sbc.c

这是Linux环境下的蓝牙源代码

/*
 *
 *  Bluetooth low-complexity, subband codec (SBC) library
 *
 *  Copyright (C) 2004-2008  Marcel Holtmann <[e-mail]>
 *  Copyright (C) 2004-2005  Henryk Ploetz <[e-mail]>
 *  Copyright (C) 2005-2008  Brad Midgley <[e-mail]>
 *
 *
 *  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., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

/* todo items:

  use a log2 table for byte integer scale factors calculation (sum log2 results
  for high and low bytes) fill bitpool by 16 bits instead of one at a time in
  bits allocation/bitpool generation port to the dsp

*/

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

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>

#include "sbc_math.h"
#include "sbc_tables.h"

#include "sbc.h"

#define SBC_SYNCWORD	0x9C

/* This structure contains an unpacked SBC frame.
   Yes, there is probably quite some unused space herein */
struct sbc_frame {
	uint8_t frequency;
	uint8_t block_mode;
	uint8_t blocks;
	enum {
		MONO		= SBC_MODE_MONO,
		DUAL_CHANNEL	= SBC_MODE_DUAL_CHANNEL,
		STEREO		= SBC_MODE_STEREO,
		JOINT_STEREO	= SBC_MODE_JOINT_STEREO
	} mode;
	uint8_t channels;
	enum {
		LOUDNESS	= SBC_AM_LOUDNESS,
		SNR		= SBC_AM_SNR
	} allocation;
	uint8_t subband_mode;
	uint8_t subbands;
	uint8_t bitpool;
	uint8_t codesize;
	uint8_t length;

	/* bit number x set means joint stereo has been used in subband x */
	uint8_t joint;

	/* only the lower 4 bits of every element are to be used */
	uint8_t scale_factor[2][8];

	/* raw integer subband samples in the frame */

	int32_t sb_sample_f[16][2][8];
	int32_t sb_sample[16][2][8];	/* modified subband samples */
	int16_t pcm_sample[2][16*8];	/* original pcm audio samples */
};

struct sbc_decoder_state {
	int subbands;
	int32_t V[2][170];
	int offset[2][16];
};

struct sbc_encoder_state {
	int subbands;
	int position[2];
	int32_t X[2][160];
};

/*
 * Calculates the CRC-8 of the first len bits in data
 */
static const uint8_t crc_table[256] = {
	0x00, 0x1D, 0x3A, 0x27, 0x74, 0x69, 0x4E, 0x53,
	0xE8, 0xF5, 0xD2, 0xCF, 0x9C, 0x81, 0xA6, 0xBB,
	0xCD, 0xD0, 0xF7, 0xEA, 0xB9, 0xA4, 0x83, 0x9E,
	0x25, 0x38, 0x1F, 0x02, 0x51, 0x4C, 0x6B, 0x76,
	0x87, 0x9A, 0xBD, 0xA0, 0xF3, 0xEE, 0xC9, 0xD4,
	0x6F, 0x72, 0x55, 0x48, 0x1B, 0x06, 0x21, 0x3C,
	0x4A, 0x57, 0x70, 0x6D, 0x3E, 0x23, 0x04, 0x19,
	0xA2, 0xBF, 0x98, 0x85, 0xD6, 0xCB, 0xEC, 0xF1,
	0x13, 0x0E, 0x29, 0x34, 0x67, 0x7A, 0x5D, 0x40,
	0xFB, 0xE6, 0xC1, 0xDC, 0x8F, 0x92, 0xB5, 0xA8,
	0xDE, 0xC3, 0xE4, 0xF9, 0xAA, 0xB7, 0x90, 0x8D,
	0x36, 0x2B, 0x0C, 0x11, 0x42, 0x5F, 0x78, 0x65,
	0x94, 0x89, 0xAE, 0xB3, 0xE0, 0xFD, 0xDA, 0xC7,
	0x7C, 0x61, 0x46, 0x5B, 0x08, 0x15, 0x32, 0x2F,
	0x59, 0x44, 0x63, 0x7E, 0x2D, 0x30, 0x17, 0x0A,
	0xB1, 0xAC, 0x8B, 0x96, 0xC5, 0xD8, 0xFF, 0xE2,
	0x26, 0x3B, 0x1C, 0x01, 0x52, 0x4F, 0x68, 0x75,
	0xCE, 0xD3, 0xF4, 0xE9, 0xBA, 0xA7, 0x80, 0x9D,
	0xEB, 0xF6, 0xD1, 0xCC, 0x9F, 0x82, 0xA5, 0xB8,
	0x03, 0x1E, 0x39, 0x24, 0x77, 0x6A, 0x4D, 0x50,
	0xA1, 0xBC, 0x9B, 0x86, 0xD5, 0xC8, 0xEF, 0xF2,
	0x49, 0x54, 0x73, 0x6E, 0x3D, 0x20, 0x07, 0x1A,
	0x6C, 0x71, 0x56, 0x4B, 0x18, 0x05, 0x22, 0x3F,
	0x84, 0x99, 0xBE, 0xA3, 0xF0, 0xED, 0xCA, 0xD7,
	0x35, 0x28, 0x0F, 0x12, 0x41, 0x5C, 0x7B, 0x66,
	0xDD, 0xC0, 0xE7, 0xFA, 0xA9, 0xB4, 0x93, 0x8E,
	0xF8, 0xE5, 0xC2, 0xDF, 0x8C, 0x91, 0xB6, 0xAB,
	0x10, 0x0D, 0x2A, 0x37, 0x64, 0x79, 0x5E, 0x43,
	0xB2, 0xAF, 0x88, 0x95, 0xC6, 0xDB, 0xFC, 0xE1,
	0x5A, 0x47, 0x60, 0x7D, 0x2E, 0x33, 0x14, 0x09,
	0x7F, 0x62, 0x45, 0x58, 0x0B, 0x16, 0x31, 0x2C,
	0x97, 0x8A, 0xAD, 0xB0, 0xE3, 0xFE, 0xD9, 0xC4
};

