Code Coverage |
||||||||||
Lines |
Functions and Methods |
Classes and Traits |
||||||||
| Total | |
50.68% |
74 / 146 |
|
16.67% |
1 / 6 |
CRAP | |
0.00% |
0 / 1 |
| MP3Segmenter | |
50.68% |
74 / 146 |
|
16.67% |
1 / 6 |
86.44 | |
0.00% |
0 / 1 |
| field | |
100.00% |
3 / 3 |
|
100.00% |
1 / 1 |
1 | |||
| frameHeader | |
85.29% |
29 / 34 |
|
0.00% |
0 / 1 |
7.16 | |||
| id3Header | |
85.71% |
12 / 14 |
|
0.00% |
0 / 1 |
3.03 | |||
| parse | |
96.77% |
30 / 31 |
|
0.00% |
0 / 1 |
5 | |||
| rewrite | |
0.00% |
0 / 24 |
|
0.00% |
0 / 1 |
12 | |||
| timestampTag | |
0.00% |
0 / 40 |
|
0.00% |
0 / 1 |
20 | |||
| 1 | <?php |
| 2 | /** |
| 3 | * .m3u8 playlist generation for HLS (HTTP Live Streaming) |
| 4 | * |
| 5 | * @file |
| 6 | * @ingroup HLS |
| 7 | */ |
| 8 | |
| 9 | namespace MediaWiki\TimedMediaHandler\HLS; |
| 10 | |
| 11 | use RuntimeException; |
| 12 | |
| 13 | /** |
| 14 | * Reads an MP3 file calculating the byte and time boundaries |
| 15 | * of the separate addressable frames, allowing creation of a |
| 16 | * streaming playlist. |
| 17 | * |
| 18 | * Optionally can rewrite the file to insert timestamp ID3 tags |
| 19 | * which Apple's HLS says it wants in raw packet streams. Note |
| 20 | * that initially the parse() result will make every addressible |
| 21 | * frame (and any source ID3 tags ahead of it) an individual segment. |
| 22 | * Before inserting timestamp tags with rewrite(), make a call to |
| 23 | * consolidate($segmentLength). |
| 24 | * |
| 25 | * Because the relevant ISO standards are not redistributable, |
| 26 | * artisanal 3rd-party documentation was sourced via web searches |
| 27 | * such as: |
| 28 | * - https://en.wikipedia.org/wiki/MP3 |
| 29 | * - http://www.mp3-tech.org/programmer/frame_header.html |
| 30 | * - https://datatracker.ietf.org/doc/html/rfc8216 |
| 31 | * - https://id3.org/id3v2.4.0-frames |
| 32 | * - https://id3.org/id3v2.4.0-structure |
| 33 | * - https://web.archive.org/web/20081008034714/http://www.id3.org/id3v2.3.0 |
| 34 | */ |
| 35 | class MP3Segmenter extends Segmenter { |
| 36 | |
| 37 | /** |
| 38 | * Internal layout of MP3 frame header bitfield |
| 39 | * @var array |
| 40 | */ |
| 41 | private static $bits = [ |
| 42 | 'sync' => [ 21, 11 ], |
| 43 | 'mpeg' => [ 19, 2 ], |
| 44 | 'layer' => [ 17, 2 ], |
| 45 | 'protection' => [ 16, 1 ], |
| 46 | 'bitrate' => [ 12, 4 ], |
| 47 | 'sampleRate' => [ 10, 2 ], |
| 48 | 'padding' => [ 9, 1 ], |
| 49 | // below this not needed at present |
| 50 | 'private' => [ 8, 1 ], |
| 51 | 'channelMode' => [ 6, 2 ], |
| 52 | 'modeExt' => [ 4, 2 ], |
| 53 | 'copyright' => [ 3, 1 ], |
| 54 | 'original' => [ 2, 1 ], |
| 55 | 'emphasis' => [ 0, 2 ], |
| 56 | ]; |
| 57 | |
| 58 | /** |
| 59 | * 11-bit sync mask for MP3 frame header |
| 60 | * @var int |
| 61 | */ |
| 62 | private const SYNC_MASK = 0x7ff; |
| 63 | |
| 64 | /** |
| 65 | * Map of sample count per frame based on version/mode |
