src/mpeg/MPEGfile.cc

/*
    MPEG Maaate: An Australian MPEG audio analysis toolkit
    Copyright (C) 2000 Commonwealth Scientific and Industrial Research Organisation
    (CSIRO), Australia.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#if HAVE_CONFIG_H
#include <config.h>
#endif

#include "MPEGfile.H"

#include "layer1.H"
#include "layer2.H"
#include "layer3.H"

#include "byteOrder.h"

/*---------- constructor and destructor ---------------*/

// constructor
CSAPI_MPEG
MPEGfile::MPEGfile(string filenm) {

  //MPEG specifics attributs
  analysed   = false;
  decoded    = dec_fields;
  audio      = 0;
  lastlayer  = RESERVED;
  frameNo    = 0;
  gr_current = -1;

  // call the common constructor in AllFormat class
  // which initialises the variables
  //   filename, windowNo, fileDuration, windowDuration
  if(!common_constr(filenm))
    return;

  // open file and save file descriptor in AllFormat's fd variable
  if ((fd = fopen (filename.c_str(), "rb")) == NULL) {
    cerr << "MaaateMPEG: Cannot open file ";
    cerr  << filename.c_str() << "." << endl;
    return;
  }

  if (!skip_frame()) //not a MPEG file
    return;

  // calculate the duration of the file and store it
  while (skip_frame());
  fileDuration = frameNo * nb_granules();
  windowNo     = fileDuration;

  //calculate windowDuration
  windowDuration = timeticks(LOW) * sample_duration(LOW);

  // reset to start of file
  seek_window(0);
  if (layer()==III) {
	((Layer3*) audio)->clearinterbuffer();
  }

  return;
}

// destructor
CSAPI_MPEG
MPEGfile::~MPEGfile() {

  common_destr();

  if (fd)
    fclose (fd);

  if (audio) delete audio;
  audio=0;
}


/*---------------- About this file -----------------*/

CSAPI_MPEG bool
MPEGfile::file_ok() {
  if (fd == NULL) {
    return false;
  }
  if (fileDuration <=0) {
    return false;
  }
  return true;
}

CSAPI_MPEG bool
MPEGfile::is_stereo() {
  return  ( mode() <= jstereo); //either stereo or jstereo
}

CSAPI_MPEG int
MPEGfile::channel() {
  return channels();
}

CSAPI_MPEG double
MPEGfile::sampling_rate() {
  return samplingrate();
}


/*---------------- time functions --------------------*/

CSAPI_MPEG float
MPEGfile::sample_duration( Resolution res ) {
  //duration of one MPEG frame
  double frameDur = (1.0*samples_per_frame() / (1000.0 * samplingrate()));

  if ( res == PCM ) {
    return 1.0 / (1000.0 * samplingrate() ); //return the duration of one pcm sample
  }

  if (layer()==I) {
    return frameDur / 12.0; //there is one granule of 12 samples
  } else if (layer()==II || (layer()==III && res == LOW)) {
    return frameDur / 36.0; // three granules of 12 samples each
  } else { // layer==III HIGH res
    return frameDur/((Layer3*)audio)->granules(); // one or  two granule(s) of 1 sample each.
  }
}


/*---------------- window function --------------------*/

CSAPI_MPEG bool
MPEGfile::seek_window( long w_nb ) {
  int nb_gr = nb_granules();
  // frame no to stop
  long stopframe = w_nb / (long) nb_gr;
  // update current granule number after seeking
  gr_current = (w_nb == 0) ? -1 : (w_nb - 1) % nb_gr;

  if ( w_nb < windowNo ) {
    // position file pointer at beginning
    rewind(fd);
    frameNo = 0;
    bitsread = 0;
    analysed = false;
  }

  // skip frames until specified frame is reached
  while ( frameNo < stopframe ) {
    if (!skip_frame()) {
      windowNo = frameNo * nb_gr;
      return false;
    }
    analysed = false;
  }

  windowNo = w_nb;
  return true;
}

CSAPI_MPEG unsigned int
MPEGfile::timeticks( Resolution res ) {
  if ( layer() == III  ) {
    if ( res == LOW || res == PCM) {
      return 18;
    } else {
      return 1;
    }
  } else {
    return 12;
  }

