header.java

java编写的mp3播放器

	 */
	public int vbr_scale() { return h_vbr_scale; }

	/**
	 * Return VBR TOC.
	 * @return vbr toc ot null if not available
	 */
	public byte[] vbr_toc() { return h_vbr_toc; }

	/**
	 * Returns Checksum flag.
	 * Compares computed checksum with stream checksum.
	 */
	public boolean checksum_ok () { return (checksum == crc.checksum()); }

	// Seeking and layer III stuff
	/**
	 * Returns Layer III Padding bit.
	 */
	public boolean padding()
	{
		if (h_padding_bit == 0) return false;
	  else return true;
	}

	/**
	 * Returns Slots.
	 */
	public int slots() { return nSlots; }

	/**
	 * Returns Mode Extension.
	 */
	public int mode_extension() { return h_mode_extension; }

	// E.B -> private to public
	public static final int bitrates[][][] = {
		{{0 /*free format*/, 32000, 48000, 56000, 64000, 80000, 96000,
	  112000, 128000, 144000, 160000, 176000, 192000 ,224000, 256000, 0},
	 	{0 /*free format*/, 8000, 16000, 24000, 32000, 40000, 48000,
	  56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000, 0},
	 	{0 /*free format*/, 8000, 16000, 24000, 32000, 40000, 48000,
	  56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000, 0}},

		{{0 /*free format*/, 32000, 64000, 96000, 128000, 160000, 192000,
	   224000, 256000, 288000, 320000, 352000, 384000, 416000, 448000, 0},
	  {0 /*free format*/, 32000, 48000, 56000, 64000, 80000, 96000,
	   112000, 128000, 160000, 192000, 224000, 256000, 320000, 384000, 0},
	  {0 /*free format*/, 32000, 40000, 48000, 56000, 64000, 80000,
	   96000, 112000, 128000, 160000, 192000, 224000, 256000, 320000, 0}},
		// SZD: MPEG2.5
		{{0 /*free format*/, 32000, 48000, 56000, 64000, 80000, 96000,
	  112000, 128000, 144000, 160000, 176000, 192000 ,224000, 256000, 0},
	 	{0 /*free format*/, 8000, 16000, 24000, 32000, 40000, 48000,
	  56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000, 0},
	 	{0 /*free format*/, 8000, 16000, 24000, 32000, 40000, 48000,
	  56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000, 0}},

		};

	// E.B -> private to public
	/**
	 * Calculate Frame size.
	 * Calculates framesize in bytes excluding header size.
	 */
	public int calculate_framesize()
	{

	 if (h_layer == 1)
	 {
	   framesize = (12 * bitrates[h_version][0][h_bitrate_index]) /
	               frequencies[h_version][h_sample_frequency];
	   if (h_padding_bit != 0 ) framesize++;
	   framesize <<= 2;		// one slot is 4 bytes long
	   nSlots = 0;
	 }
	 else
	 {
	   framesize = (144 * bitrates[h_version][h_layer - 1][h_bitrate_index]) /
	               frequencies[h_version][h_sample_frequency];
	   if (h_version == MPEG2_LSF || h_version == MPEG25_LSF) framesize >>= 1;	// SZD
	   if (h_padding_bit != 0) framesize++;
	   // Layer III slots
	   if (h_layer == 3)
	   {
	     if (h_version == MPEG1)
	     {
	  		 nSlots = framesize - ((h_mode == SINGLE_CHANNEL) ? 17 : 32) // side info size
	  								  -  ((h_protection_bit!=0) ? 0 : 2) 		       // CRC size
	  								  - 4; 								             // header size
	     }
	     else
		 {  // MPEG-2 LSF, SZD: MPEG-2.5 LSF
	        nSlots = framesize - ((h_mode == SINGLE_CHANNEL) ?  9 : 17) // side info size
	  					   		  -  ((h_protection_bit!=0) ? 0 : 2) 		       // CRC size
	  								  - 4; 								             // header size
	     }
	   }
	   else
	   {
	  	 nSlots = 0;
	   }
	 }
	 framesize -= 4;             // subtract header size
	 return framesize;
	}

	/**
	 * Returns the maximum number of frames in the stream.
	 * @param streamsize
	 * @return number of frames
	 */
	public int max_number_of_frames(int streamsize)  // E.B
	{
		if (h_vbr == true) return h_vbr_frames;
		else
		{
			if ((framesize + 4 - h_padding_bit) == 0) return 0;
			else return(streamsize / (framesize + 4 - h_padding_bit));
		}
	}