static uint8_t sbc_crc8(const uint8_t *data, size_t len)
{
	uint8_t crc = 0x0f;
	size_t i;
	uint8_t octet;

	for (i = 0; i < len / 8; i++)
		crc = crc_table[crc ^ data[i]];

	octet = data[i];
	for (i = 0; i < len % 8; i++) {
		char bit = ((octet ^ crc) & 0x80) >> 7;

		crc = ((crc & 0x7f) << 1) ^ (bit ? 0x1d : 0);

		octet = octet << 1;
	}

	return crc;
}

/*
 * Code straight from the spec to calculate the bits array
 * Takes a pointer to the frame in question, a pointer to the bits array and
 * the sampling frequency (as 2 bit integer)
 */
static void sbc_calculate_bits(const struct sbc_frame *frame, int (*bits)[8])
{
	uint8_t sf = frame->frequency;

	if (frame->mode == MONO || frame->mode == DUAL_CHANNEL) {
		int bitneed[2][8], loudness, max_bitneed, bitcount, slicecount, bitslice;
		int ch, sb;

		for (ch = 0; ch < frame->channels; ch++) {
			max_bitneed = 0;
			if (frame->allocation == SNR) {
				for (sb = 0; sb < frame->subbands; sb++) {
					bitneed[ch][sb] = frame->scale_factor[ch][sb];
					if (bitneed[ch][sb] > max_bitneed)
						max_bitneed = bitneed[ch][sb];
				}
			} else {
				for (sb = 0; sb < frame->subbands; sb++) {
					if (frame->scale_factor[ch][sb] == 0)
						bitneed[ch][sb] = -5;
					else {
						if (frame->subbands == 4)
							loudness = frame->scale_factor[ch][sb] - sbc_offset4[sf][sb];
						else
							loudness = frame->scale_factor[ch][sb] - sbc_offset8[sf][sb];
						if (loudness > 0)
							bitneed[ch][sb] = loudness / 2;
						else
							bitneed[ch][sb] = loudness;
					}
					if (bitneed[ch][sb] > max_bitneed)
						max_bitneed = bitneed[ch][sb];
				}
			}

