Mpeg.php

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<?php

namespace GetId3\Module\AudioVideo;

use GetId3\Handler\BaseHandler;
use GetId3\Lib\Helper;
use GetId3\Module\Audio\Mp3;

//  available at http://getid3.sourceforge.net                 //
//            or http://www.getid3.org                         //
// See readme.txt for more details                             //
//                                                             //
// module.audio-video.mpeg.php                                 //
// module for analyzing MPEG files                             //
// dependencies: module.audio.mp3.php                          //
//                                                            ///

class Mpeg extends BaseHandler
{
    const GETID3_MPEG_VIDEO_PICTURE_START = "\x00\x00\x01\x00";
    const GETID3_MPEG_VIDEO_USER_DATA_START = "\x00\x00\x01\xB2";
    const GETID3_MPEG_VIDEO_SEQUENCE_HEADER = "\x00\x00\x01\xB3";
    const GETID3_MPEG_VIDEO_SEQUENCE_ERROR = "\x00\x00\x01\xB4";
    const GETID3_MPEG_VIDEO_EXTENSION_START = "\x00\x00\x01\xB5";
    const GETID3_MPEG_VIDEO_SEQUENCE_END = "\x00\x00\x01\xB7";
    const GETID3_MPEG_VIDEO_GROUP_START = "\x00\x00\x01\xB8";
    const GETID3_MPEG_AUDIO_START = "\x00\x00\x01\xC0";

    public function analyze()
    {
        $info = &$this->getid3->info;

        if ($info['avdataend'] <= $info['avdataoffset']) {
            $info['error'][] = '"avdataend" (' . $info['avdataend'] . ') is unexpectedly less-than-or-equal-to "avdataoffset" (' . $info['avdataoffset'] . ')';

            return false;
        }
        $info['fileformat'] = 'mpeg';
        fseek($this->getid3->fp, $info['avdataoffset'], SEEK_SET);
        $MPEGstreamData = fread($this->getid3->fp,
                                min(100000,
                                    $info['avdataend'] - $info['avdataoffset']));
        $MPEGstreamDataLength = strlen($MPEGstreamData);

        $foundVideo = true;
        $VideoChunkOffset = 0;
        while (substr($MPEGstreamData, $VideoChunkOffset++, 4) !== self::GETID3_MPEG_VIDEO_SEQUENCE_HEADER) {
            if ($VideoChunkOffset >= $MPEGstreamDataLength) {
                $foundVideo = false;
                break;
            }
        }
        if ($foundVideo) {

            // Start code                       32 bits
            // horizontal frame size            12 bits
            // vertical frame size              12 bits
            // pixel aspect ratio                4 bits
            // frame rate                        4 bits
            // bitrate                          18 bits
            // marker bit                        1 bit
            // VBV buffer size                  10 bits
            // constrained parameter flag        1 bit
            // intra quant. matrix flag          1 bit
            // intra quant. matrix values      512 bits (present if matrix flag == 1)
            // non-intra quant. matrix flag      1 bit
            // non-intra quant. matrix values  512 bits (present if matrix flag == 1)

            $info['video']['dataformat'] = 'mpeg';

            $VideoChunkOffset += (strlen(self::GETID3_MPEG_VIDEO_SEQUENCE_HEADER) - 1);

            $FrameSizeDWORD = Helper::BigEndian2Int(substr($MPEGstreamData,
                                                                      $VideoChunkOffset,
                                                                      3));
            $VideoChunkOffset += 3;

            $AspectRatioFrameRateDWORD = Helper::BigEndian2Int(substr($MPEGstreamData,
                                                                                 $VideoChunkOffset,
                                                                                 1));
            $VideoChunkOffset += 1;

            $assortedinformation = Helper::BigEndian2Bin(substr($MPEGstreamData,
                                                                           $VideoChunkOffset,
                                                                           4));
            $VideoChunkOffset += 4;

            $info['mpeg']['video']['raw']['framesize_horizontal'] = ($FrameSizeDWORD & 0xFFF000) >> 12; // 12 bits for horizontal frame size
            $info['mpeg']['video']['raw']['framesize_vertical'] = ($FrameSizeDWORD & 0x000FFF);       // 12 bits for vertical frame size
            $info['mpeg']['video']['raw']['pixel_aspect_ratio'] = ($AspectRatioFrameRateDWORD & 0xF0) >> 4;
            $info['mpeg']['video']['raw']['frame_rate'] = ($AspectRatioFrameRateDWORD & 0x0F);

            $info['mpeg']['video']['framesize_horizontal'] = $info['mpeg']['video']['raw']['framesize_horizontal'];
            $info['mpeg']['video']['framesize_vertical'] = $info['mpeg']['video']['raw']['framesize_vertical'];