	/**
	 * Returns the maximum number of frames in the stream.
	 * @param streamsize
	 * @return number of frames
	 */
	public int min_number_of_frames(int streamsize) // E.B
	{
		if (h_vbr == true) return h_vbr_frames;
		else
		{
	  		if ((framesize + 5 - h_padding_bit) == 0) return 0;
	  		else return(streamsize / (framesize + 5 - h_padding_bit));
		}
	}


	/**
	 * Returns ms/frame.
	 * @return milliseconds per frame
	 */
	public float ms_per_frame() // E.B
	{
		if (h_vbr == true)
		{			
			double tpf = h_vbr_time_per_frame[layer()] / frequency();
			if ((h_version == MPEG2_LSF) || (h_version == MPEG25_LSF)) tpf /= 2;
			return ((float) (tpf * 1000));
		}
		else
		{
			float ms_per_frame_array[][] = {{8.707483f,  8.0f, 12.0f},
											{26.12245f, 24.0f, 36.0f},
											{26.12245f, 24.0f, 36.0f}};
			return(ms_per_frame_array[h_layer-1][h_sample_frequency]);
		}
	}

	/**
	 * Returns total ms.
	 * @param streamsize
	 * @return total milliseconds
	 */
	public float total_ms(int streamsize) // E.B
	{
		return(max_number_of_frames(streamsize) * ms_per_frame());
	}

	/**
	 * Returns synchronized header.
	 */
	public int getSyncHeader() // E.B
	{
		return _headerstring;
	}

	// functions which return header informations as strings:
	/**
	 * Return Layer version.
	 */
	public String layer_string()
	{
		switch (h_layer)
		{
	   case 1:
	  	return "I";
	   case 2:
	  	return "II";
	   case 3:
	  	return "III";
		}
	  return null;
	}

	// E.B -> private to public
	public static final String bitrate_str[][][] = {
		{{"free format", "32 kbit/s", "48 kbit/s", "56 kbit/s", "64 kbit/s",
	  "80 kbit/s", "96 kbit/s", "112 kbit/s", "128 kbit/s", "144 kbit/s",
	  "160 kbit/s", "176 kbit/s", "192 kbit/s", "224 kbit/s", "256 kbit/s",
	  "forbidden"},
	  {"free format", "8 kbit/s", "16 kbit/s", "24 kbit/s", "32 kbit/s",
	  "40 kbit/s", "48 kbit/s", "56 kbit/s", "64 kbit/s", "80 kbit/s",
	  "96 kbit/s", "112 kbit/s", "128 kbit/s", "144 kbit/s", "160 kbit/s",
	  "forbidden"},
	  {"free format", "8 kbit/s", "16 kbit/s", "24 kbit/s", "32 kbit/s",
	  "40 kbit/s", "48 kbit/s", "56 kbit/s", "64 kbit/s", "80 kbit/s",
	  "96 kbit/s", "112 kbit/s", "128 kbit/s", "144 kbit/s", "160 kbit/s",
	  "forbidden"}},

	  {{"free format", "32 kbit/s", "64 kbit/s", "96 kbit/s", "128 kbit/s",
	  "160 kbit/s", "192 kbit/s", "224 kbit/s", "256 kbit/s", "288 kbit/s",
	  "320 kbit/s", "352 kbit/s", "384 kbit/s", "416 kbit/s", "448 kbit/s",
	  "forbidden"},
	  {"free format", "32 kbit/s", "48 kbit/s", "56 kbit/s", "64 kbit/s",
	  "80 kbit/s", "96 kbit/s", "112 kbit/s", "128 kbit/s", "160 kbit/s",
	  "192 kbit/s", "224 kbit/s", "256 kbit/s", "320 kbit/s", "384 kbit/s",
	  "forbidden"},
	  {"free format", "32 kbit/s", "40 kbit/s", "48 kbit/s", "56 kbit/s",
	  "64 kbit/s", "80 kbit/s" , "96 kbit/s", "112 kbit/s", "128 kbit/s",
	  "160 kbit/s", "192 kbit/s", "224 kbit/s", "256 kbit/s", "320 kbit/s",
	  "forbidden"}},
		// SZD: MPEG2.5
		{{"free format", "32 kbit/s", "48 kbit/s", "56 kbit/s", "64 kbit/s",
	  "80 kbit/s", "96 kbit/s", "112 kbit/s", "128 kbit/s", "144 kbit/s",
	  "160 kbit/s", "176 kbit/s", "192 kbit/s", "224 kbit/s", "256 kbit/s",
	  "forbidden"},
	  {"free format", "8 kbit/s", "16 kbit/s", "24 kbit/s", "32 kbit/s",
	  "40 kbit/s", "48 kbit/s", "56 kbit/s", "64 kbit/s", "80 kbit/s",
	  "96 kbit/s", "112 kbit/s", "128 kbit/s", "144 kbit/s", "160 kbit/s",
	  "forbidden"},
	  {"free format", "8 kbit/s", "16 kbit/s", "24 kbit/s", "32 kbit/s",
	  "40 kbit/s", "48 kbit/s", "56 kbit/s", "64 kbit/s", "80 kbit/s",
	  "96 kbit/s", "112 kbit/s", "128 kbit/s", "144 kbit/s", "160 kbit/s",
	  "forbidden"}},
	  };

