mp3.c

flash swf file player

/*
    Ming, an SWF output library
    Copyright (C) 2002  Opaque Industries - http://www.opaque.net/

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/* $Id: mp3.c,v 1.10 2003/11/08 18:24:57 whamann Exp $ */

#include "libming.h"
#include "input.h"


#define MP3_FRAME_SYNC			 0xFFE00000

#define MP3_VERSION					 0x00180000
#define MP3_VERSION_25			 0x00000000
#define MP3_VERSION_RESERVED 0x00080000
#define MP3_VERSION_2				 0x00100000
#define MP3_VERSION_1				 0x00180000

#define MP3_LAYER						 0x00060000
#define MP3_LAYER_RESERVED	 0x00000000
#define MP3_LAYER_3					 0x00020000
#define MP3_LAYER_2					 0x00040000
#define MP3_LAYER_1					 0x00060000

#define MP3_PROTECT					 0x00010000 /* 16-bit CRC after header */

#define MP3_BITRATE					 0x0000F000
#define MP3_BITRATE_SHIFT		 12

int mp1l1_bitrate_table[] = { 0,	 32,	 64,	96, 128, 160, 192, 224,
						256, 288, 320, 352, 382, 416, 448 };

int mp1l2_bitrate_table[] = { 0,	 32,	 48,	56,	 64,	80,	 96, 112,
						128, 160, 192, 224, 256, 320, 384 };

int mp1l3_bitrate_table[] = { 0,		32,	 40,	48,	 56,	64,	 80,	96,
						112, 128, 160, 192, 224, 256, 320 };

int mp2l1_bitrate_table[] = { 0,		32,	 48,	56,	 64,	80,	 96, 112,
						128, 144, 160, 176, 192, 224, 256 };

int mp2l23_bitrate_table[] = { 0,		 8,	 16,	24,	 32,	40,	 48,	56,
						 64,	80,	 96, 112, 128, 144, 160 };

#define MP3_SAMPLERATE			 0x00000C00
#define MP3_SAMPLERATE_SHIFT 10

int mp1_samplerate_table[] = { 44100, 48000, 32000 };
int mp2_samplerate_table[] = { 22050, 24000, 16000 }; /* is this right?? */
int mp25_samplerate_table[] = { 11025, 12000, 8000 }; /* less samples in > versions? */

#define MP3_PADDING					 0x00000200 /* if set, add an extra slot - 4 bytes
						 for layer 1, 1 byte for 2+3 */

#define MP3_CHANNEL					 0x000000C0
#define MP3_CHANNEL_STEREO	 0x00000000
#define MP3_CHANNEL_JOINT		 0x00000040
#define MP3_CHANNEL_DUAL		 0x00000080
#define MP3_CHANNEL_MONO		 0x000000C0

/* rest of the header info doesn't affect frame size.. */

int nextMP3Frame(SWFInput input)
{
	unsigned long flags;
	int frameLen;
	int bitrate, bitrate_idx, samplerate, samplerate_idx;
	int version, layer, padding;

	/* get 4-byte header, bigendian */

	flags = SWFInput_getUInt32_BE(input);

	if(SWFInput_eof(input))
		return 0;

	if((flags & MP3_FRAME_SYNC) != MP3_FRAME_SYNC)
		return -1;

	bitrate_idx = (flags & MP3_BITRATE) >> MP3_BITRATE_SHIFT;
	samplerate_idx = (flags & MP3_SAMPLERATE) >> MP3_SAMPLERATE_SHIFT;

	switch(flags & MP3_VERSION)
	{
		case MP3_VERSION_1:	 version = 1; break;
		case MP3_VERSION_2:	 version = 2; break;
		case MP3_VERSION_25: version = 25; break;
		default: return -1;
	}
	switch(flags & MP3_LAYER)
	{
		case MP3_LAYER_1: layer = 1; break;
		case MP3_LAYER_2: layer = 2; break;
		case MP3_LAYER_3: layer = 3; break;
		default: return -1;
	}

	if(version == 1)
	{
		samplerate = mp1_samplerate_table[samplerate_idx];

		if(layer == 1)
			bitrate = mp1l1_bitrate_table[bitrate_idx];

		else if(layer == 2)
			bitrate = mp1l2_bitrate_table[bitrate_idx];

		else if(layer == 3)
			bitrate = mp1l3_bitrate_table[bitrate_idx];
	}
	else
	{
		if(version == 2)
			samplerate = mp2_samplerate_table[samplerate_idx];
		else
			samplerate = mp25_samplerate_table[samplerate_idx];

		if(layer == 1)
			bitrate = mp2l1_bitrate_table[bitrate_idx];
		else
			bitrate = mp2l23_bitrate_table[bitrate_idx];
	}

	padding = (flags & MP3_PADDING) ? 1 : 0;

	if(layer == 1)
		padding <<= 2;

	if(version == 1)
		frameLen = 144 * bitrate * 1000 / samplerate + padding;
	else
		frameLen = 72 * bitrate * 1000 / samplerate + padding;

	SWFInput_seek(input, frameLen-4, SEEK_CUR);

	return frameLen;
}


int getMP3Size(SWFInput input)
{
	return 0; // XXX
}


/*
 * Local variables:
 * tab-width: 2
 * c-basic-offset: 2
 * End:
 */