| 66 | * This is just in case we need to measure non-default sample rates! |
| 67 | * @var array |
| 68 | */ |
| 69 | private static $samplesPerFrame = [ |
| 70 | // invalid / layer 3 / 2 / 1 |
| 71 | |
| 72 | // MPEG-2.5 |
| 73 | [ 0, 576, 1152, 384 ], |
| 74 | // Reserved |
| 75 | [ 0, 0, 0, 0 ], |
| 76 | // MPEG-2 |
| 77 | [ 0, 576, 1152, 384 ], |
| 78 | // MPEG-1 |
| 79 | [ 0, 1152, 384, 384 ], |
| 80 | ]; |
| 81 | |
| 82 | /** |
| 83 | * Map of sample rates based on version/mode |
| 84 | * @var array |
| 85 | */ |
| 86 | private static $sampleRates = [ |
| 87 | // MPEG-2.5 |
| 88 | [ 11025, 12000, 8000, 1 ], |
| 89 | // Reserved |
| 90 | [ 1, 1, 1, 1 ], |
| 91 | // MPEG-2 |
| 92 | [ 22050, 24000, 16000, 1 ], |
| 93 | // MPEG-1 |
| 94 | [ 44100, 48000, 32000, 1 ], |
| 95 | ]; |
| 96 | |
| 97 | /** |
| 98 | * Map of bit rates based on version/mode/code |
| 99 | * @var array |
| 100 | */ |
| 101 | private static $bitrates = [ |
| 102 | // MPEG-2 |
| 103 | [ |
| 104 | // invalid layer |
| 105 | [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ], |
| 106 | // layer 3 |
| 107 | [ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 ], |
| 108 | // layer 2 |
| 109 | [ 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0 ], |
| 110 | // layer 1 |
| 111 | [ 0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0 ], |
| 112 | ], |
| 113 | // MPEG-1 |
| 114 | [ |
| 115 | // invalid layer |
| 116 | [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ], |
| 117 | // layer 3 |
| 118 | [ 0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 192, 224, 256, 320, 0 ], |
| 119 | // layer 2 |
| 120 | [ 0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0 ], |
| 121 | // layer 1 |
| 122 | [ 0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 316, 448, 0 ], |
| 123 | ] |
| 124 | ]; |
| 125 | |
| 126 | /** |
| 127 | * Timestamp resolution for HLS ID3 timestamp tags |
| 128 | */ |
| 129 | private const KHZ_90 = 90000; |
| 130 | |
| 131 | /** |
| 132 | * Decode a binary field from the MP3 frame header |
| 133 | */ |
| 134 | private static function field( string $name, int $header ): int { |
| 135 | [ $shift, $bits ] = self::$bits[$name]; |
| 136 | $mask = ( 1 << $bits ) - 1; |
| 137 | return ( $header >> $shift ) & $mask; |
| 138 | } |
| 139 | |
| 140 | /** |
| 141 | * Decode an MP3 header bitfield |
| 142 | */ |
| 143 | private static function frameHeader( string $bytes ): ?array { |
| 144 | if ( strlen( $bytes ) < 4 ) { |
| 145 | return null; |
| 146 | } |
| 147 | $data = unpack( "Nval", $bytes ); |
| 148 | $header = $data['val']; |
| 149 | |
| 150 | // This includes "MPEG 2.5" support, so checks for 11 set bits |
| 151 | // not 12 set bits as per original MPEG 1/2 |
| 152 | $sync = self::field( 'sync', $header ); |
| 153 | if ( $sync !== self::SYNC_MASK ) { |
| 154 | return null; |
| 155 | } |
| 156 | |
| 157 | $mpeg = self::field( 'mpeg', $header ); |
| 158 | $layer = self::field( 'layer', $header ); |
