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diff --git a/kioslave/http/shoutcast-icecast.txt b/kioslave/http/shoutcast-icecast.txt deleted file mode 100644 index f7bdcf1e7..000000000 --- a/kioslave/http/shoutcast-icecast.txt +++ /dev/null @@ -1,605 +0,0 @@ - -Audio and Apache HTTPD -ApacheCon 2001 -Santa Clara, US - -April 6th, 2001 - -Sander van Zoest <sander@vanZoest.com> -Covalent Technologies, Inc. -<http://www.covalent.net/> - -Latest version can be found at: - <http://www.vanZoest.com/sander/apachecon/2001/> - -Introduction: - -About this paper: - -Contents: - - 1. Why serve Audio on the Net? - - This is almost like asking, why are you reading this? it might be - because of the excitement caused by the new media that has recently - crazed upon the internet. People are looking to bring their lifes onto - the net, one of the things that brings that closer to a reality is the - ability to hear live broadcasts of the worlds news, favorite sport; - hear music and to teleconference with others. Sometimes it is simply - to enhance the mood to a web site or to provide audio feedback of - actions performed by the visitor of the web site. - - 2. What makes delivering audio so different? - - The biggest reason to what makes audio different then traditional - web media such as graphics, text and HTML is the fact that timing - is very important. This caused by the significant increase in size - of the media and the different quality levels that exist. - - There really are two kinds of goals behind audio streams. - In one case there is a need for immediate response the moment - playback is requested and this can sacrifice quality. While - in the other case quality and a non-interrupted stream are much - more important. - - This sort of timing is not really required of any other media, - with the exception of video. In the case of HTML and images the - files sizes are usually a lot smaller which causes the objects - to load much quicker and usually are not very useful without - having the entire file. In audio the middle of a stream can have - useful information and still set a particular mood. - - 3. Different ways of delivery Audio on the Net. - Embedding audio in your Web Page - - This used to be a lot more common in the past. Just like embedding - an image in a web page, it is possible to add a sound clip or score - to the web page. - - The linked in audio files are usually short and of low quality to - avoid a long delay for downloading the rest of the web page and the - audio format needs to be supported by the browser natively or with - a browser plug-in to avoid annoying the visitor. - - This can be accomplished using the HTML 4.0 [HTML4] object element which - works similar to how to specify an applet with the object element. - In the past this could also be accomplished using the embed and bgsound - browser specific additions to HTML. - - example: - <object type="audio/x-midi" data="../media/sound.mid" width="200" height="26"> - <param name="src" value="../media/sound.mid"> - <param name="autostart" value="true"> - <param name="controls" value="ControlPanel"> - </object> - - Each param element is specific to each browser. Please check with each - browser for specific information in regards to what param elements are - available. - - In this method of delivering audio the audio file is served up via the - web server. When using an Apache HTTPD server make sure that the appropriate - mime type is configured for the audio file and that the audio file is - named and referenced by the appropriate extension. - - Although the current HTML 4.01 [HTML4] says to use the object element - many browsers out on the market today still look for the embed element. - Below find a little snipbit that will work work in many browsers. - - <object type="audio/x-midi" data="../media/sound.mid" width="200" height="26"> - <param name="src" value="../media/sound.mid"> - <param name="autostart" value="true"> - <param name="controls" value="ControlPanel"> - - <embed type="audio/x-midi" src="../media/sound.mid" - width="200" height="26" autoplay="true" controls="ControlPanel"> - <noembed>Your browser does not support embedded WAV files.</noembed> - </object> - - With the increasing installation base of the Flash browser plug-in by - Macromedia most developers that are looking to provide this kind of - functionality to a web page are creating flash elements that have their - own way of adding audio that is discussed in Flash specific documents. - - Downloading via HTTP - - Using this method the visitor to the website will have to download the - entire audio file and save it to the hard drive before it can be - listened to. (1) This is very popular with people that want to listen - to high quality streams of audio and have a below ISDN connection to - the internet. In some cases where the demand for a stream is high or - the internet is congested downloading the content even for high bandwidth - users can be affective and useful. - - One of the advantages of downloading