}


/*------------------- skip and analyse function -----------*/

CSAPI_MPEG bool
MPEGfile::next_window( Resolution res ) {
  int nb_gr = nb_granules();
  DecodeLevel touse = dec_subbands;
  //future current window
  long act = windowNo;

  // matching resolution and decodelevel
  switch (res) {
  case NO:
    touse = dec_fields; break;
  case LOW:
    touse = dec_subbands; break;
  case HIGH:
    if ( layer() == III) {
      touse = dec_subsubbands;
    } else {
      touse = dec_subbands;
    }; break;
  case PCM:
    touse = dec_pcm; break;
  default:
    break;
  }

  // also works for gr_current == -1, at the begining
  if ( gr_current < (nb_gr - 1)) {
    //that is not the last granule of the current frame

    if ( analysed && touse < decoded ) {
      //the current frame has been analysed before, but with a wrong resolution
      //so we come back to the current window, but without analysis
      windowNo++;
      seek_window (act);
    }

    if ( !analysed || touse < decoded ) {
      //the current window is not in the current frame!
      //because no analyse has been done
      //so just analyse the next frame with the right decodeLevel
      if (!parse_frame(touse))
	return false;
      //now the current window is in the current frame
      decoded = touse;
      analysed = true;
    }
    //just go to the next granule to go the next window
    gr_current++;

  } else {
    //last granule of a frame

    if ( !analysed ) {
      //the current window is not in the current frame!
      //because no analyse has been done
      //so must skip the frame containing the current window
      //before parsing the next one
      if (!skip_frame())
	return false;
    }

    //now parse the next frame, the next window will be granule 0 of that frame
    if (!parse_frame(touse))
      return false;
    decoded = touse;
    analysed = true;
    gr_current = 0;
  }

  windowNo++;
  return true;
}

CSAPI_MPEG bool
MPEGfile::skip_window(){
  int nb_gr = nb_granules();

 // also works for gr_current == -1, at the begining
  if ( gr_current < (nb_gr - 1) ) {
    //that is not the last granule of the current frame
    gr_current++;

  } else {
    //last granule of a frame

    if (!data_available()) return false;
    if ( (windowNo / nb_gr) > frameNo) {
      //that means that the current window is not in the current frame because
      //of skipping windows
      if (!skip_frame())
	return false;
      if (!data_available())
	return false;
      //means this is the end of the file
    }
    //new window won`t be in the current frame,
    //but in the next frame at granule 0
    gr_current = 0;
    analysed = false;
  }

  windowNo++;
  return true;
}


/*------------- access function ----------------*/

CSAPI_MPEG double
MPEGfile::freq_value( unsigned int ch, unsigned int sb, unsigned int nb = 0,
		      Resolution res) {
  // I don't believe this was correct...
  // ...but it works
  if ( res == HIGH && layer() == III) {
    return mdct_sample (ch,sb); //576 subbands
  } else {
    return restored_sample (ch,sb,nb); // 32 subbands
  }
  /* This might be correct, but it doesn't work well

  if (layer() != III) {
    return restored_sample (ch, sb, nb); // 32 subbands
  }
  // layer III needs extra treatment
  if (res == HIGH) {
    int subb = sb/SSLIMIT;
    int ss   = sb%SSLIMIT;
    return restored_sample(ch,subb,ss); //576 subbands
  } else {
    return mdct_sample(ch,sb,nb); //32 subbands in 18 windows
  }
  */

}

CSAPI_MPEG unsigned int
MPEGfile::nb_subbands( Resolution res ) {
  if ( layer() == III && res == HIGH ) {
    return 576;
  } else {
    return 32;
  }

}


/*--------------- pcm decoder --------------------*/
// returns number of samples in buffer
CSAPI_MPEG long
MPEGfile::decode (short *buffer, long window, Channels ch) {
  // check space in buffer
  if (buffer == NULL) {
    return -1;
  }

  // check channels requested
  if ( ch != LEFT && channels()==1) {
    cerr << "MaaateMPEG: wrong channel to be decoded, will decode LEFT channel." << endl;
    ch = LEFT;
  }