            $info['mpeg']['video']['pixel_aspect_ratio'] = $this->MPEGvideoAspectRatioLookup($info['mpeg']['video']['raw']['pixel_aspect_ratio']);
            $info['mpeg']['video']['pixel_aspect_ratio_text'] = $this->MPEGvideoAspectRatioTextLookup($info['mpeg']['video']['raw']['pixel_aspect_ratio']);
            $info['mpeg']['video']['frame_rate'] = $this->MPEGvideoFramerateLookup($info['mpeg']['video']['raw']['frame_rate']);

            $info['mpeg']['video']['raw']['bitrate'] = Helper::Bin2Dec(substr($assortedinformation,
                                                                                         0,
                                                                                         18));
            $info['mpeg']['video']['raw']['marker_bit'] = (bool) Helper::Bin2Dec(substr($assortedinformation,
                                                                                                   18,
                                                                                                   1));
            $info['mpeg']['video']['raw']['vbv_buffer_size'] = Helper::Bin2Dec(substr($assortedinformation,
                                                                                                 19,
                                                                                                 10));
            $info['mpeg']['video']['raw']['constrained_param_flag'] = (bool) Helper::Bin2Dec(substr($assortedinformation,
                                                                                                               29,
                                                                                                               1));
            $info['mpeg']['video']['raw']['intra_quant_flag'] = (bool) Helper::Bin2Dec(substr($assortedinformation,
                                                                                                         30,
                                                                                                         1));
            if ($info['mpeg']['video']['raw']['intra_quant_flag']) {

                // read 512 bits
                $info['mpeg']['video']['raw']['intra_quant'] = Helper::BigEndian2Bin(substr($MPEGstreamData,
                                                                                                       $VideoChunkOffset,
                                                                                                       64));
                $VideoChunkOffset += 64;

                $info['mpeg']['video']['raw']['non_intra_quant_flag'] = (bool) Helper::Bin2Dec(substr($info['mpeg']['video']['raw']['intra_quant'],
                                                                                                                 511,
                                                                                                                 1));
                $info['mpeg']['video']['raw']['intra_quant'] = Helper::Bin2Dec(substr($assortedinformation,
                                                                                                 31,
                                                                                                 1)) . substr(Helper::BigEndian2Bin(substr($MPEGstreamData,
                                                                                                                                                      $VideoChunkOffset,
                                                                                                                                                      64)),
                                                                                                                                                      0,
                                                                                                                                                      511);

                if ($info['mpeg']['video']['raw']['non_intra_quant_flag']) {
                    $info['mpeg']['video']['raw']['non_intra_quant'] = substr($MPEGstreamData,
                                                                              $VideoChunkOffset,
                                                                              64);
                    $VideoChunkOffset += 64;
                }
            } else {

                $info['mpeg']['video']['raw']['non_intra_quant_flag'] = (bool) Helper::Bin2Dec(substr($assortedinformation,
                                                                                                                 31,
                                                                                                                 1));
                if ($info['mpeg']['video']['raw']['non_intra_quant_flag']) {
                    $info['mpeg']['video']['raw']['non_intra_quant'] = substr($MPEGstreamData,
                                                                              $VideoChunkOffset,
                                                                              64);
                    $VideoChunkOffset += 64;
                }
            }

            if ($info['mpeg']['video']['raw']['bitrate'] == 0x3FFFF) { // 18 set bits
                $info['warning'][] = 'This version of GetId3Core() [' . $this->getid3->version() . '] cannot determine average bitrate of VBR MPEG video files';
                $info['mpeg']['video']['bitrate_mode'] = 'vbr';
            } else {

                $info['mpeg']['video']['bitrate'] = $info['mpeg']['video']['raw']['bitrate'] * 400;
                $info['mpeg']['video']['bitrate_mode'] = 'cbr';
                $info['video']['bitrate'] = $info['mpeg']['video']['bitrate'];
            }

            $info['video']['resolution_x'] = $info['mpeg']['video']['framesize_horizontal'];
            $info['video']['resolution_y'] = $info['mpeg']['video']['framesize_vertical'];
            $info['video']['frame_rate'] = $info['mpeg']['video']['frame_rate'];
            $info['video']['bitrate_mode'] = $info['mpeg']['video']['bitrate_mode'];
            $info['video']['pixel_aspect_ratio'] = $info['mpeg']['video']['pixel_aspect_ratio'];
            $info['video']['lossless'] = false;
            $info['video']['bits_per_sample'] = 24;
        } else {

            $info['error'][] = 'Could not find start of video block in the first 100,000 bytes (or before end of file) - this might not be an MPEG-video file?';
        }

        //0x000001B3 begins the sequence_header of every MPEG video stream.
        //But in MPEG-2, this header must immediately be followed by an
        //extension_start_code (0x000001B5) with a sequence_extension ID (1).
        //(This extension contains all the additional MPEG-2 stuff.)
        //MPEG-1 doesn't have this extension, so that's a sure way to tell the
        //difference between MPEG-1 and MPEG-2 video streams.