			bitcount = 0;
			slicecount = 0;
			bitslice = max_bitneed + 1;
			do {
				bitslice--;
				bitcount += slicecount;
				slicecount = 0;
				for (sb = 0; sb < frame->subbands; sb++) {
					if ((bitneed[ch][sb] > bitslice + 1) && (bitneed[ch][sb] < bitslice + 16))
						slicecount++;
					else if (bitneed[ch][sb] == bitslice + 1)
						slicecount += 2;
				}
			} while (bitcount + slicecount < frame->bitpool);

			if (bitcount + slicecount == frame->bitpool) {
				bitcount += slicecount;
				bitslice--;
			}

			for (sb = 0; sb < frame->subbands; sb++) {
				if (bitneed[ch][sb] < bitslice + 2)
					bits[ch][sb] = 0;
				else {
					bits[ch][sb] = bitneed[ch][sb] - bitslice;
					if (bits[ch][sb] > 16)
						bits[ch][sb] = 16;
				}
			}

			for (sb = 0; bitcount < frame->bitpool && sb < frame->subbands; sb++) {
				if ((bits[ch][sb] >= 2) && (bits[ch][sb] < 16)) {
					bits[ch][sb]++;
					bitcount++;
				} else if ((bitneed[ch][sb] == bitslice + 1) && (frame->bitpool > bitcount + 1)) {
					bits[ch][sb] = 2;
					bitcount += 2;
				}
			}

			for (sb = 0; bitcount < frame->bitpool && sb < frame->subbands; sb++) {
				if (bits[ch][sb] < 16) {
					bits[ch][sb]++;
					bitcount++;
				}
			}

		}

	} else if (frame->mode == STEREO || frame->mode == JOINT_STEREO) {
		int bitneed[2][8], loudness, max_bitneed, bitcount, slicecount, bitslice;
		int ch, sb;

		max_bitneed = 0;
		if (frame->allocation == SNR) {
			for (ch = 0; ch < 2; ch++) {
				for (sb = 0; sb < frame->subbands; sb++) {
					bitneed[ch][sb] = frame->scale_factor[ch][sb];
					if (bitneed[ch][sb] > max_bitneed)
						max_bitneed = bitneed[ch][sb];
				}
			}
		} else {
			for (ch = 0; ch < 2; ch++) {
				for (sb = 0; sb < frame->subbands; sb++) {
					if (frame->scale_factor[ch][sb] == 0)
						bitneed[ch][sb] = -5;
					else {
						if (frame->subbands == 4)
							loudness = frame->scale_factor[ch][sb] - sbc_offset4[sf][sb];
						else
							loudness = frame->scale_factor[ch][sb] - sbc_offset8[sf][sb];
						if (loudness > 0)
							bitneed[ch][sb] = loudness / 2;
						else
							bitneed[ch][sb] = loudness;
					}
					if (bitneed[ch][sb] > max_bitneed)
						max_bitneed = bitneed[ch][sb];
				}
			}
		}

		bitcount = 0;
		slicecount = 0;
		bitslice = max_bitneed + 1;
		do {
			bitslice--;
			bitcount += slicecount;
			slicecount = 0;
			for (ch = 0; ch < 2; ch++) {
				for (sb = 0; sb < frame->subbands; sb++) {
					if ((bitneed[ch][sb] > bitslice + 1) && (bitneed[ch][sb] < bitslice + 16))
						slicecount++;
					else if (bitneed[ch][sb] == bitslice + 1)
						slicecount += 2;
				}
			}
		} while (bitcount + slicecount < frame->bitpool);

		if (bitcount + slicecount == frame->bitpool) {
			bitcount += slicecount;
			bitslice--;
		}

		for (ch = 0; ch < 2; ch++) {
			for (sb = 0; sb < frame->subbands; sb++) {
				if (bitneed[ch][sb] < bitslice + 2) {
					bits[ch][sb] = 0;
				} else {
					bits[ch][sb] = bitneed[ch][sb] - bitslice;
					if (bits[ch][sb] > 16)
						bits[ch][sb] = 16;
				}
			}
		}

		ch = 0;
		sb = 0;
		while (bitcount < frame->bitpool) {
			if ((bits[ch][sb] >= 2) && (bits[ch][sb] < 16)) {
				bits[ch][sb]++;
				bitcount++;
			} else if ((bitneed[ch][sb] == bitslice + 1) && (frame->bitpool > bitcount + 1)) {
				bits[ch][sb] = 2;
				bitcount += 2;
			}
			if (ch == 1) {
				ch = 0;
				sb++;
				if (sb >= frame->subbands) break;
			} else
				ch = 1;
		}

		ch = 0;
		sb = 0;
		while (bitcount < frame->bitpool) {
			if (bits[ch][sb] < 16) {
				bits[ch][sb]++;
				bitcount++;
			}
			if (ch == 1) {
				ch = 0;
				sb++;
				if (sb >= frame->subbands) break;
			} else
				ch = 1;
		}