audio to the local computer hard - drive is that it can be played back (once downloaded) any time as long - as the audio file is accessable from the computer. - - There are a lot of sites on the internet that provide this functionality - for music and other audio files. It is also one of the easiest ways to - delivery high quality audio to visitors. - - (1) Microsoft Windows Media Player in conjunction with the Microsoft - Internet Explorer Browser will automaticly start playing the - audio stream after a sufficient amount of the file has been - downloaded. This can be accomplished because of the tight - integration of the Browser and Media Player. With most audio players - you can listen to a file being downloaded, but you will have to - envoke the action manually. - - . On-Demand streaming via HTTP - - The real difference between downloading and on-demand streaming is - that in on-demand streaming the audio starts playing before the entire - audio file has been downloaded. This is accomplished by a hand of off - the browser to the audio player via an intermediate file format that - has been configured by the browser to be handled by the audio player. - - Look in a further section entitled "Linking to Audio via Apache HTTPD" - below for more information about the different intermediate file formats. - - This type of streaming is very popular among the open source crowd and - is the most widely implemented using the MP3 file format. Apache, - Shoutcast [SHOUTCAST] and Icecast [ICECAST] are the most common - software components used to provide on-demand streaming via HTTP. Both - Icecast and Shoutcast are not fully HTTP compliant, but Icecast is - becoming closer. For more information about the Shoutcast and Icecast - differences see the section below. - - Sites like Live365.com and MP3.com are huge sites that rely on this - method of delivery of audio. - - . On-Demand Streaming via RTSP/RTP - - RTSP/RTP is a new set of streaming protocols that is getting more - backing and becoming more popular by the second. The specification - was developed by the Internet Engineering Task Force Working Groups - AVT [IETFAVT] and MMUSIC [IETFMMUSIC]. RTP the Realtime Transfer - Protocol has been around longer then RTSP and originally came out - of the work towards a better teleconferencing, mbone, type system. - RTSP is the Real-Time Streaming Protocol that is used as a control - protocol and acts similarily to HTTP except that it maintains state - and is bi-directional. - - Currently the latest Real Networks Streaming Servers support RTSP - and RTP and Real Networks own proprietary transfer protocol RDT. - Apple's Darwin Streaming server is also RTSP/RTP compliant. - - The RTSP/RTP protocol suite is very powerful and flexable in regards - to your streaming needs. It has the ability to suport "server-push" - style stream redirects and has the ability to throttle streams to - ensure the stream can sustain the limited bandwidth over the network. - - For On-Demand streams the RTP protocol would usually stream over - TCP and have a second TCP connection open for RTSP. Because of the - rich features provided by the protocol suite, it is not very well - suited to allow people to download the stream and therefore the - download via HTTP method might still be preferred by some. - - . Live Broadcast Streaming via RTSP/RTP - - In the case of a live broadcast streaming RTSP/RTP shines. RTP allowing - for UDP datagrams to be transmitted to clients allows for fast immediate - delivery of content with the sacrifice of reliability. The RTP stream - can be send over IP Multicast to minimize bandwidth on the network. - - Many Content Delivery Networks (CDNs) are starting to provide support for - RTSP/RTP proxies that should provide a better quality streaming environment - on the internet. - - Much work is also being done in the RTP space to provide transfers over - telecommunication networks such as cellular phones. Although not directly - related, per se, it does provide a positive feeling knowing that all the - audio related transfer groups seem to be working towards a common standard - such as RTP. - - . On-Demand or Live Broadcast streaming via MMS. - - This is the Microsoft Windows Media Technologies Streaming protocol. It - is only supported by Microsoft Windows Media Player and currently only - works on Microsoft Windows. - - 5. Configuring Mime Types - - One of the most hardest things in serving audio has been the wide variety - of audio codecs and mime types available. The battle of mime types on the - audio player side of things isn't over, but it seems to be a little more - controlled. - - On the server side of things provide the appropriate mime type for the - particular audio streams and/or files that are being served to the audio - players. Although some clients and operating systems handle files fully - based on the file extension. The mime type [RFC2045] is more specific - and more defined. - - The registered mime types are maintained by IANA [IANA]. On their