  //number of samples in buffer
  long samps = 0;

  int bd,sub,gr,tot;
  int nb_g;
  long act_win, act_w;

  switch (layer()) {
  case I:
    // from one window to another
    for (act_win = 0; act_win < window; act_win++ )  {
      if (!next_window(PCM)) break;
      // from one sample to another
      for (int bandsample = 0; bandsample < 12; bandsample++) {
	// from one subband to another
	for (int subband = 0; subband < SBLIMIT; subband++) {
	  if (ch != RIGHT) {
	    buffer[samps++] = pcm_sample(0, subband,
					 bandsample,
					 gr_current);
	  }
	  if (ch != LEFT) {
	    buffer[samps++] = pcm_sample(1, subband,
					 bandsample,
					 gr_current);
	  }
	}
      }
    }
    break;

  case II:
    // from one window to another
    for (act_win = 0; act_win < window; act_win++ )  {
      if (!next_window(PCM)) break;
      // from one sample to another
      for (int bandsample = 0; bandsample < 12; bandsample++) {
	// from one subband to another
	for (int subband = 0; subband < SBLIMIT; subband++) {
	  if (ch != RIGHT) {
	    //special mapping because layer II has a special way to
	    //store the pcm samples
	    tot = subband + bandsample * SBLIMIT + gr_current * 384;
	    bd = tot / 96;
	    sub = tot % 96;
	    gr = sub / SBLIMIT;
	    sub = sub % SBLIMIT;
	    buffer[samps++] = pcm_sample(0, sub,
					 bd,
					 gr);
	  }
	  if (ch != LEFT) {
	    //special mapping because layer II has a special way to
	    //store the pcm samples
	    tot = subband + bandsample * SBLIMIT + gr_current * 384;
	    bd = tot / 96;
	    sub = tot % 96;
	    gr = sub / SBLIMIT;
	    sub = sub % SBLIMIT;
	    buffer[samps++] = pcm_sample(1, sub,
					 bd,
					 gr);
	  }
	}
      }
    }
    break;

  case III:
    nb_g = nb_granules() - 1;
    act_w = 0;
    while (act_w < window)  {
      if (!next_window(PCM)) break;

      // from one sample to another
      for (int bandsample = 0; bandsample < 18; bandsample++) {
	// from one subband to another
	for (int subband = 0; subband < SBLIMIT; subband++) {
	  if (ch != RIGHT) {
	    buffer[samps++] = pcm_sample(0, gr_current,
					 subband,
					 bandsample);
	  }
	  if (ch != LEFT) {
	    buffer[samps++] = pcm_sample(1, gr_current,
					 subband,
					 bandsample);
	  }
	}
      }
      act_w++;
    }
   break;
  default: break;
  }
  return samps;
}


/*------------ MPEG specific functions ---------------------------*/

//return gr_current
CSAPI_MPEG int
MPEGfile::selected_granule() {
  return gr_current;
}

//return frameNo
CSAPI_MPEG long
MPEGfile::frame() {
  return frameNo;
}

//allow to parse next frame if available, keep windowNo up to date
CSAPI_MPEG bool
MPEGfile::goTo_nextFrame( Resolution res) {
  if (!data_available()) return false;
  long oldfr = frameNo;
  while (frameNo == oldfr) {
    if (!next_window(res))
      return false;
  }
  return true;
}


// returns whether end of stream was/will be reached
CSAPI_MPEG bool
MPEGfile::data_available() {
  if (!(fd))
    return false;
  static struct stat *buf = (struct stat *) malloc (sizeof(struct stat));
  stat(filename.c_str(), buf);
  if (((long)buf->st_size - ftell(fd)) < 5)
    return false;
  //fileDuration = windowNo;
  return true;
}

// reads and checks the header of a frame
CSAPI_MPEG bool
MPEGfile::parse_header() {

#define MAXSEARCH 2048
  // read 4 bytes into header bitfield
  register unsigned short buf=0;

  // read over initial junk to find header; give up after 2048 bytes
  int i=-2;

  while (((buf & 0xfff0) != 0xfff0) && (i<MAXSEARCH)) {
    if ((buf & 0x00ff) == 0x00ff) {
      // only need to read next byte to try and get sync word
      register unsigned char buf2=0;
      if (fread(&buf2, sizeof (unsigned char), 1, fd) != 1) {
	return false;
      }
      buf = (buf << 8) | buf2;
      i++;
    } else {
      // read next 4 bytes
      if (fread(&buf, sizeof (unsigned short), 1, fd) != 1) {
	return false;
      }
      i+=2;
#ifndef WORDS_BIGENDIAN
      // exchange the two bytes because of wrong byteorder
      buf = (buf << 8) | (buf >> 8);
#endif
    }
  }
  if (i>0) {
    if (i==MAXSEARCH) {
      cerr << "MaaateP: Gave up searching valid MPEG header after "
	   << MAXSEARCH << " bytes" << endl;
      return false;
    }
    cerr << "MaaateP: Skipped " << i
	 << " byte(s) to find valid MPEG header at file position "
	 << ftell(fd)
	 << endl;
  }