| 159 | $protection = self::field( 'protection', $header ); |
| 160 | |
| 161 | $br = self::field( 'bitrate', $header ); |
| 162 | $bitrate = 1000 * self::$bitrates[$mpeg & 1][$layer][$br]; |
| 163 | if ( $bitrate === 0 ) { |
| 164 | return null; |
| 165 | } |
| 166 | |
| 167 | $sr = self::field( 'sampleRate', $header ); |
| 168 | $sampleRate = self::$sampleRates[$mpeg][$sr]; |
| 169 | if ( $sampleRate === 1 ) { |
| 170 | return null; |
| 171 | } |
| 172 | |
| 173 | $padding = self::field( 'padding', $header ); |
| 174 | |
| 175 | $samples = self::$samplesPerFrame[$mpeg][$layer]; |
| 176 | $duration = $samples / $sampleRate; |
| 177 | $nbits = $duration * $bitrate; |
| 178 | $nbytes = $nbits / 8; |
| 179 | $size = intval( $nbytes ); |
| 180 | |
| 181 | if ( $protection === 0 ) { |
| 182 | $size += 2; |
| 183 | } |
| 184 | if ( $padding === 1 ) { |
| 185 | $size++; |
| 186 | } |
| 187 | |
| 188 | return [ |
| 189 | 'samples' => $samples, |
| 190 | 'sampleRate' => $sampleRate, |
| 191 | 'size' => $size, |
| 192 | 'duration' => $duration, |
| 193 | ]; |
| 194 | } |
| 195 | |
| 196 | private static function id3Header( string $bytes ): ?array { |
| 197 | // ID3v2.3 |
| 198 | // https://web.archive.org/web/20081008034714/http://www.id3.org/id3v2.3.0 |
| 199 | // ID3v2/file identifier "ID3" |
| 200 | // ID3v2 version $03 00 |
| 201 | // ID3v2 flags %abc00000 |
| 202 | // ID3v2 size 4 * %0xxxxxxx |
| 203 | $headerLen = 10; |
| 204 | if ( strlen( $bytes ) < $headerLen ) { |
| 205 | return null; |
| 206 | } |
| 207 | |
| 208 | $data = unpack( "a3tag/nversion/Cflags/C4size", $bytes ); |
| 209 | if ( $data['tag'] !== 'ID3' ) { |
| 210 | return null; |
| 211 | } |
| 212 | |
| 213 | $size = $headerLen + |
| 214 | ( $data['size4'] | |
| 215 | ( $data['size3'] << 7 ) | |
| 216 | ( $data['size2'] << 14 ) | |
| 217 | ( $data['size1'] << 21 ) ); |
| 218 | return [ |
| 219 | 'size' => $size, |
| 220 | ]; |
| 221 | } |
| 222 | |
| 223 | protected function parse(): void { |
| 224 | $file = fopen( $this->filename, 'rb' ); |
| 225 | $stream = new OwningStreamReader( $file ); |
| 226 | |
| 227 | $timestamp = 0.0; |
| 228 | while ( true ) { |
| 229 | $start = $stream->pos(); |
| 230 | $lookahead = 10; |
| 231 | try { |
| 232 | $bytes = $stream->read( $lookahead ); |
| 233 | } catch ( ShortReadException $e ) { |
| 234 | // end of file |
| 235 | break; |
| 236 | } |
| 237 | |
| 238 | // Check for MP3 frame header sync pattern |
| 239 | $header = self::frameHeader( $bytes ); |
| 240 | if ( $header ) { |
| 241 | // Note we don't need the data at this time. |
| 242 | $stream->seek( $start + $header['size'] ); |
| 243 | $timestamp += $header['duration']; |
| 244 | $this->segments[] = [ |
| 245 | 'start' => $start, |
| 246 | 'size' => $header['size'], |
| 247 | 'timestamp' => $timestamp, |
| 248 | 'duration' => $header['duration'], |
| 249 | ]; |
| 250 | continue; |
| 251 | } |
| 252 | |
| 253 | // Check for ID3v2 tag |
