Stream Music In PHP

Various residents host their own music for the parcel. Quite often, this is just a big MP3 file. The issues of hosting such big MP3 are, that the viewer will download the file 'as-is'. While this is no issue for short files (a few megabyte), it is when the podcast is several hours in length.
To be able to stream my own parcel music, without the use of (commercial/difficult to setup/) streamers like icecast, i written a simple PHP script that streams a huge mp3 file. It performs some extra tricks to make the listening experience glitch-free for SL viewers. This very script has been tested for quite a while, and it does just what it needs to do: host hassle free music for my parcel.
You will need to prepare your own podcast / mp3 stream, as a single file. This script will not serve a playlist, it will just endlessly loop a big MP3 file, whilst synchronizing listeners. Make sure you have appropiate bandwith. Also, usage is only recommended for the more experienced web server admins, if you do not know what 'LAMP' means, have no scripting experience, or have no root access to the server you are hosting this on (in case of a malfunction), please refrain from using this code.
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 <?
 //GPL3
 
 //MP3 STREAMING FROM PHP
 //This script streams a big MP3 file at an appropiate speed
 //Also, it will synchronize several listeners to the same position in the mp3
 
 //Quick usage: Edit the 3 variables below in the 'settings' section, host this script together with a big MP3 on a lamp server.
 
 //This script was optimized for Second Life music streaming, issues dodged:
 //* The mp3 is actively streamed, instead of sent as a whole file at once
 //* Listeners are synchronized, so they actually will hear the same song whilst being on the same parcel
 //* MP3 is nicely (instead of arbitrary) split in chunks to dodge 'skipping' errors that SL viewers tend to behave
 //* Insignificant server load(** up to a reasonable amount of viewers, say, <20)
 //* Tested for over a year for proper functioning without raising issues
 
 //Limitations
 //Requires an MPEG1 LAYER III file as input (the most common MP3 format)
 //Assumes a single big file (podcast). This script was not made to stream a playlist.
 //The file should be properly encoded to avoid issues with the SL player:
 //* VBR _might_ work but is not recommended due to the viewers' real-time broadcast skipping
 //* If the encoder supports 'bit buckets' - make sure they are disabled as they are incompatible with SL's player(**)
 //(**) When streaming 'live' - SL player seems to understand if the whole file was downloaded instead of streamed.
 //The resolution of the synchronisation is not precise, though generally <1 second. As listeners join, slight offsets might accumulate
 //This script is ment as example how to stream using proper timekeeping and chunking.
 //It is missing features as streaming multiple files from a directory, though such behaviour is easily customized.
 
 //Feature, not bug
 //With zero listeners, the stream will not progress, instead it'll 'wait' at current position untill at least 1 listener joins
 
 //Issues:
 //If the mp3 exists but has zero length, the script may end in an endless loop eating 100% cpu time. please fix.
 
 //Requirements:
 //LAP(Linux, Apache, PHP) configuration
 //(WAP(Windows) may work but untested, potentional issues revolve around microtime(), fastcgi and locked temporary files).
 //PHP configuration that allows overriding script run time to infinite
 //Writeable TMP directory
 //Properly created MP3 stream (podcast), preferably several hours in length:
 // * Simply concatting files may work for testing but is not recommended and may lead to audible glitches
 // * The prefered way is to either: stream your playlist with an audio player like winamp, then output the stream as .mp3
 // * Or use an editor (like audacity) to create your podcast, output as single file
 // * Any other means or software to create a podcast
 //The intention of this script is to generate a glitch-free audio experience, using no more bandwidth than required
 
 //CHANGE HISTORY
 //0.01 - initial version
 //0.02 - removed dependancy from external mp3 header library. please set bitrate manually. auto-detect wasn't reliable anyways
 //0.03 - documented some more and cleaned up code a tiny bit. might release it as GPL
 
 
 //settings, please fill this variables with your own
 $mp3="bigstreamfile.mp3";
 $bitrate=128;
 
 //adjust for your system. use a unique lock file for each mp3 you serve.
 //$tmp="/tmp/${mp3}.posinfo";
 $tmp="/tmp/stream1pos"; 
 
