layer2.c

xmms-1.2.10.tar.gz学习使用的就下吧

/* 
 * Mpeg Layer-2 audio decoder 
 * --------------------------
 * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
 *
 */

#include "mpg123.h"
#include "l2tables.h"
#include "getbits.h"

static int grp_3tab[32 * 3] =
{0,};				/* used: 27 */
static int grp_5tab[128 * 3] =
{0,};				/* used: 125 */
static int grp_9tab[1024 * 3] =
{0,};				/* used: 729 */

real mpg123_muls[27][64];	/* also used by layer 1 */

/* Used by the getbits macros */
static unsigned long rval;

void mpg123_init_layer2(gboolean mmx)
{
	static double mulmul[27] = {
		0.0, -2.0 / 3.0, 2.0 / 3.0, 2.0 / 7.0, 2.0 / 15.0,
		2.0 / 31.0, 2.0 / 63.0, 2.0 / 127.0, 2.0 / 255.0,
		2.0 / 511.0, 2.0 / 1023.0, 2.0 / 2047.0, 2.0 / 4095.0,
		2.0 / 8191.0, 2.0 / 16383.0, 2.0 / 32767.0, 2.0 / 65535.0,
		-4.0 / 5.0, -2.0 / 5.0, 2.0 / 5.0, 4.0 / 5.0, -8.0 / 9.0,
		-4.0 / 9.0, -2.0 / 9.0, 2.0 / 9.0, 4.0 / 9.0, 8.0 / 9.0	};
	static int base[3][9] = {
		{1, 0, 2,},
		{17, 18, 0, 19, 20,},
		{21, 1, 22, 23, 0, 24, 25, 2, 26}};
	int i, j, k, l, len;
	real *table;
	static int tablen[3] = {3, 5, 9};
	static int *itable, *tables[3] =
	{grp_3tab, grp_5tab, grp_9tab};

	for (i = 0; i < 3; i++)
	{
		itable = tables[i];
		len = tablen[i];
		for (j = 0; j < len; j++)
			for (k = 0; k < len; k++)
				for (l = 0; l < len; l++)
				{
					*itable++ = base[i][l];
					*itable++ = base[i][k];
					*itable++ = base[i][j];
				}
	}

	for (k = 0; k < 27; k++)
	{
		double m = mulmul[k];
		table = mpg123_muls[k];
#ifdef USE_SIMD
		if (mmx)
			for(j = 3, i = 0; i < 63; i++, j--)
				*table++ = 16384 * m * pow(2.0,(double) j / 3.0);
		else
#endif
		for (j = 3, i = 0; i < 63; i++, j--)
			*table++ = m * pow(2.0, (double) j / 3.0);
		*table++ = 0.0;
	}
}

void II_step_one(unsigned int *bit_alloc, int *scale, struct frame *fr)
{
	int stereo = fr->stereo - 1;
	int sblimit = fr->II_sblimit;
	int jsbound = fr->jsbound;
	int sblimit2 = fr->II_sblimit << stereo;
	struct al_table *alloc1 = fr->alloc;
	int i;
	static unsigned int scfsi_buf[64];
	unsigned int *scfsi, *bita;
	int sc, step;

	bita = bit_alloc;
	if (stereo)
	{
		for (i = jsbound; i > 0; i--, alloc1 += (1 << step))
		{
			*bita++ = (char) mpg123_getbits(step = alloc1->bits);
			*bita++ = (char) mpg123_getbits(step);
		}
		for (i = sblimit - jsbound; i > 0; i--, alloc1 += (1 << step))
		{
			bita[0] = (char) mpg123_getbits(step = alloc1->bits);
			bita[1] = bita[0];
			bita += 2;
		}
		bita = bit_alloc;
		scfsi = scfsi_buf;
		for (i = sblimit2; i; i--)
			if (*bita++)
				*scfsi++ = (char) mpg123_getbits_fast(2);
	}
	else
		/* mono */
	{
		for (i = sblimit; i; i--, alloc1 += (1 << step))
			*bita++ = (char) mpg123_getbits(step = alloc1->bits);
		bita = bit_alloc;
		scfsi = scfsi_buf;
		for (i = sblimit; i; i--)
			if (*bita++)
				*scfsi++ = (char) mpg123_getbits_fast(2);
	}

