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Thread: Meta-files: ram, smil, asx, wax, wvx, m3u

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  1. #1
    dBpoweramp Guru ChristinaS's Avatar
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    Apr 2004
    Montreal, Canada

    Arrow Meta-files: ram, smil, asx, wax, wvx, m3u

    I see the questions involving converting files with extensions such as .ram, .smil, .asx, .wax, .wvx, .m3u, etc keep coming back in various forms.

    Here is where I would like to contribute what little I know of such files and how to handle them. Mine is more of a layman's explanation of these concepts rather than a rigorously technical one.

    These are all meta-files. They are not audio or video files, but rather text files used for two inter-related purposes:
    1) creating playlists for particular types of actual audio/video files
    2) allowing pseudo-streaming of those particular types of actual audio/video files

    I use the term pseudo-streaming to differentiate from actual streaming which will only be achieved by a streaming server, which is not the case for most servers on the net.

    So when you encounter a file with one of those extensions, the first thing you should do is open it with Notepad. Unless somebody has mis-labelled them (in error or intentionally), you should be able to read the contents of the file and you will find reference to the actual audio/video file(s).

    Then you identify the actual media file name referenced in the meta-file, and this is the file you need to download and work with for purposes of conversion.

    These meta-files have different layouts, but essentially they all accomplish the same thing: ultimately point to the actual media files to be streamed.

    I will explain all these different types of meta-files briefly.

    1. .m3u - the meta file for .mp3 audio files and for .mpg video files
    This is the simplest meta-file. It contains just the names of each individual mp3 or mpg file, one per line, with no special characters or tags. The audio/video files will be streamed or played in sequence, by whatever your default player is for those media types. For me, it is usually Windows Media Player, bit it could as well be Real Player or Quicktime or any other that has set itself as the default player on your pc.
    2. .wax - the meta file specifically for .wma audio files
    .wma is the native format of compressed windows audio media.
    Windows Media Player plays such files, but other players can play them as well.
    The layout of a .wax file is something like this:
    <ASX VERSION="3.0"> 
      <REF HREF="http://www.my_site.com/xyz.wma" />
      <Abstract>blah, blah</Abstract>
      <Author>blah, blah</Author>
      <Copyright>blah, blah</Copyright>
      <REF HREF="http://www.my_site.com/abc.wma" />
      <Abstract>blah, blah</Abstract>
      <Author>blah, blah</Author>
      <Copyright>blah, blah</Copyright>
    You can clearly see the names of the underlying .wma audio files in the <REF HREF..> tags. The other tags like <title>, <author>, <copyright> are optional, self-explanatory, but their purpose is to add extra information to what is displayed by the player when the file is being played.

    For each audio file there will be a separate grouping like what you see between the <ENTRY>...</ENTRY> tags.

    The different audio files will be played in the sequence that they appear.

    There are other tags that can appear in the .wax file, but these given here are the most common.

    In addition to .wma, audio files types can be anything else that Windows media player understands: .asf, .mp3, .wav, .mid, etc. The list is quite long, but you get the picture.
    3. .wvx - the meta file specifically for .wmv video files
    .wmv is the native format of compressed windows video media.

    The layout is exactly the same as for the .wax meta-file, except that the media file names being referenced in the <REF HRF..> tags have the extension .wmv.

    You may find other video file extensions in the <REF HREF...> tags as well: .mpg, .avi, etc. Again, it's any video type that Window Media Player can understand and play.
    4. .asx - the meta file specifically for both .wma audio files and .wmv video files.

    Again, this meta-file has the same layout as .wax and .wvx.

    You guessed it, the .asx file can be used for either audio or video media files, so the extensions used in the <REF HREF...> tags can be either.

    So all the different types of file extensions can be used in an .asx file, for both audio and video files, whatever Windows Media Player can understand and play.

    Your different entries can alternate between any kind of audio file to any kind of video file.
    5. .ram - the simple meta file specifically for Real Media, the audio & video files that are native to Real Player.
    The Real Media file extensions are usually .rm for both audio and video files. There may appear a third character in the .rm file extension, but this is just further refinement.

    As they are proprietary to Real Networks, usually these file types have to be played through one of their players. I said usually, because in particular dAP has been designed to incorporate the Real Media audio codecs as well. I don't know at this point if the Real Media video can be played through dAP.

    The layout of a .ram meta-file is very simple, one line for each .rm file that is to be played, exactly as the layout of the .m3u files given above.

    No other information is given in the .ram file, perhaps because the .rm files can have their own internal information that will be displayed by the Real Player as the file is being played.

    6. .smi and .smil - a special file for many media types.

    This is not technically speaking a meta file, but the purpose is similar.

    SMIL (pronounced smile) stands for Synchronized Multimedia Integration Language. It is a markup language (like HTML) and is designed to be easy to learn and deploy on Web sites. SMIL was created specifically to solve the problems of coordinating the display of a variety of media (multimedia) on Web sites. By using a single time line for all of the media on a page their display can be properly time coordinated and synchronized.

    You will most often see it in relation to Real Media files though, so I will only explain a simple layout of a .smil file in that context:

          <!-- Presentation attributes. -->
    	<meta name="author" content="www.my-site.com"/>
    	<meta name="title" content="my media file"/>
    	<meta name="copyright" content=" 2004"/>
    <audio src="http://www.my-site.com/my-music/my-song-1.rm" />
    <video src="http://www.my-site.com/my-music/my-video-1.rm" />
    The portion appearing in the <head> .... </head> section is basically descriptive. The portion appearing in the <body> ... </body> section is what gives the names of the media files that will be played.
    There are many more snippets of information that can be added to each and every meta-file type I have described here. I don't know them all myself. The world of media players as the web itself are constantly evolving and new refinements are added all the time.

    One other important piece of information is relative to streaming servers. In particular how addressing files on them is done. This is quite complex, but in general you can say that if the media file is prefixed by http:// or nothing in particular, then we are not dealing with a streaming server as such. The media file will be downloadable from that address by some means. For instance you copy the full address of the file name and paste it in the browser's address bar and you can access the media file directly. Then you usually can save it to your hard disk from the options available in your player.

    If you see something less common like mms:// in front of a file name, then you are dealing with a streaming server and most likely you cannot save the media file directly to disk. In that case you will have to use dMC Auxiliary Input to play the meta file and capture the audio (best to capture to .wav), before you convert to anything.

    I would kindly urge anybody who finds factual errors or discrepancies or something useful that can be added to clarify this mini-tutorial to please send me a private message and refer to this thread.
    Last edited by ChristinaS; 06-04-2004 at 10:06 AM.

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