  // write first two bytes to header
#ifndef WORDS_BIGENDIAN
  header.sync            = (buf >> 4) & 0xFFF;
  header.version         = (buf >> 3) & 0x1;
  header.layer           = (buf >> 1) & 0x3;
  header.errorprotection = buf & 0x1;
#else
  ((unsigned short*) (&header))[0] = buf;
#endif

  if (fread(&buf, sizeof (unsigned short), 1, fd) != 1) {
    return false;
  }
#ifndef WORDS_BIGENDIAN
  // exchange the two bytes because of wrong byteorder
  buf = (buf << 8) | (buf >> 8);
  // write last two bytes to header
  header.bitrate         = (buf >> 12) & 0xF;
  header.samplingrate    = (buf >> 10) & 0x3;
  header.padding         = (buf >> 9) & 0x1;
  header.extension       = (buf >> 8) & 0x1;
  header.mode            = (buf >> 6) & 0x3;
  header.mode_ext        = (buf >> 4) & 0x3;
  header.copyright       = (buf >> 3) & 0x1;
  header.original        = (buf >> 2) & 0x1;
  header.emphasis        = buf & 0x3;
#else
  // write last two bytes to header
  ((unsigned short*) (&header))[1] = buf;
#endif

  // update frame number
  frameNo++;

  // check header
  if (!checkheader()) {
    cerr << "MaaateP: Error parsing header of frame "
	 << frameNo           << " of file "
	 << filename.c_str()  << "." << endl;
    return false;
  }

  return true;
}


// reads the header of a frame, decides about the layer,
// creates a layer-object accordingly, reads the checksum (if required),
// and reads the data (via the layer-object)
CSAPI_MPEG bool
MPEGfile::parse_data(DecodeLevel decode) {

  // create layerspecific object
  if (!create_layer())
    return false;

  // read checksum
  if (!read_checksum())
    return false;

  // buffer data
  if (!buffer_data())
    return false;

  // parse buffered audio data via layer object
  if (!audio->parse_data(decode)) {
    cerr << "MaaateP: Error parsing audio data."<<endl;
    return false;
  }

  return true;
}


// reads the header of a frame, decides about the layer,
// creates a layer-object accordingly, reads the checksum (if required),
// and reads the data (via the layer-object)
CSAPI_MPEG bool
MPEGfile::parse_frame(DecodeLevel decode) {

  // calls parse_header
  if (!parse_header())
    return false;

  // calls parse_data
  if (!parse_data(decode))
    return false;


  return true;
}


// skips over the data of a frame by reading its data into an unused buffer
// doesn't parse the data (but: LAYER 3 should remember some!!! - MISSING!!!)
CSAPI_MPEG bool
MPEGfile::skip_data() {

  // create layerspecific object
  if (!create_layer())
    return false;

  // read checksum
  if (!read_checksum())
    return false;

  // buffer data
  if (!buffer_data())
    return false;

  if ( layer() == III) { //this is a way to fix the problem with buffering in layer III
    // parse buffered audio data via layer object
    if (!audio->parse_data(dec_fields)) {
      cerr << "MaaateP: Error parsing audio data."<<endl;
      return false;
    }
  }

  return true;
}


// skips over a frame by reading its haeder & data into an unused buffer
// doesn't parse the data (but: LAYER 3 should remember some!!! - MISSING!!!)
CSAPI_MPEG bool
MPEGfile::skip_frame() {

  // calls parse_header
  if (!parse_header())
    return false;