site - they have a list of all the registered mime types and their name space. - - If you are planning on using a mime type that isn't registered by IANA - then signal this in the name space by adding a "x-" before the subtype. - Because this was not done very often in the audio space, there was a - lot of confusion to what the real mime type should be. - - For example the MPEG 1.0 Layer 3 Audio (MP3) [ORAMP3BOOK] mime type - was not specified for the longest time. Because of this the mime type - was audio/x-mpeg. Although none of the audio players understood - audio/x-mpeg, but understood audio/mpeg it was not a technically - correct mime type. Later audio players recognized this and started - using the audio/x-mpeg mime type. Which in the end caused a lot - of hassles with clients needing to be configured differently depending - on the website and client that was used. Last november we thanked - Martin Nilsson of the ID3 tagging project for registering audo/mpeg - with IANA. [RFC3003] - - Correct configuration of Mime Types is very important. Apache HTTPD - ships with a fairly up to date copy of the mime.types file, so most - of the default ones (including audio/mpeg) are there. - - But in case you run into some that are not defined use the mod_mime - directives such as AddType to fix this. - - Examples: - AddType audio/x-mpegurl .m3u - AddType audio/x-scpls .pls - AddType application/x-ogg .ogg - - - 6. Common Audio File Formats - - There are many audio formats and metadata formats that exist. Many of - them do not have registered mime types and are hardly documented. - This section is an attempt at providing the most accurate mime type - information for each format with a rough description of what the files - are used for. - - . Real Audio - - Real Networks Proprietary audio format and meta formats. This is one - of the more common streaming audio formats today. It comes in several - sub flavors such as Real 5.0, Real G2 and Real 8.0 etc. The file size - varies depending on the bitrates and what combination of bitrates are - contained within the single file. - The following mime types are used - audio/x-pn-realaudio .ra, .ram, .rm - audio/x-pn-realaudio-plugin .rpm - application/x-pn-realmedia - - . MPEG 1.0 Layer 3 Audio (MP3) - - This is currently one of the most popular downloaded audio formats - that was originally developed by the Motion Pictures Experts Group - and has patents by the Fraunhofer IIS Institute and Thompson - Multimedia. [ORAMP3BOOK] The file is a lossy compression that at - a bitrate of 128kbps reduces the file size to roughly a MB/minute. - The mime type is audio/mpeg with the extension of .mp3 [RFC3003] - - . Windows Media Audio - - Originally known as MS Audio was developed by Microsoft as the MP3 - killer. Still relatively a new format but heavily marketed by - Microsoft and becoming more popular by the minute. It is a successor - to the Microsoft Audio Streaming Format (ASF). - - . WAV - - Windows Audio Format is a pretty semi-complicated encapsulating - format that in the most common case is PCM with a WAV header up front. - It has the mime type audio/x-wav with the extension .wav. - - . Vorbis - - Ogg Vorbis [VORBIS] is still a relatively new format brought to - life by CD Paranoia author Christopher Montgomery; known to the - world as Monty. It is an open source audio format free of patents - and gotchas. It is a codec/file format that is roughly as good as - the MP3 format, if not much better. The mime type for Ogg Vorbis is - application/x-ogg with the extension of .ogg. - - . MIDI - - The MIDI standard and file format [MIDISPEC] have been used by - Musicians for a long time. It is a great format to add music to - a website without the long download times and needing special players - or plug-ins. The mime type is audio/x-midi and the extension is .mid - - . Shockwave Flash (ADPCM/MP3) [FLASH4AUDIO] - - Macromedia Flash [FLASH4AUDIO] uses its own internal audio format - that is often used on Flash websites. It is based on Adaptive - Differential Pulse Code Modulation (ADPCM) and the MP3 file format. - Because it is usually used from within Flash it usually isn't served - up seperatedly but it's extension is .swf - - There are many many many more audio codecs and file formats that exist. - I have listed a few that won't be discussed but should be kept in mind. - Formats such as PCM/Raw Audio (audio/basic), MOD, MIDI (audio/x-midi), - QDesign (used by Quicktime), Beatnik, Sun's AU, Apple/SGI's AIFF, AAC - by the MPEG Group, Liquid Audio and AT&T's a2b (AAC derivatives), - Dolby AC-3, Yamaha's TwinVQ (originally by Nippon Telephone and Telegraph) - and MPEG-4 audio. - - 7. Linking to Audio via Apache HTTPD - - There are many different ways to link to audio from the Apache HTTPD - web server. It seems as if every codec has their own metafile format. - The metafile format is provided to allow the browser to hand off the - job of requesting the audio file to the audio player, because it is - more familiar with the