	}

}

/*
 * Unpacks a SBC frame at the beginning of the stream in data,
 * which has at most len bytes into frame.
 * Returns the length in bytes of the packed frame, or a negative
 * value on error. The error codes are:
 *
 *  -1   Data stream too short
 *  -2   Sync byte incorrect
 *  -3   CRC8 incorrect
 *  -4   Bitpool value out of bounds
 */
static int sbc_unpack_frame(const uint8_t *data, struct sbc_frame *frame,
				size_t len)
{
	int consumed;
	/* Will copy the parts of the header that are relevant to crc
	 * calculation here */
	uint8_t crc_header[11] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
	int crc_pos = 0;
	int32_t temp;

	int audio_sample;
	int ch, sb, blk, bit;	/* channel, subband, block and bit standard
				   counters */
	int bits[2][8];		/* bits distribution */
	uint32_t levels[2][8];	/* levels derived from that */

	if (len < 4)
		return -1;

	if (data[0] != SBC_SYNCWORD)
		return -2;

	frame->frequency = (data[1] >> 6) & 0x03;

	frame->block_mode = (data[1] >> 4) & 0x03;
	switch (frame->block_mode) {
	case SBC_BLK_4:
		frame->blocks = 4;
		break;
	case SBC_BLK_8:
		frame->blocks = 8;
		break;
	case SBC_BLK_12:
		frame->blocks = 12;
		break;
	case SBC_BLK_16:
		frame->blocks = 16;
		break;
	}

	frame->mode = (data[1] >> 2) & 0x03;
	switch (frame->mode) {
	case MONO:
		frame->channels = 1;
		break;
	case DUAL_CHANNEL:	/* fall-through */
	case STEREO:
	case JOINT_STEREO:
		frame->channels = 2;
		break;
	}

	frame->allocation = (data[1] >> 1) & 0x01;

	frame->subband_mode = (data[1] & 0x01);
	frame->subbands = frame->subband_mode ? 8 : 4;

	frame->bitpool = data[2];

	if ((frame->mode == MONO || frame->mode == DUAL_CHANNEL) &&
			frame->bitpool > 16 * frame->subbands)
		return -4;

	if ((frame->mode == STEREO || frame->mode == JOINT_STEREO) &&
			frame->bitpool > 32 * frame->subbands)
		return -4;

	/* data[3] is crc, we're checking it later */

	consumed = 32;

	crc_header[0] = data[1];
	crc_header[1] = data[2];
	crc_pos = 16;

	if (frame->mode == JOINT_STEREO) {
		if (len * 8 < consumed + frame->subbands)
			return -1;

		frame->joint = 0x00;
		for (sb = 0; sb < frame->subbands - 1; sb++)
			frame->joint |= ((data[4] >> (7 - sb)) & 0x01) << sb;
		if (frame->subbands == 4)
			crc_header[crc_pos / 8] = data[4] & 0xf0;
		else
			crc_header[crc_pos / 8] = data[4];

		consumed += frame->subbands;
		crc_pos += frame->subbands;
	}

	if (len * 8 < consumed + (4 * frame->subbands * frame->channels))
		return -1;

	for (ch = 0; ch < frame->channels; ch++) {
		for (sb = 0; sb < frame->subbands; sb++) {
			/* FIXME assert(consumed % 4 == 0); */
			frame->scale_factor[ch][sb] =
				(data[consumed >> 3] >> (4 - (consumed & 0x7))) & 0x0F;
			crc_header[crc_pos >> 3] |=
				frame->scale_factor[ch][sb] << (4 - (crc_pos & 0x7));

			consumed += 4;
			crc_pos += 4;
		}
	}

	if (data[3] != sbc_crc8(crc_header, crc_pos))
		return -3;