  // calls parse_data
  if (!skip_data())
    return false;


  return true;
}


// create layerspecific object (first time or when layer switiching occurs)
CSAPI_MPEG bool
MPEGfile::create_layer() {
  if (audio==0 || (layer() != lastlayer)) {
    if (audio != 0) delete audio;
    if (layer() == I) {
      audio = new Layer1(this);
    } else if (layer() == II) {
      audio = new Layer2(this);
    } else if (layer() == III) {
      audio = new Layer3(this);
    } else {
      cerr << "MaaateP: Unknown Layer, cannot create object. " << endl;
      return false;
    }
    lastlayer = layer();
  }
  return true;
}


// read checksum
CSAPI_MPEG bool
MPEGfile::read_checksum() {
  if (crcprotected()) {
    short chktmp;
    // read 2 bytes (=16bit) into checksum bitfield
    if (fread (&chktmp, sizeof (unsigned char), 2, fd) != 2) {
      cerr << "MaaateP: Error reading checksum." << endl;
      return false;
    }
    checksum = chktmp;
#ifndef WORDS_BIGENDIAN
    // exchange the two bytes because of wrong byteorder
    checksum = (checksum << 8) | (checksum >> 8);
#endif
  }
  return true;
}


// read audio data into buffer
CSAPI_MPEG bool
MPEGfile::buffer_data() {
  bitsread=0;
  unsigned int nobytes = framesize();
  if (fread((char*)buffer, sizeof(unsigned char), nobytes, fd) != nobytes) {
    if (feof(fd)) { // end of file
      //	    cerr << "MaaateP: WARNING: End of file reached." << endl;
    } else {
      cerr << "MaaateP: Error buffering stream." << endl;
      return false;
    }
  }
#ifndef WORDS_BIGENDIAN
  // swap the bytes
  for (unsigned int i=0; i < ((nobytes/4)+1); i++) {
    swap_int((unsigned char *) &(buffer[i]));
  }
#endif
  return true;
}


/*------------- layer-specific access to audio data -------------------*/
CSAPI_MPEG int
MPEGfile::bitallocation (unsigned int ch, unsigned int sb) {
  if (layer()==III) {
    cerr << "MaaateP: Layer 3 has no bitallocation scheme\n";
    return 0;
  } else {
    return audio->bitallocation(ch, sb);
  }
}

CSAPI_MPEG int
MPEGfile::scfsi (unsigned int ch, unsigned int sb) {
  if (layer()==I) {
    cerr << "MaaateP: Layer 1 has no scale factor selection information\n";
    return 0;
  } else {
    return audio->scfsi(ch, sb);
  }
}

CSAPI_MPEG float
MPEGfile::scalefactor (unsigned int ch, unsigned int sb) {
  return audio->scalefactor(ch, sb, gr_current);
}

CSAPI_MPEG int
MPEGfile::sample (unsigned int ch, unsigned int sb, unsigned int no) {
  return audio->sample(ch, sb, no, gr_current);
}

CSAPI_MPEG double
MPEGfile::restored_sample (unsigned int ch, unsigned int sb, unsigned int no) {
  return audio->restored_sample(ch, sb, no, gr_current);
}

CSAPI_MPEG short
MPEGfile::pcm_sample (unsigned int ch, unsigned int sb, unsigned int no, unsigned int ss) {
  return audio->pcm_sample(ch, sb, no, ss);
}

/* get a pcm sample of the current frame
   this does not continue reading to a requested position*/
CSAPI_MPEG short
MPEGfile::pcm (unsigned int ch, unsigned int number) {
  // make sure it's in the current frame
  if (number > samples_per_frame()) {
    number = samples_per_frame();
  }

  // XXX: THIS IS UNTESTED!
  // calculate sb, no and ss from number
  unsigned int sb = 0 , gr = 0, ss = 0;
  if (layer() == I) {
    gr = 0;
    sb = number % 32;
    ss = number / 32;
  }
  if (layer() == II) {
    sb = number % 32;
    gr = (number / 32 ) % 2;
    ss = (number / 32 ) / 2;
  }
  if (layer() == III) { //TESTED
    ss = number % 32;
    gr = (number / 32) % 18;
    sb = (number / 32) / 18;
  }
  return audio->pcm_sample(ch, sb, ss, gr);
}

CSAPI_MPEG double
MPEGfile::mdct_sample (unsigned int ch, unsigned int ssb) {
  if (layer() == III) {
    return ((Layer3*) audio)->mdct_sample(ch, gr_current, ssb);
  } else {
    cerr << "MaaateP: Only Layer 3 has mdct_sample information\n";
    return 0.0;
  }
}