file format and how to handle streaming or how - to actually connect to the audio server then the web browser is. - - This section will discuss the more common methods to provide streaming - links to provide that gateway from the web to the audio world. - - Probably the one that is the most recognized file is the RAM file. - - . RAM - - Real Audio Metafile. It is a pretty straight forward way that Real - Networks allowed their Real Player to take more control over their - proprietary audio streams. The file format is simply a URL on each - line that will be streamed in order by the client. The mime type - is the same as other RealAudio files audio/x-pn-realaudio where - the pn stands for Progressive Networks the old name of the company. - - . M3U - - This next one is the MPEG Layer 3 URL Metafile that has been around - for a very long time as a playlist format for MP3 players. It supported - URLs pretty early on by some players and got the mime type - audio/x-mpegurl and is now used by Icecast and many destination sites - such as MP3.com. The format is exactly the same as that of the RAM - file, just a list of urls that are separated by line feeds. - - . PLS - - This is the playlist files used by Nullsoft's Winamp MP3 Player. Later - on it got more widely used by Nullsoft's Shoutcast and has the mime - type of audio/x-scpls with the extension .pls. Before shoutcast the - mimetype was simply audio/x-pls. As you can see in the example below - it looks very much like a standard windows INI file format. - - Example: - [playlist] - numberofentries=2 - File1=<uri> - Title1=<title> - Length1=<length or -1> - File2=<uri> - Title2=<title> - Length2=<length or -1> - - . SDP - - This is the Session Description Protocol [RFC2327] which is heavily - used within RTSP and is a standard way of describing how to subscribe - to a particular RTP stream. The mime type is application/sdp with the - extension .sdp . - - Sometimes you might see RTSL (Real-Time Streaming Language) floating - around. This was an old Real Networks format that has been succeeded - by SDP. It's mimetype was application/x-rtsl with the extension of .rtsl - - . ASX - - Is a Windows Media Metafile format [MSASX] that is based on early XML - standards. It can be found with many extensions such as .wvx, .wax - and .asx. I am not aware of a mime type for this format. - - . SMIL - - Is the Synchronized Multimedia Integration Language [SMIL20] that - is now a W3C Recommendation [W3SYMM]. It was originally developed - by Real Networks to provide an HTML-like language to their Real Player - that was more focused on multimedia. The mime type is application/smil - with the extensions of either .smil or .smi - - . MHEG - - Is a hypertext language developed by the ISO group. [MHEG1] [MHEG5] - and [MHEG5COR]. It has been adopted by the Digital Audio Visual - Council [DAVIC]. It is more used for teleconferencing, broadcasting - and television, but close enough related that it receives a mention - here. The mime type is application/x-mheg with the extension of - .mheg - - 8. Configuring Apache HTTPD specificly to serve large Audio Files - - Some of the most common things that you will need to adjust to be - able to serve many large audio files via the Apache HTTPD Server. - Because of the difference in size between HTML files and Audio files, - the MaxClients will need to be adjusted appropriatedly depending on - the amount of time listeners end up tieing up a process. If you are - serving high quality MP3 files at 128kbps for example you should - expect more then 5 minute download times for most people. - - This will significantly impact your webserver since this means that - that process is occupied for the entire time. Because of this you - will also want to in crease the TimeOut Directive to a higher - number. This is to ensure that connections do not get disconnected - half way through a transfer and having that person hit "reload" - and connect again. - - Because of the amount of time the downloads tie up the processes - of the server, the smallest footprint of the server in memory would - be recommended because that would mean you could run more processes - on the machine. - - After that normal performance tweaks such as max file descriptor - changes and longer tcp listen queues apply. - - 9. Icecast/Shoutcast Protocol. - - Both protocols are very tightly based on HTTP/1.0. The main difference - is a group of new headers such as the icy headers by Shoutcast and the - new x-audiocast headers provided by Icecast. - - A typical shoutcast request from the client. - - GET / HTTP/1.0 - - ICY 200 OK - icy-notice1:<BR>This stream requires <a href="http://www.winamp.com/"> - Winamp</a><BR> - icy-notice2:SHOUTcast Distributed Network Audio Server/posix v1.0b<BR> - icy-name: Great Songs - icy-genre: Jazz - icy-url: http://shout.serv.dom/ - icy-pub: 1 - icy-br: 24 - - <data><songtitle><data> - - The icy headers display the song title and other formation including if - this stream is public and what the bitrate