diff --git a/extract-playlist.php b/extract-playlist.php
new file mode 100644
index 0000000..982a64e
--- /dev/null
+++ b/extract-playlist.php
@@ -0,0 +1,264 @@
+<?php
+
+class MP4Reader {
+
+    /**
+     * @var resource $file
+     */
+    private $file;
+
+    /**
+     * @param string $filename
+     */
+    public function __construct( $filename ) {
+        $this->file = fopen( $filename, 'rb' );
+        if ( !$this->file ) {
+            throw new Exception( 'Failed to open MP4 input file' );
+        }
+    }
+
+    function __destruct() {
+        if ( $this->file ) {
+            fclose( $this->file );
+            $this->file = null;
+        }
+    }
+
+    /**
+     * @return int
+     */
+    public function pos() {
+        $pos = ftell( $this->file );
+        if ( $pos === false ) {
+            throw new Exception( 'Failed to read position in MP4 file' );
+        }
+        return $pos;
+    }
+
+    /**
+     * @param int $length number of bytes to read
+     * @return string|false raw bytes or false on eof
+     */
+    public function readBytes( $length ) {
+        $bytes = fread( $this->file, $length );
+        if ( feof( $this->file ) ) {
+            return false;
+        }
+        if ( $bytes === false || strlen( $bytes ) < $length ) {
+
+            throw new Exception( "Failed to read $length bytes from MP4 file" );
+        }
+        return $bytes;
+    }
+
+    /**
+     * @param int $length number of bytes to skip over
+     */
+    private function skipBytes( $length ) {
+        $retval = fseek( $this->file, $length, SEEK_CUR );
+        if ( $retval < 0 ) {
+            throw new Exception( "Failed to skip ahead $length bytes in MP4 file" );
+        }
+    }
+
+    /**
+     * @return int|false 32-bit integer value or false on eof
+     */
+    public function read32() {
+        $bytes = $this->readBytes( 4 );
+        if ( $bytes === false ) {
+            return $bytes;
+        }
+        $data = unpack( 'Nval', $bytes );
+        return $data['val'];
+    }
+
+    /**
+     * @return string|false 4-byte type code or false on eof
+     */
+    public function readType() {
+        return $this->readBytes( 4 );
+    }
+
+    /**
+     * @param callable $callback in the form function(MP4Box)
+     * @return mixed the return value from the callback, or false on eof
+     */
+    public function readBox( $callback ) {
+        $start = $this->pos();
+        $size = $this->read32();
+        if ( $size === false ) {
+            return false;
+        }
+        $end = $start + $size;
+
+        $type = $this->readType();
+        if ( $type === false ) {
+            return false;
+        }
+
+        $box = new MP4Box( $this, $start, $size, $type );
+        $retval = call_user_func( $callback, $box );
+
+        $remaining = $end - $this->pos();
+        if ( $remaining > 0 ) {
+            $this->skipBytes( $remaining );
+        }
+        return $retval;
+    }
+
+}
+
+class MP4Box {
+    private $reader;
+    public $start;
+    public $size;
+    public $type;
+
+    function __construct( MP4Reader $reader, $start, $size, $type ) {
+        $this->reader = $reader;
+        $this->start = $start;
+        $this->size = $size;
+        $this->type = $type;
+    }
+
+    private function pos() {
+        return $this->reader->pos();
+    }
+
+    private function end() {
+        return $this->start + $this->size;
+    }
+    
+    private function remaining() {
+        return $this->end() - $this->pos();
+    }
+
+    private function guard( $length ) {
+        $remaining = $this->remaining();
+        if ( $remaining < $length ) {
+            throw new Exception( "Reading beyond end of box; had $remaining bytes, wanted $length" );
+        }
+    }
+
+    public function readBytes( $length ) {
+        $this->guard( $length );
+        return $this->reader->readBytes( $length );
+    }
+
+    public function read32() {
+        $this->guard( 4 );
+        return $this->reader->read32();
+    }
+
+    public function readType() {
+        $this->guard( 4 );
+        return $this->reader->readType();
+    }
+
+    public function readBox( $callback ) {
+        $this->guard( 8 );
+        return $this->reader->readBox( $callback );
+    }
+}
+
+function hexdump( $str ) {
+    $out = '';
+    $len = strlen( $str );
+    for ( $i = 0; $i < $len; $i++ ) {
+        $char = $str[$i];
+        $byte = ord( $char );
+        // really?