CSAPI_MPEG void
MPEGfile::printSideinfo () {
  if (layer() != III) {
    cerr << "MaaateP: Side information not available for Layer"
	 << layer()+1 << "." << endl;
    cerr << "Only Layer III has a side information header." << endl;
  } else {
    ((Layer3*) audio)->printSideinfo();
  }
}

CSAPI_MPEG unsigned int
MPEGfile::part2_3_length (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has part2_3_length information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->part2_3_length(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::big_values (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has big_values information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->big_values(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::count1_values (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has count1_values information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->count1_values(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::global_gain (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has global_gain information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->global_gain(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::scalefac_compress (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has scalefac_compress information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->scalefac_compress(ch,gr_current);
  }
}

CSAPI_MPEG bool
MPEGfile::window_switching (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has window_switching information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->window_switching(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::blocktype (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has blocktype information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->blocktype(ch,gr_current);
  }
}

CSAPI_MPEG bool
MPEGfile::mixedblock (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has mixedblock information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->mixedblock(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::table_select (unsigned int ch, unsigned int area) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has table_select information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->table_select(ch,gr_current, area);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::subblock_gain (unsigned int ch, unsigned int area) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has subblock_gain information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->subblock_gain(ch,gr_current, area);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::region0_samps (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has region0_samps information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->region0_samps(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::region1_samps (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has region1_samps information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->region1_samps(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::region2_samps (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has region2_samps information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->region2_samps(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::preflag (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has preflag information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->preflag(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::scalefac_scale (unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has scalefac_scale information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->scalefac_scale(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::count1table_select(unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has count1table_select information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->count1table_select(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::scf_band_bound_l(unsigned int subbandindex) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has scf_band_bound_l information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->scf_band_bound_l(subbandindex);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::scf_band_bound_s(unsigned int subbandindex) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has scf_band_bound_s information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->scf_band_bound_s(subbandindex);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::slen1(unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has slen1 information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->slen1(ch,gr_current);
  }
}

CSAPI_MPEG unsigned int
MPEGfile::slen2(unsigned int ch) {
  if (layer()!=III) {
    cerr << "MaaateP: Only Layer 3 has slen2 information\n";
    return 0;
  } else {
    return ((Layer3*) audio)->slen2(ch,gr_current);
  }
}


// returns to the layer-specific parser the number of requested bits
// from the audio file
CSAPI_MPEG unsigned int
MPEGfile::readbitsfrombuffer(unsigned int nobits) {
  static unsigned int bitmask[33] = {
    0,  // dummy
    0x00000001, 0x00000003, 0x00000007, 0x0000000F,
    0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF,
    0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF,
    0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF,
    0x0001FFFF, 0x0003FFFF, 0x0007FFFF, 0x000FFFFF,
    0x001FFFFF, 0x003FFFFF, 0x007FFFFF, 0x00FFFFFF,
    0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF,
    0x1FFFFFFF, 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF
  };

  unsigned int val = 0; // resulting value
  unsigned int bufferindex = bitsread / 32; // index of current word
  unsigned int whichbit = bitsread % 32;    // current bitnumber within word
  unsigned int intlength = whichbit+nobits; // last bit to be read
  bitsread += nobits; // remember until where read

  if (nobits > 32 || bufferindex>=MAX_BUFSIZE) {
    cerr << "MaaateP: Error reading from bitstream ("
	 << nobits << "," << bufferindex << ")" << endl;
    return 0;
  }

  if (intlength <= 32)  {
    // all bits contained in buffer[bufferindex]
    val = (buffer[bufferindex] >> (32 - intlength)) & bitmask[nobits];
  } else {
    // bits are in buffer[bufferindex] and buffer[bufferindex+1]
    unsigned int fromfirst = 32-whichbit;
    unsigned int fromsec   = intlength-32;
    val = (buffer[bufferindex] & bitmask[fromfirst]) << fromsec;
    val |= (buffer[bufferindex+1] >> (32-fromsec)) & bitmask[fromsec];
  }

  return val;
}

CSAPI_MPEG int
MPEGfile::nb_granules() {
 if (layer()==I) {
    return 1;
  } else if (layer()==II) {
    return 3; // three granules
  } else { // layer==III HIGH res
    return ((Layer3*)audio)->granules();
  }
}