| 254 | $id3 = self::id3Header( $bytes ); |
| 255 | if ( $id3 ) { |
| 256 | // For byte range purposes; count as zero duration |
| 257 | $stream->seek( $start + $id3['size'] ); |
| 258 | $this->segments[] = [ |
| 259 | 'start' => $start, |
| 260 | 'size' => $id3['size'], |
| 261 | 'timestamp' => $timestamp, |
| 262 | 'duration' => 0.0, |
| 263 | ]; |
| 264 | continue; |
| 265 | } |
| 266 | |
| 267 | throw new RuntimeException( "Not a valid MP3 or ID3 frame at $start" ); |
| 268 | } |
| 269 | } |
| 270 | |
| 271 | /** |
| 272 | * Rewrite the file to include ID3 private tags with timestamp |
| 273 | * data for HLS at segment boundaries. This will modify the file |
| 274 | * in-place and change the segment offsets and sizes in the object. |
| 275 | * |
| 276 | * Beware that an i/o error during modification of the file could |
| 277 | * leave the file in an inconsistent state. Short read exceptions |
| 278 | * should be impossible unless the file is being modified from under |
| 279 | * us. |
| 280 | */ |
| 281 | public function rewrite(): void { |
| 282 | $offset = 0; |
| 283 | $id3s = []; |
| 284 | $segments = []; |
| 285 | foreach ( $this->segments as $i => $orig ) { |
| 286 | $id3 = self::timestampTag( $orig['timestamp'] ); |
| 287 | $delta = strlen( $id3 ); |
| 288 | $id3s[$i] = $id3; |
| 289 | $segments[$i] = [ |
| 290 | 'start' => $orig['start'] + $offset, |
| 291 | 'size' => $orig['size'] + $delta, |
| 292 | 'timestamp' => $orig['timestamp'], |
| 293 | 'duration' => $orig['duration'], |
| 294 | ]; |
| 295 | $offset += $delta; |
| 296 | } |
| 297 | |
| 298 | $file = fopen( $this->filename, 'rw+b' ); |
| 299 | $stream = new OwningStreamReader( $file ); |
| 300 | |
| 301 | // Move each segment forward, starting at the lastmost to work in-place. |
| 302 | $preserveKeys = true; |
| 303 | foreach ( array_reverse( $this->segments, $preserveKeys ) as $i => $orig ) { |
| 304 | $stream->seek( $orig['start'] ); |
| 305 | $bytes = $stream->read( $orig['size'] ); |
| 306 | |
| 307 | $stream->seek( $segments[$i]['start'] ); |
| 308 | $stream->write( $id3s[$i] ); |
| 309 | $stream->write( $bytes ); |
| 310 | } |
| 311 | |
| 312 | $this->segments = $segments; |
| 313 | } |
| 314 | |
| 315 | /** |
| 316 | * Generate an ID3 private tag with a timestamp for use in HLS |
| 317 | * streams of raw media data such as MP3 or AAC. |
| 318 | */ |
| 319 | protected static function timestampTag( float $timestamp ): string { |
| 320 | /* |
| 321 | https://datatracker.ietf.org/doc/html/rfc8216 |
| 322 | PRIV frame type |
| 323 | |
| 324 | should contain: |
| 325 | |
| 326 | The ID3 PRIV owner identifier MUST be |
| 327 | "com.apple.streaming.transportStreamTimestamp". The ID3 payload MUST |
| 328 | be a 33-bit MPEG-2 Program Elementary Stream timestamp expressed as a |
| 329 | big-endian eight-octet number, with the upper 31 bits set to zero. |
| 330 | Clients SHOULD NOT play Packed Audio Segments without this ID3 tag. |