+        $digits = str_pad( dechex( $byte ), 2, '0', STR_PAD_LEFT );
+        $out .= $digits;
+    }
+    return $out;
+}
+
+function safestr( $str ) {
+    $out = '';
+    $len = strlen( $str );
+    for ( $i = 0; $i < $len; $i++ ) {
+        $char = $str[$i];
+        $byte = ord( $char );
+        if ( $byte >= 32 && $byte <= 126 ) {
+            $out .= $char;
+        } else {
+            $out .= '.';
+        }
+    }
+    return $out;
+}
+
+/**
+ * @param string $filename - input MP4 file to read
+ * @return array[] - list of segment info
+ */
+function extractFragmentedMP4( $filename ) {
+    $segments = [];
+
+    $mp4 = new MP4Reader( $filename );
+    $eof = false;
+    $init = false;
+
+    while ( !$eof ) {
+        $eof = !$mp4->readBox( function ( $box ) use  ( &$segments, &$init ) {
+            $bytes = $box->readBytes( $box->size - 8 );
+            $bytes = substr( $bytes, 0, 16 );
+            $hex = hexdump( $bytes );
+            $safe = safestr( $bytes );
+            print "box: {$box->type} at {$box->start}, {$box->size} bytes {$hex} {$safe}\n";
+
+            /*
+            Need to:
+            - find the end of the moov; everything up to that is the initialization segment
+            - https://www.w3.org/TR/mse-byte-stream-format-isobmff/#iso-init-segments
+            - find the start of each styp+moof fragment
+            - https://www.w3.org/TR/mse-byte-stream-format-isobmff/#iso-media-segments
+            - find the start timestamp of each moof fragment
+            - find the duration of each moof fragment
+
+            moov.trak.mdia.mdhd.timescale - looks useful 12288 for 24fps?
+            moov.trak.mdia.mdhd.duration - 0 on the moov
+            moov.mvex.trex.default_sample_duration - 0 on the moov
+
+            moof.traf.tfhd.default_sample_duration is 512 on these
+            moof.traf.tfdt.baseMediaDecodeTime is 0 on the first, 122880 on the second frag (10 seconds in?)
+            moof.mdat.sample_duration is empty here (uses default I guess?)
+            moof.mdat.sample_composition_time_offset also empty
+
+
+            opus has timescale 48000 in moov.trak.mdia.mdhd
+
+            WARNING: opus is not dividing up fragments
+
+            */
+
+            if ( $box->type === 'moof' ) {
+                if ( !$init ) {
+                    $init = [
+                        'start' => 0,
+                        'size' => $box->start + $box->size,
+                    ];
+                    $segments['init'] = $init;
+                }
+                array_push( $segments, [
+                    'start' => $box->start,
+                    'size' => $box->size,
+                    'timestamp' => 0.0,
+                    'duration' => 0.0,
+                ] );
+            }
+
+            return true;
+        } );
+    }
+
+    return $segments;
+}
+
+$argv = $_SERVER['argv'];
+$self = array_shift( $argv );
+$filename = array_shift( $argv );
+$segments = extractFragmentedMP4( $filename );
+var_dump( $segments );
diff --git a/make-fmp4.sh b/make-fmp4.sh
new file mode 100755
index 0000000..07cfcb7
--- /dev/null
+++ b/make-fmp4.sh
@@ -0,0 +1,37 @@
+interval=10
+MOVFLAGS="-movflags +frag_keyframe+empty_moov -force_key_frames expr:gte(t,n_forced*$interval)"
+AUDFLAGS="-movflags +empty_moov -frag_duration ${interval}000000"
+BITRATE_HI="-b:v 1250k"
+BITRATE_LO="-b:v 1000k"
+
+SIZE_MAIN="-s 854x480"
+
+VIDEO_H264="-vcodec h264 -g 240 $BITRATE_HI $SIZE_MAIN"
+VIDEO_VP9="-vcodec libvpx-vp9 -tile-columns 2 -row-mt 1 -cpu-used 3 -g 240 $BITRATE_LO $SIZE_MAIN"
+
+AUDIO_OPUS="-acodec libopus -ac 2 -ar 48000 -ab 96k"
+AUDIO_AAC="-ac 2 -ar 44100 -ab 128k"
+AUDIO_MP3="-acodec libmp3lame -ac 2 -ar 44100 -ab 128k"
+
+INFILE=caminandes-llamigos.webm
+
+set -e
+
+# Audio for HLS
+ffmpeg -i $INFILE -vn $AUDIO_MP3 -y fmp4.audio.mp3
+ffmpeg -i $INFILE -vn $AUDIO_AAC $AUDFLAGS  -y fmp4.audio.aac.mp4
+ffmpeg -i $INFILE -vn $AUDIO_OPUS $AUDFLAGS -y fmp4.audio.opus.mp4
+
+# Video for HLS
+ffmpeg -i $INFILE -an $VIDEO_H264 $MOVFLAGS -pass 1 -y fmp4.video.h264.mp4
+ffmpeg -i $INFILE -an $VIDEO_H264 $MOVFLAGS -pass 2 -y fmp4.video.h264.mp4
+
+ffmpeg -i $INFILE -an $VIDEO_VP9 $MOVFLAGS -pass 1 -y fmp4.video.vp9.mp4
+ffmpeg -i $INFILE -an $VIDEO_VP9 $MOVFLAGS -pass 2 -y fmp4.video.vp9.mp4
+
+# Playlist processing
+#php extract-playlist.php fmp4.audio.mp3 fmp4.audio.mp3.m3u8
+#php extract-playlist.php fmp4.audio.aac.mp4 fmp4.audio.aac.mp4.m3u8
+#php extract-playlist.php fmp4.audio.opus.mp4 fmp4.audio.opus.mp4.m3u8
+#php extract-playlist.php fmp4.video.h264.mp4 fmp4.video.h264.mp4.m3u8
+#php extract-playlist.php fmp4.video.vp9.mp4 fmp4.video.vp9.mp4.m3u8