        if (substr($MPEGstreamData, $VideoChunkOffset, 4) == self::GETID3_MPEG_VIDEO_EXTENSION_START) {
            $info['video']['codec'] = 'MPEG-2';
        } else {
            $info['video']['codec'] = 'MPEG-1';
        }

        $AudioChunkOffset = 0;
        while (true) {
            while (substr($MPEGstreamData, $AudioChunkOffset++, 4) !== self::GETID3_MPEG_AUDIO_START) {
                if ($AudioChunkOffset >= $MPEGstreamDataLength) {
                    break 2;
                }
            }

            $getid3_temp = new GetId3Core();
            $getid3_temp->openfile($this->getid3->filename);
            $getid3_temp->info = $info;
            $getid3_mp3 = new Mp3($getid3_temp);
            for ($i = 0; $i <= 7; $i++) {
                // some files have the MPEG-audio header 8 bytes after the end of the $00 $00 $01 $C0 signature, some have it up to 13 bytes (or more?) after
                // I have no idea why or what the difference is, so this is a stupid hack.
                // If anybody has any better idea of what's going on, please let me know - info@getid3.org
                fseek($getid3_temp->fp, ftell($this->getid3->fp), SEEK_SET);
                $getid3_temp->info = $info; // only overwrite real data if valid header found
                if ($getid3_mp3->decodeMPEGaudioHeader(($AudioChunkOffset + 3) + 8 + $i,
                                                       $getid3_temp->info, false)) {
                    $info = $getid3_temp->info;
                    $info['audio']['bitrate_mode'] = 'cbr';
                    $info['audio']['lossless'] = false;
                    unset($getid3_temp, $getid3_mp3);
                    break 2;
                }
            }
            unset($getid3_temp, $getid3_mp3);
        }

        // Temporary hack to account for interleaving overhead:
        if (!empty($info['video']['bitrate']) && !empty($info['audio']['bitrate'])) {
            $info['playtime_seconds'] = (($info['avdataend'] - $info['avdataoffset']) * 8) / ($info['video']['bitrate'] + $info['audio']['bitrate']);

            // Interleaved MPEG audio/video files have a certain amount of overhead that varies
            // by both video and audio bitrates, and not in any sensible, linear/logarithmic patter
            // Use interpolated lookup tables to approximately guess how much is overhead, because
            // playtime is calculated as filesize / total-bitrate
            $info['playtime_seconds'] *= $this->MPEGsystemNonOverheadPercentage($info['video']['bitrate'],
                                                                                $info['audio']['bitrate']);

            //switch ($info['video']['bitrate']) {
            //  case('5000000'):
            //          $multiplier = 0.93292642112380355828048824319889;
            //          break;
            //  case('5500000'):
            //          $multiplier = 0.93582895375200989965359777343219;
            //          break;
            //  case('6000000'):
            //          $multiplier = 0.93796247714820932532911373859139;
            //          break;
            //  case('7000000'):
            //          $multiplier = 0.9413264083635103463010117778776;
            //          break;
            //  default:
            //          $multiplier = 1;
            //          break;
            //}
            //$info['playtime_seconds'] *= $multiplier;
            //$info['warning'][] = 'Interleaved MPEG audio/video playtime may be inaccurate. With current hack should be within a few seconds of accurate. Report to info@getid3.org if off by more than 10 seconds.';
            if ($info['video']['bitrate'] < 50000) {
                $info['warning'][] = 'Interleaved MPEG audio/video playtime may be slightly inaccurate for video bitrates below 100kbps. Except in extreme low-bitrate situations, error should be less than 1%. Report to info@getid3.org if greater than this.';
            }
        }

        return true;
    }

    public function MPEGsystemNonOverheadPercentage($VideoBitrate, $AudioBitrate)
    {
        $OverheadPercentage = 0;