	bita = bit_alloc;
	scfsi = scfsi_buf;
	for (i = sblimit2; i; i--)
		if (*bita++)
			switch (*scfsi++)
			{
				case 0:
					*scale++ = mpg123_getbits_fast(6);
					*scale++ = mpg123_getbits_fast(6);
					*scale++ = mpg123_getbits_fast(6);
					break;
				case 1:
					*scale++ = sc = mpg123_getbits_fast(6);
					*scale++ = sc;
					*scale++ = mpg123_getbits_fast(6);
					break;
				case 2:
					*scale++ = sc = mpg123_getbits_fast(6);
					*scale++ = sc;
					*scale++ = sc;
					break;
				default:	/* case 3 */
					*scale++ = mpg123_getbits_fast(6);
					*scale++ = sc = mpg123_getbits_fast(6);
					*scale++ = sc;
					break;
			}

}

void II_step_two(unsigned int *bit_alloc, real fraction[2][4][SBLIMIT], int *scale, struct frame *fr, int x1)
{
	int i, j, k, ba;
	int stereo = fr->stereo;
	int sblimit = fr->II_sblimit;
	int jsbound = fr->jsbound;
	struct al_table *alloc2, *alloc1 = fr->alloc;
	unsigned int *bita = bit_alloc;
	int d1, step;

	for (i = 0; i < jsbound; i++, alloc1 += (1 << step))
	{
		step = alloc1->bits;
		for (j = 0; j < stereo; j++)
		{
			if ((ba = *bita++))
			{
				k = (alloc2 = alloc1 + ba)->bits;
				if ((d1 = alloc2->d) < 0)
				{
					real cm = mpg123_muls[k][scale[x1]];

					fraction[j][0][i] = ((real) ((int) mpg123_getbits(k) + d1)) * cm;
					fraction[j][1][i] = ((real) ((int) mpg123_getbits(k) + d1)) * cm;
					fraction[j][2][i] = ((real) ((int) mpg123_getbits(k) + d1)) * cm;
				}
				else
				{
					static int *table[] =
					{0, 0, 0, grp_3tab, 0, grp_5tab, 0, 0, 0, grp_9tab};
					unsigned int idx, *tab, m = scale[x1];

					idx = (unsigned int) mpg123_getbits(k);
					tab = (unsigned int *) (table[d1] + idx + idx + idx);
					fraction[j][0][i] = mpg123_muls[*tab++][m];
					fraction[j][1][i] = mpg123_muls[*tab++][m];
					fraction[j][2][i] = mpg123_muls[*tab][m];
				}
				scale += 3;
			}
			else
				fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = 0.0;
		}
	}

	for (i = jsbound; i < sblimit; i++, alloc1 += (1 << step))
	{
		step = alloc1->bits;
		bita++;		/* channel 1 and channel 2 bitalloc are the same */
		if ((ba = *bita++))
		{
			k = (alloc2 = alloc1 + ba)->bits;
			if ((d1 = alloc2->d) < 0)
			{
				real cm;

				cm = mpg123_muls[k][scale[x1 + 3]];
				fraction[1][0][i] = (fraction[0][0][i] = (real) ((int) mpg123_getbits(k) + d1)) * cm;
				fraction[1][1][i] = (fraction[0][1][i] = (real) ((int) mpg123_getbits(k) + d1)) * cm;
				fraction[1][2][i] = (fraction[0][2][i] = (real) ((int) mpg123_getbits(k) + d1)) * cm;
				cm = mpg123_muls[k][scale[x1]];
				fraction[0][0][i] *= cm;
				fraction[0][1][i] *= cm;
				fraction[0][2][i] *= cm;
			}
			else
			{
				static int *table[] =
				{0, 0, 0, grp_3tab, 0, grp_5tab, 0, 0, 0, grp_9tab};
				unsigned int idx, *tab, m1, m2;

