• Streaming Audio Primer (Part 5)

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    11/28/2011 /  Articles

    Updating Your Web Page
    If you have come this far, then you have accomplished the most difficult part. If you already have your own web page, then you have probably done this next step: putting the file on the Internet. To do this simply upload the audio file to your web page and provide an appropriate link for someone to download the file. You might encapsulate your files into a ZIP archive, since it is much easier to download ZIP files in some browsers. Shareware versions programs that create ZIP archives are available, such as WinZIP. However, the pseudo-streaming techniques will not work with ZIPped files. They must be posted as *.MP3 or *.VQF. The last key is the *.M3U and *.VQL files which point to the actual MP3 or VQF files, which will be discussed in more detail below.

    If you want to do this right, I would suggest making a separate page just for these downloads. On this page you should include links for people downloading shareware versions of players that will play either the MP3 or VQF files. I would suggest the Microsoft Windows Media Player or the Adobe Flash Player . The Microsoft Media Player will probably become the most widely player, while sonique is a much more aesthetically pleasing and functional player. One of these functions include the unique ability to both play a stream and save the file, all at the same time.

    The VQF player can be downloaded from Here. It is actually a browser plug-in; although, it can be operated without your browser.

    Pseudo-Streaming Audio
    Pseudo-Streaming Audio is a technique that lets someone listen to an audio file immediately without having to download the entire file. In this respect it is similar to Real Audio. Although this label is not technically correct because this technique does really stream audio, it is called pseudo-streaming to distinguish it from RealAudio’s dynamically compensated streaming, which is what many people think of as streaming.

    Streaming works by downloading the file as normal, but decoding and playing the file on the fly. As long as the file info is downloaded faster than it can be played, then the listener can detect no difference whatsoever between pseudo-streaming and dynamic streaming (Real Audio). This requires a modem connection to be greater than the bit rate which was set during encoding. However, if the listener has a slower connection, then their computer does not play until it has downloaded enough information to begin playing with a buffer to spare. This may result in some pauses during playing. But, the tests that I have run show that this never occurs with a 28.8 kbps modem if the stream’s bit rate is equal to or less than 20 kbps.

    Real Audio is different in that the files are posted on a special server that adjusts the audio quality (lower quality means less information must be transmitted) to accommodate slower connections. However, for a given rate, the MP3 and VQF sound much better than Real Audio! The true difference between Real Audio and MP3 streams is that a Real Audio file actually contains information for multiple bit rates. This redundancy makes the file huge; however, it allows a single file to support multiple connection speeds. This is the only true drawback to this MP3 pseudo-streaming technique – high bandwidth listeners must listen to the same quality as used by listeners with the slowest connection speeds. But, for voice and speech audio, a quality can be chosen that sounds pleasant at even low connection speeds.

    Both VQF and MP3 can accommodate pseudo-streaming. In both cases, the key to this magic is a small file called a “locator file”. This file contains nothing more than the http address of the audio file. However, this special locator file directs a listener’s player to the audio files location and instructs the media player to play the audio stream as it is downloading.

    All locator files for the MP3 format have the extension M3U. Files with this extension typically contain a “play-list” of files in a given location. If only a single file is included, then only that file will be played, but if multiple files are included, then the player will continue and play the additional “tracks” after the first one is completed. Using the “track seek” buttons, a listener can jump from one track to the next.

    Server Configuration?
    A good ISP server will probably have the server configured properly, but if you have any trouble, then you may have to contact your ISP provider or web-master. A typical problem with server configurations would be clicking on a link and a browser window popping up, filled with garbage text.

    The server configuration revolve around one issue – application association. Before a server directs ANY file to your computer through the web, it first tells your computer what kind of file it is and if any specific program should be used to open the file. For example, your server tells your computer that all files with extension HTML or HTM should be opened using your web-browser. A few low-budget ISP’s may not have configured their server to recognize files of extension MP3, M3U, VQF, etc.

    If you have trouble with either one, be sure to contact your ISP provider or webmaster. They may ask you to post an additional file labeled “.htaccess”. The period in front is important. (You could try posting this on your own.) This file tells the server how to handle files with specific extensions and whether or not to associate a browser plug-in or application with them. The file must be posted in the same directory, or higher, as the audio files. Any subdirectories within the same directory as the .htaccess file, will “inherit” the same settings. My .htaccess file looks like this:

    AddType application/octet-stream mp3
    AddType audio/x-mpegurl m3u
    AddType audio/x-twinvq vqf
    AddType audio/x-twinvq vql
    AddType audio/x-twinvq vqe

    The first line tells the server that files with the extension MP3 are applications that must be downloaded in binary form – they are not ASCII text or HTML code. The second line associates files with the extension M3U with the default audio player. The last 3 lines tell the browser that the files of those extensions are associated with file type “audio” and to use the plugin “twinvq” to play them.

    Although, you may not have to do this, I have included it for the few who may need it. Again, first ask your webmaster and ISP if you have any problems. It won’t hurt to add the above “.htaccess” file, even if the server doesn’t recognize it.

    Concluding Thoughts
    The bottom line is that the MP3/VQF setup is less complicated, less sophisticated, and less expensive. Moreover, it works almost as well as Real Audio; and for some performance parameters, it is even better, such as smaller file size for the same quality. The MP3 format is already extremely popular with those who trade and share music over the Internet, and its popularity is continuing to grow. Eventually, as modem speeds increase, formats like MP3 and VQf will topple the entire Real Audio regime because of the complexity of setting up Real Audio files, thereby removing the only advantage that Real Audio has over MP3 and VQF.

    Part 1: Introduction
    Part 2: Digital Recording
    Part 3: Reducing Noise
    Part 4: Encoding
    Part 5: Web Pages

     

    Posted by deliveryourmedia @ 6:33 pm

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