        $AudioBitrate = max(min($AudioBitrate / 1000, 384), 32); // limit to range of 32kbps - 384kbps (should be only legal bitrates, but maybe VBR?)
        $VideoBitrate = max(min($VideoBitrate / 1000, 10000), 10); // limit to range of 10kbps -  10Mbps (beyond that curves flatten anyways, no big loss)
        //OMBB[audiobitrate]              = array(video-10kbps,       video-100kbps,      video-1000kbps,     video-10000kbps)
        $OverheadMultiplierByBitrate[32] = array(0, 0.9676287944368530, 0.9802276264360310, 0.9844916183244460, 0.9852821845179940);
        $OverheadMultiplierByBitrate[48] = array(0, 0.9779100089209830, 0.9787770035359320, 0.9846738664076130, 0.9852683013799960);
        $OverheadMultiplierByBitrate[56] = array(0, 0.9731249855367600, 0.9776624308938040, 0.9832606361852130, 0.9843922606633340);
        $OverheadMultiplierByBitrate[64] = array(0, 0.9755642683275760, 0.9795256705493390, 0.9836573009193170, 0.9851122539404470);
        $OverheadMultiplierByBitrate[96] = array(0, 0.9788025247497290, 0.9798553314148700, 0.9822956869792560, 0.9834815119124690);
        $OverheadMultiplierByBitrate[128] = array(0, 0.9816940050925480, 0.9821675936072120, 0.9829756927470870, 0.9839763420152050);
        $OverheadMultiplierByBitrate[160] = array(0, 0.9825894094561180, 0.9820913399073960, 0.9823907143253970, 0.9832821783651570);
        $OverheadMultiplierByBitrate[192] = array(0, 0.9832038474336260, 0.9825731694317960, 0.9821028622712400, 0.9828262076447620);
        $OverheadMultiplierByBitrate[224] = array(0, 0.9836516298538770, 0.9824718601823890, 0.9818302180625380, 0.9823735101626480);
        $OverheadMultiplierByBitrate[256] = array(0, 0.9845863022094920, 0.9837229411967540, 0.9824521662210830, 0.9828645172100790);
        $OverheadMultiplierByBitrate[320] = array(0, 0.9849565280263180, 0.9837683142805110, 0.9822885275960400, 0.9824424382727190);
        $OverheadMultiplierByBitrate[384] = array(0, 0.9856094774357600, 0.9844573394432720, 0.9825970399837330, 0.9824673808303890);

        $BitrateToUseMin = 32;
        $BitrateToUseMax = 32;
        $previousBitrate = 32;
        foreach ($OverheadMultiplierByBitrate as $key => $value) {
            if ($AudioBitrate >= $previousBitrate) {
                $BitrateToUseMin = $previousBitrate;
            }
            if ($AudioBitrate < $key) {
                $BitrateToUseMax = $key;
                break;
            }
            $previousBitrate = $key;
        }
        $FactorA = ($BitrateToUseMax - $AudioBitrate) / ($BitrateToUseMax - $BitrateToUseMin);

        $VideoBitrateLog10 = log10($VideoBitrate);
        $VideoFactorMin1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][floor($VideoBitrateLog10)];
        $VideoFactorMin2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][floor($VideoBitrateLog10)];
        $VideoFactorMax1 = $OverheadMultiplierByBitrate[$BitrateToUseMin][ceil($VideoBitrateLog10)];
        $VideoFactorMax2 = $OverheadMultiplierByBitrate[$BitrateToUseMax][ceil($VideoBitrateLog10)];
        $FactorV = $VideoBitrateLog10 - floor($VideoBitrateLog10);

        $OverheadPercentage = $VideoFactorMin1 * $FactorA * $FactorV;
        $OverheadPercentage += $VideoFactorMin2 * (1 - $FactorA) * $FactorV;
        $OverheadPercentage += $VideoFactorMax1 * $FactorA * (1 - $FactorV);
        $OverheadPercentage += $VideoFactorMax2 * (1 - $FactorA) * (1 - $FactorV);

        return $OverheadPercentage;
    }

    public function MPEGvideoFramerateLookup($rawframerate)
    {
        $MPEGvideoFramerateLookup = array(0, 23.976, 24, 25, 29.97, 30, 50, 59.94, 60);

        return (isset($MPEGvideoFramerateLookup[$rawframerate]) ? (float) $MPEGvideoFramerateLookup[$rawframerate] : (float) 0);
    }

    public function MPEGvideoAspectRatioLookup($rawaspectratio)
    {
        $MPEGvideoAspectRatioLookup = array(0, 1, 0.6735, 0.7031, 0.7615, 0.8055, 0.8437, 0.8935, 0.9157, 0.9815, 1.0255, 1.0695, 1.0950, 1.1575, 1.2015, 0);

        return (isset($MPEGvideoAspectRatioLookup[$rawaspectratio]) ? (float) $MPEGvideoAspectRatioLookup[$rawaspectratio] : (float) 0);
    }

    public function MPEGvideoAspectRatioTextLookup($rawaspectratio)
    {
        $MPEGvideoAspectRatioTextLookup = array('forbidden', 'square pixels', '0.6735', '16:9, 625 line, PAL', '0.7615', '0.8055', '16:9, 525 line, NTSC', '0.8935', '4:3, 625 line, PAL, CCIR601', '0.9815', '1.0255', '1.0695', '4:3, 525 line, NTSC, CCIR601', '1.1575', '1.2015', 'reserved');

        return (isset($MPEGvideoAspectRatioTextLookup[$rawaspectratio]) ? $MPEGvideoAspectRatioTextLookup[$rawaspectratio] : '');
    }
}