| 331 | |
| 332 | https://id3.org/id3v2.4.0-frames |
| 333 | https://id3.org/id3v2.4.0-structure |
| 334 | |
| 335 | bit order is MSB first, big-endian |
| 336 | |
| 337 | header 10 bytes |
| 338 | extended header (var, optional) |
| 339 | frames (variable) |
| 340 | pading (variable, optional) |
| 341 | footer (10 bytes, optional) |
| 342 | |
| 343 | |
| 344 | header: |
| 345 | "ID3" |
| 346 | version: 16 bits $04 00 |
| 347 | flags: 32 bits |
| 348 | idv2 size: 32 bits (in chunks of 4 bytes, not counting header or footer) |
| 349 | |
| 350 | flags: |
| 351 | bit 7 - unsyncrhonization (??) |
| 352 | bit 6 - extended header |
| 353 | bit 5 - experimental indicator |
| 354 | bit 4 - footer present |
| 355 | |
| 356 | frame: |
| 357 | id - 32 bits (four chars) |
| 358 | size - 32 bits (in chunks of 4 bytes, excluding frame header) |
| 359 | flags - 16 bits |
| 360 | (frame data) |
| 361 | |
| 362 | priv payload: |
| 363 | owner text string followed by \x00 |
| 364 | (binary data) |
| 365 | |
| 366 | The timestamps... I think... have 90 kHz integer resolution |
| 367 | so convert from the decimal seconds in the HLS |
| 368 | |
| 369 | */ |
| 370 | |
| 371 | $owner = "com.apple.streaming.transportStreamTimestamp\x00"; |
| 372 | $pts = round( $timestamp * self::KHZ_90 ); |
| 373 | $thirtyThreeBits = pow( 2, 33 ); |
| 374 | $thirtyOneBits = pow( 2, 31 ); |
| 375 | if ( $pts >= $thirtyThreeBits ) { |
| 376 | // make sure they won't get too big for 33 bits |
| 377 | // this allows about a 24 hour media length |
| 378 | throw new RuntimeException( "Timestamp overflow in MP3 output stream: $pts >= $thirtyThreeBits" ); |
| 379 | } |
| 380 | $pts_high = intval( floor( $pts / $thirtyOneBits ) ); |
| 381 | $pts_low = intval( $pts - ( $pts_high * $thirtyOneBits ) ); |
| 382 | |
| 383 | // Private frame payload |
| 384 | $frame_data = pack( |
| 385 | 'a*NN', |
| 386 | $owner, |
| 387 | $pts_high, |
| 388 | $pts_low, |
| 389 | ); |
| 390 | |
| 391 | // Private frame header |
| 392 | $frame_type = 'PRIV'; |
| 393 | $frame_flags = 0; |
| 394 | $frame_length = strlen( $frame_data ); |
| 395 | if ( $frame_length > 127 ) { |
| 396 | throw new RuntimeException( "Should never happen: too large ID3 frame data" ); |
| 397 | } |
| 398 | $frame = pack( |
| 399 | 'a4Nna*', |
| 400 | $frame_type, |
| 401 | $frame_length, |
| 402 | $frame_flags, |
| 403 | $frame_data |
| 404 | ); |
| 405 | |
| 406 | // ID3 tag |
| 407 | $tag_type = 'ID3'; |
| 408 | $tag_version = 0x0400; |
| 409 | $tag_flags = 0; |
| 410 | // if >127 bytes may need to adjust |
| 411 | $tag_length = strlen( $frame ); |
| 412 | if ( $tag_length > 127 ) { |
| 413 | throw new RuntimeException( "Should never happen: too large ID3 tag" ); |
| 414 | } |
| 415 | return pack( |
| 416 | 'a3nCNa*', |
| 417 | $tag_type, |
| 418 | $tag_version, |
| 419 | $tag_flags, |
| 420 | $tag_length, |
| 421 | $frame |
| 422 | ); |
| 423 | } |
| 424 | } |