 //Enable debug to get textual output in a browser. The stream is not listenable with debug enabled.
 $debug=0; //false; //true;
 
 //disable error reporting if you like
 error_reporting (E_ALL);
 
 
 // NO EDITING REQUIRED BELOW THIS LINE, EDIT AT OWN RESPONSABILITY //
 
 //SUPPORT FUNCTIONS
 function writePos() {
 global $h, $timekeeper;
 $fff=fopen ($tmp, "w");
 fputs ($fff, "".ftell ($h)."\n");
 fputs ($fff, $timekeeper."\n");
 fclose ($fff);
 }
 
 //global $buffcache;
 
 function sendBuff($bff) {
 print $bff;
 flush();
 return;
 }
 
 function readBuffs($fh) {
 $b="";
 for ($i = 0; $i<22; $i++) {
 $b.=readBuff($fh);
 } 
 return $b;
 }
 
 function readBuff($fh) {
 global $framesize;
 //read from file untill we receive a $FF marker
 $m="";
 do {
 $m=fread($fh, 4);
 if (feof($fh))
 return "";
 //requiring mpeg1 layer 3. Adjust for other containers / chunkmarkers / right here
 } while (($m[0]!=chr(255)) || !(($m[1]==chr(250)) || ($m[1]==chr(251))) );
 $bl=$framesize-4;
 if (ord($m[2]) & 2) //padding
 $bl++;
 $m.=fread ($fh, $bl);
 return $m;
 }
 
 
 //`main()`
 
 $file=$mp3;
 if (!file_exists($file))
 die();
 $framesize=floor (144000.0 * $bitrate / 44100);
 $blocksize=16384;
 $playspeed=1000.0 * $bitrate / 8.0;
 $sleeptime = (1.0 * $blocksize / ($playspeed));
 
 if ($debug)
 header ("Content-Type: text/plain");
 else {
 header ("Content-Type: audio/mpeg");
 header ("Content-Transfer-Encoding: binary");
 header ("Pragma: no-cache");
 header ("icy-br: ".$bitrate);
 }
 
 //request unlimited runtime
 set_time_limit(0);
 if ($debug)
 print ("framesize: ".$framesize);
 
 $h=fopen($file, "rb");
 
 if (file_exists ($tmp)) {
 //read our position from file.
 $ff=fopen ($tmp, "r");
 $position=fgets($ff);
 $postime=fgets($ff);
 fclose ($ff);
 }
 
 //increase position by elapsed time for syncing listeners.
 if ($postime) {
 $elapsed = microtime(true)-$postime;
 //we force to float to bypass a 32 bit integer limit
 //looping for multiple days if needed (its not an issue)
 $position += 1.0 * $elapsed * ($bitrate / 8);
 $fs=filesize($file);
 while ($position>$fs) {
 $position-=$fs;
 }
 }
 fseek ($h, $position);
 //send a reasonable buffer to start
 for ($j=0; $j<3; $j++) {
 $buff=readBuffs($h).readBuffs($h).readBuffs($h);
 print $buff;
 }
 
 $buff=readBuffs($h);
 $timekeeper=microtime(true);
 $counter=0;
 
 //main loop:
 while (($buff!="") && !connection_aborted()) {
 if ($debug) {
 echo "Buff size: ".strlen($buff)." first chars: ".ord($buff[0])." ".ord($buff[1])." ".ord($buff[2])." ".ord($buff[3])." file pointer ".ftell($h)."\n";
 } else
 echo ($buff);
 flush();
 $counter++;
 if (!($counter%30))
 writePos();
 $bwl=strlen($buff);
 $buff=readBuffs($h);
 if ($buff=="") {
 fseek ($h, 0);
 $buff=readBuff($h);
 }
 $timekeeper=$timekeeper+1.0*$bwl/$playspeed;
 time_sleep_until($timekeeper); 
 }
 
 writePos();
 fclose($h);
 
 ?>
--Tano Toll 06:05, 15 October 2011 (PDT)