	/**
	 * Return Bitrate.
	 * @return bitrate in bps
	 */
	public String bitrate_string()
	{
		if (h_vbr == true)
		{
			return Integer.toString(bitrate()/1000)+" kb/s";		
		}
	  else return bitrate_str[h_version][h_layer - 1][h_bitrate_index];
	}

	/**
	 * Return Bitrate.
	 * @return bitrate in bps and average bitrate for VBR header
	 */
	public int bitrate()
	{
		if (h_vbr == true)
		{
			return ((int) ((h_vbr_bytes * 8) / (ms_per_frame() * h_vbr_frames)))*1000;		
		}
		else return bitrates[h_version][h_layer - 1][h_bitrate_index];
	}

	/**
	 * Return Instant Bitrate.
	 * Bitrate for VBR is not constant.
	 * @return bitrate in bps
	 */
	public int bitrate_instant()
	{
		return bitrates[h_version][h_layer - 1][h_bitrate_index];
	}

	/**
	 * Returns Frequency
	 * @return frequency string in kHz
	 */
	public String sample_frequency_string()
	{
		switch (h_sample_frequency)
		{
	    case THIRTYTWO:
	  	if (h_version == MPEG1)
	  		return "32 kHz";
	  	else if (h_version == MPEG2_LSF)
	    	return "16 kHz";
	    else	// SZD
	    	return "8 kHz";
	    case FOURTYFOUR_POINT_ONE:
	  	if (h_version == MPEG1)
	  		return "44.1 kHz";
	  	else if (h_version == MPEG2_LSF)
	    	return "22.05 kHz";
		else	// SZD
	    	return "11.025 kHz";
	    case FOURTYEIGHT:
	  	if (h_version == MPEG1)
	  		return "48 kHz";
	  	else if (h_version == MPEG2_LSF)
	    	return "24 kHz";
		else	// SZD
			return "12 kHz";
	  }
	  return(null);
	}

	/**
	 * Returns Mode.
	 */
	public String mode_string()
	{
	   switch (h_mode)
	   {
	     case STEREO:
	  	return "Stereo";
	     case JOINT_STEREO:
	  	return "Joint stereo";
	     case DUAL_CHANNEL:
	  	return "Dual channel";
	     case SINGLE_CHANNEL:
	  	return "Single channel";
	   }
	   return null;
	}

	/**
	 * Returns Version.
	 * @return MPEG-1 or MPEG-2 LSF or MPEG-2.5 LSF
	 */
	public String version_string()
	{
	  switch (h_version)
	  {
	    case MPEG1:
	      return "MPEG-1";
	    case MPEG2_LSF:
	      return "MPEG-2 LSF";
	    case MPEG25_LSF:	// SZD
	      return "MPEG-2.5 LSF";
	  }
	  return(null);
	}

	/**
	 * Returns the number of subbands in the current frame.
	 * @return number of subbands
	 */
	public int number_of_subbands() {return h_number_of_subbands;}

	/**
	 * Returns Intensity Stereo.
	 * (Layer II joint stereo only).
	 * Returns the number of subbands which are in stereo mode,
	 * subbands above that limit are in intensity stereo mode.
	 * @return intensity
	 */
	public int intensity_stereo_bound() {return h_intensity_stereo_bound;}
}