 4 (MPEG-4) was established as an international standard encoding method for moving images. This latest moving picture compression technology achieves super low bit rates (high compression ratios) of less than 64Kbps. |
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What is ASF? |
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Advanced Streaming Format (ASF) is Microsoft® Corporation's next generation multimedia file format. Files using this format can be played back using Windows® Media Player. |
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What does bit rate mean? | ||||||||||||||||||
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Bit rate is the amount of data that is sent over a given period of time. MPEG-4 data consists of four types of information: resolution, frame compression, time compression, and frame rate. A bit rate of 64Kbps sends 64 kilobits of data per second. | ||||||||||||||||||
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What does frame rate mean? | ||||||||||||||||||
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Frame rate is the number of frames (still frames) per second that appear in a given amount of time. The MPEG-4 compression method, which is employed by the Internet ViewCam, uses a variable frame rate playback method to reproduce optimal quality images according to the playback environment. This allows for smooth moving picture playback using less memory. | ||||||||||||||||||
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What does streaming mean? |
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Conventional moving picture formats require that the entire file be downloaded before playback can begin. With streaming technology, however, a moving picture clip can be viewed almost simultaneously as it is being downloaded. It is even possible to pause the clip at any time during playback. Streaming playback is possible from an ordinary HTTP server or a NetShow server.
*Notes: During actual playback, moving picture clips may drop to a lower frame rate or stop temporarily due to the playback buffer. |
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How can I get Windows® Media Player? | ||||||||||||||
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You can obtain Windows® Media Player using any one of the following methods: | ||||||||||||||
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How are ASF files played back when arranged in HTML format? |
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The following is an example of HTML code for linking an ASF file: <A HREF = "movm001.asf"> ASF file 1 </A> |
| In this case, the file name "ASF file 1" becomes an underlined link displayed in color. By clicking on this link, the browser launches an application that is relevant to the file. In most cases, Windows® Media Player is the application relevant to the extension "ASF". If Windows® Media Player is installed in your computer, clicking the "ASF file 1" link automatically launches the application and plays back the moving picture file. |
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How can I create effective Web sites with streaming playback? | |
| 1. Confirm the MIME settings of your provider. | ||
| 2. Create an ASX file and incorporate it in an HTML file. | ||
| ...<Creating an ASX file> <Making a link of an ASX file> | ||
| 3. Prepare an ASF file in LP mode for streaming playback. | ||
| 4. Other notes | ||
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Confirm the MIME settings of your provider. |
| Unlike Internet Explorer, Netscape browsers cannot play back ASF files unless the provider that hosts the Web site makes MIME settings for ASF files. When placing ASF files on your Web site, keep in mind that many visitors to your site may be using Netscape, and request your provider to make MIME settings. (It is necessary to make a setting of MIME type "video/x-ms-asf" for two file formats, extensions ".asf" and ".asx".) | |
| Click here for information on detailed MIME type settings of ASF files.
* URL may change without prior notice. |
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Create an ASX file and incorporate it in an HTML file. | |||||
| When an ASF file is placed in the HTML file, Netscape browsers create a temporary file on the hard disk to save the specified ASF file. Windows® Media Player plays back the temporary file. Consequently, it takes time to download the entire file. The "ASX" file format is used to enable complete streaming playback. | ||||||
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| AAA | <Creating an ASX file> |
| ASX is a simple text file that can be created and edited using text editing applications such as "Memo Pad". Following is an example of the content of an ASX file (file name: movm001.asx) that plays back "movem001.asf" located at "http://sundaynet.ne.jp/joho/sakoh". | |
| <ASX version ="3.0"> <Entry> <Ref href="http://sundaynet.ne.jp/joho/sakoh/movem001.asf"/> </Entry> </ASX> | |
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1st line: Always use the number of the latest version. 3rd line: Describe the location of the ASF file using an absolute pass. You should not use a relative pass. When a relative pass is used, you cannot open files using a Netscape browser. |
| . | <Making a link of an ASX file> |
| The procedure is the same as that for still images. | |
| <A HREF="movm001.asx">ASX file 1</A> | |
| In this case, you don't have to use an absolute pass. |
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Prepare an ASF file in LP mode for streaming playback. | |||
| Streaming playback of ASF files with a bit rate of more than 64Kbps (moving pictures recorded at a rate higher than Normal mode) requires a data transmission speed of more than 64Kbps. A high data transmission speed is not always guaranteed, however, because network conditions constantly change. This is due to provider conditions as well as your modem's capability. Moving pictures in Normal mode (64Kbps) can be viewed reliably with bulk transmission modes such as Dual ISDN. | ||||
The following procedure shows how to increase the frame rate of moving pictures recorded in LP mode.
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| You can also place a link to a moving picture file recorded at a rate higher than Normal mode, and have visitors to your Web site download it with the right mouse button. This way, visitors can quickly view your moving picture file in LP mode, and if they like it, they can take the time to download it to view it in better picture quality. |
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Other notes | |
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It is recommended that modems with a transmission speed of more than 33.6Kbps be used for streaming playback of moving pictures, since 28.8Kbps modems do not guarantee transmission speeds of 28.8Kbps. | |
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It is recommended that your Web site include a note stating that playback of moving pictures requires Windows® Media Player. Also, when sending e-mails with ASF file attachments, it is recommended to notify the addressee that Windows® Media Player is required to play back the attached files. | |
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Embedding playback of moving pictures prompts Windows® Media Player to start up within the browser instead of launching independently. It is reported, however, that moving pictures cannot be played back smoothly on some browsers or with certain preference settings. Consequently, embedding playback is not recommended at this time. | |
| Click here if your computer is not able to play back moving picture files. |
| Main Features / Specifications / Sample Clips / FAQ |
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