is. - - A typical icecast request from the client. - - GET / HTTP/1.0 - Host: icecast.serv.dom - x-audiocast-udpport: 6000 - Icy-MetaData: 0 - Accept: */* - - HTTP/1.0 200 OK - Server: Icecast/VERSION - Content-Type: audio/mpeg - x-audiocast-name: Great Songs - x-audiocast-genre: Jazz - x-audiocast-url: http://icecast.serv.dom/ - x-audiocast-streamid: - x-audiocast-public: 0 - x-audiocast-bitrate: 24 - x-audiocast-description: served by Icecast - - <data> - - NOTE: I am mixing the headers of the controlling client with those form - a listening client. This might be better explained at a latter - date. - - The CPAN Perl Package Apache::MP3 by Lincoln Stein implements a little of - each which works because MP3 players tend to support both. - - One of the big differences in implementations between the listening clients - is that Icecast uses an out of band UDP channel to update metadata - while the Shoutcast server gets it meta data from the client embedded within - the MP3 stream. The general meta data for the stream is set up via the - icy and x-audiocast HTTP headers. - - Although the MP3 standard documents were written for interrupted communication - it is not very specific on that. So although it doesn't state that there is - anything wrong with embedding garbage between MPEG frames the players that - do not understand it might make a noisy bleep and chirps because of it. - -References and Further Reading: - -[DAVIC] - Digital Audio Visual Council - <http://www.davic.org/> - -[FLASH4AUDIO] - L. J. Lotus, "Flash 4: Audio Options", ZD, Inc. 2000. - <http://www.zdnet.com/devhead/stories/articles/0,4413,2580376,00.html> - -[HTML4] - D. Ragget, A. Le Hors, I. Jacobs, "HTML 4.01 Specification", W3C - Recommendation, December, 1999. - <http://www.w3.org/TR/html401/> - -[IANA] - Internet Assigned Numbers Authority. - <http:/www.iana.org/> - -[ICECAST] - Icecast Open Source Streaming Audio System. - <http://www.icecast.org/> - -[IETFAVT] - Audio/Video Transport WG, Internet Engineering Task Force. - <http://www.ietf.org/html.charters/avt-charter.html> - -[IETFMMUSIC] - Multiparty Multimedia Session Control WG, Internet Engineering Task - Force. <http://www.ietf.org/html.charters/mmusic-charter.html> - -[IETFSIP] - Session Initiation Protocol WG, Internet Engineering Task Force. - <http://www.ietf.org/html.charters/sip-charter.html> - -[IPMULTICAST] - Transmit information to a group of recipients via a single transmission - by the source, in contrast to unicast. - IP Multicast Initiative - <http://www.ipmulticast.com/> - -[MIDISPEC] - The International MIDI Association,"MIDI File Format Spec 1.1", - <http://www.vanZoest.com/sander/apachecon/2001/midispec.html> - -[MHEG1] - ISO/IEC, "Information Technology - Coding of Multimedia and Hypermedia - Information - Part 1: MHEG Object Representation, Base Notation (ASN.1)"; - Draft International Standard ISO 13522-1;1997; - <http://www.ansi.org/> - <http://www.iso.ch/cate/d22153.html> - -[MHEG5] - ISO/IEC, "Information Technology - Coding of Multimedia and Hypermedia - Information - Part 5: Support for Base-Level Interactive Applications"; - Draft International Standard ISO 13522-5:1997; - <http://www.ansi.org/> - <http://www.iso.ch/cate/d26876.html> - -[MHEG5COR] - Information Technology - Coding of Multimedia and Hypermedia Information - - Part 5: Support for base-level interactive applications - - - Technical Corrigendum 1; ISO/IEC 13552-5:1997/Cor.1:1999(E) - <http://www.ansi.org/> - <http://www.iso.ch/cate/d31582.html> - -[MSASX] - Microsoft Corp. "All About Windows Media Metafiles". October 2000. - <http://msdn.microsoft.com/workshop/imedia/windowsmedia/ - crcontent/asx.asp> - -[ORAMP3] - S. Hacker; MP3: The Definitive Guide; O'Reilly and Associates, Inc. - March, 2000. - <http://www.oreilly.com/catalog/mp3/> -[RFC2045] - N. Freed and N. Borenstein, "Multipurpose Internet Mail - Extensions (MIME) Part One: Format of Internet Message Bodies", - RFC 2045, November 1996. <http://www.ietf.org/rfc/2045.txt> - -[RFC2327] - M. Handley and V. Jacobson, "SDP: Session Description Protocol", - RFC 2327, April 1998. <http://www.ietf.org/rfc/rfc2327.txt> - -[RFC3003] - M. Nilsson, "The audio/mpeg Media Type", RFC 3003, November 2000. - <http://www.ietf.org/rfc/rfc3003.txt> - -[SHOUTCAST] - Nullsoft Shoutcast MP3 Streaming Technology. - <http://www.shoutcast.com/> - -[SMIL20] - L. Rutledge, J. van Ossenbruggen, L. Hardman, D. Bulterman, - "Anticipating SMIL 2.0: The Developing Cooperative Infrastructure - for Multimedia on the Web"; 8th International WWW Conference, - Proc. May, 1999. - <http://www8.org/w8-papers/3c-hypermedia-video/anticipating/ - anticipating.html> - -[W39CIR] - V. Krishnan and S. G. Chang, "Customized Internet Radio"; 9th - International WWW Conference Proc. May 2000. - <http://www9.org/w9cdrom/353/353.html> - -[VORBIS] - Ogg Vorbis - Open Source Audio Codec - <http://www.xiph.org/ogg/vorbis/> - -[W3SYMM] - W3C Synchronized Multimedia Activity (SYMM Working Group); - <http://www.w3.org/AudioVideo/> |