				m1 = scale[x1];
				m2 = scale[x1 + 3];
				idx = (unsigned int) mpg123_getbits(k);
				tab = (unsigned int *) (table[d1] + idx + idx + idx);
				fraction[0][0][i] = mpg123_muls[*tab][m1];
				fraction[1][0][i] = mpg123_muls[*tab++][m2];
				fraction[0][1][i] = mpg123_muls[*tab][m1];
				fraction[1][1][i] = mpg123_muls[*tab++][m2];
				fraction[0][2][i] = mpg123_muls[*tab][m1];
				fraction[1][2][i] = mpg123_muls[*tab][m2];
			}
			scale += 6;
		}
		else
		{
			fraction[0][0][i] = fraction[0][1][i] = fraction[0][2][i] =
				fraction[1][0][i] = fraction[1][1][i] = fraction[1][2][i] = 0.0;
		}
/* 
   should we use individual scalefac for channel 2 or
   is the current way the right one , where we just copy channel 1 to
   channel 2 ?? 
   The current 'strange' thing is, that we throw away the scalefac
   values for the second channel ...!!
   -> changed .. now we use the scalefac values of channel one !! 
 */
	}

	if (sblimit > (fr->down_sample_sblimit))
		sblimit = fr->down_sample_sblimit;

	for (i = sblimit; i < SBLIMIT; i++)
		for (j = 0; j < stereo; j++)
			fraction[j][0][i] = fraction[j][1][i] = fraction[j][2][i] = 0.0;

}

static void II_select_table(struct frame *fr)
{
	static int translate[3][2][16] = {
		{{0, 2, 2, 2, 2, 2, 2, 0, 0, 0, 1, 1, 1, 1, 1, 0},
		 {0, 2, 2, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0}},
		{{0, 2, 2, 2, 2, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0},
		 {0, 2, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
		{{0, 3, 3, 3, 3, 3, 3, 0, 0, 0, 1, 1, 1, 1, 1, 0},
		 {0, 3, 3, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0}}
	};

	int table, sblim;
	static struct al_table *tables[5] =
		{alloc_0, alloc_1, alloc_2, alloc_3, alloc_4};
	static int sblims[5] = { 27, 30, 8, 12, 30 };

	if (fr->lsf)
		table = 4;
	else
		table =	translate[fr->sampling_frequency][2 - fr->stereo][fr->bitrate_index];
	sblim = sblims[table];

	fr->alloc = tables[table];
	fr->II_sblimit = sblim;
}


int mpg123_do_layer2(struct frame *fr)
{
	int i, j;
	int stereo = fr->stereo;
	real fraction[2][4][SBLIMIT];	/* pick_table clears unused subbands */
	unsigned int bit_alloc[64];
	int scale[192];
	int single = fr->single;

	II_select_table(fr);
	fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ?
		(fr->mode_ext << 2) + 4 : fr->II_sblimit;
	if (fr->jsbound > fr->II_sblimit)
		fr->jsbound = fr->II_sblimit;

	if (stereo == 1 || single == 3)
		single = 0;

	II_step_one(bit_alloc, scale, fr);

	for (i = 0; i < SCALE_BLOCK; i++)
	{
		II_step_two(bit_alloc, fraction, scale, fr, i >> 2);
		for (j = 0; j < 3; j++)
		{
			if (single >= 0)
			{
				(fr->synth_mono) (fraction[single][j], mpg123_pcm_sample, &mpg123_pcm_point);
			}
			else
			{
				int p1 = mpg123_pcm_point;

				(fr->synth) (fraction[0][j], 0, mpg123_pcm_sample, &p1);
				(fr->synth) (fraction[1][j], 1, mpg123_pcm_sample, &mpg123_pcm_point);
			}

			/*    if(mpg123_pcm_point >= audiobufsize)
			   audio_flush(outmode,ai); */
		}
	}
	if (mpg123_info->output_audio)
	{

		mpg123_ip.add_vis_pcm(mpg123_ip.output->written_time(), mpg123_cfg.resolution == 16 ? FMT_S16_NE : FMT_U8,
				      mpg123_cfg.channels == 2 ? fr->stereo : 1, mpg123_pcm_point, mpg123_pcm_sample);

		while (mpg123_ip.output->buffer_free() < mpg123_pcm_point && mpg123_info->going && mpg123_info->jump_to_time == -1)
			xmms_usleep(10000);
		if (mpg123_info->going && mpg123_info->jump_to_time == -1)
			mpg123_ip.output->write_audio(mpg123_pcm_sample, mpg123_pcm_point);
		

	}
	mpg123_pcm_point = 0;

	return 1;
}