misc2.c

mp3解码程序

							if (is_pos==is_max[sfb+6]) is_pos=IS_ILLEGAL;
 
						a[0]=fras_s(global_gain[0],subblock_gain[0],scalefac_scale[0],scalefac[0]);
					}

                                        for (i=0;i<window_len;i++) {
                                                stereo_s(l,a,t_reorder[id][sfreq][l],ms_flag,is_pos,header);
                                                l++;
                                        }
                                }
                                sfb++;
                                window_len=t_s[sfb]-t_s[sfb-1];
                        }
                        while (l<576) {
			        int reorder = t_reorder[id][sfreq][l++];
			  
				xr[0][0][reorder]=xr[1][0][reorder]=0;
			}
                } else {                                                                       
        /*
	 * requantize_ms - short blocks w/stereo processing ********************
	 */
                        int window,window_len;

			ms_flag=find_isbound(isbound,gr,info,header);	
			sfb=0; l=0;
			window_len=t_s[0]+1;

                        while (l<(MAX(non_zero[0],non_zero[1]))) {
                                for (window=0;window<3;window++) {
					subblock_gain[0]=info->subblock_gain[gr][0][window];
					subblock_gain[1]=info->subblock_gain[gr][1][window];
					scalefac[0]=scalefac_s[gr][0][sfb][window];
					scalefac[1]=scalefac_s[gr][1][sfb][window];

                                        if (t_s[sfb] < isbound[window]) {
                                                is_pos=IS_ILLEGAL;
						a[0]=fras_s(global_gain[0],subblock_gain[0],scalefac_scale[0],scalefac[0]);
						a[1]=fras_s(global_gain[1],subblock_gain[1],scalefac_scale[1],scalefac[1]);
                                        } else {
                                                is_pos=scalefac[1];
                                                if (id==1) /* MPEG1 */
                                                        if (is_pos==7) is_pos=IS_ILLEGAL;
                                                else /* MPEG2 */
                                                        if (is_pos==is_max[sfb+6]) is_pos=IS_ILLEGAL;

                                                a[0]=fras_s(global_gain[0],subblock_gain[0],scalefac_scale[0],scalefac[0]);
                                        }

                                        for (i=0;i<window_len;i++) {
						stereo_s(l,a,t_reorder[id][sfreq][l],ms_flag,is_pos,header);
						l++;
					}
                                }
                                /* this won't do anymore
				 * window_len=-t_s[sfb]+t_s[++sfb];
				 */
				window_len  = -t_s[sfb++];
				window_len +=  t_s[sfb];

                        }
                        while (l<576) {
			        int reorder = t_reorder[id][sfreq][l++];
			  
				xr[0][0][reorder]=xr[1][0][reorder]=0;
			}
                }
        else {
        /*
	 * long blocks w/stereo processing *************************************
	 */
                int *preflag=info->preflag[gr];

		ms_flag=find_isbound(isbound,gr,info,header);

		sfb=0; l=0;
		scalefac[0]=scalefac_l[gr][0][sfb];
		a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
		scalefac[1]=scalefac_l[gr][1][sfb];
		a[1]=fras_l(sfb,global_gain[1],scalefac_scale[1],scalefac[1],preflag[1]);

		/* no intensity stereo part
		*/
	if (ms_flag)
                while (l< isbound[0]) {
#if defined(PENTIUM_RDTSC)

unsigned int cnt4, cnt3, cnt2, cnt1;
static int min_cycles = 99999999;

        __asm__(".byte 0x0f,0x31" : "=a" (cnt1), "=d" (cnt4));
#endif

			{
				register float Mi = fras2(is[0][l],a[0]);
				register float Si = fras2(is[1][l],a[1]);
				register float tmp = i_sq2;
				xr[0][0][l]=(Mi+Si)*tmp;
				xr[1][0][l]=(Mi-Si)*tmp;
			}

#if defined(PENTIUM_RDTSC)
                        __asm__(".byte 0x0f,0x31" : "=a" (cnt2), "=d" (cnt4));

                        if (cnt2-cnt1 < min_cycles) {
                          min_cycles = cnt2-cnt1;
                          printf("%d cycles\n", min_cycles);
                        }

#endif
                        if (l==t_l[sfb]) {
#if defined(PENTIUM_RDTSC2)

unsigned int cnt4, cnt2, cnt1;
static int min_cycles = 99999999;

        __asm__(".byte 0x0f,0x31" : "=a" (cnt1), "=d" (cnt4));
#endif

                                sfb++;
				scalefac[0]=scalefac_l[gr][0][sfb];
				a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
				scalefac[1]=scalefac_l[gr][1][sfb];
				a[1]=fras_l(sfb,global_gain[1],scalefac_scale[1],scalefac[1],preflag[1]);
#if defined(PENTIUM_RDTSC2)
                        __asm__(".byte 0x0f,0x31" : "=a" (cnt2), "=d" (cnt4));

                        if (cnt2-cnt1 < min_cycles) {
                          min_cycles = cnt2-cnt1;
                          printf("%d cycles, sfb %d\n", min_cycles, sfb);
                        }

#endif
                        }
                        l++;
                }
	else
                while (l< isbound[0]) {
                        xr[0][0][l]=fras2(is[0][l],a[0]);
                        xr[1][0][l]=fras2(is[1][l],a[1]);
                        if (l==t_l[sfb]) {
                                sfb++;
                                scalefac[0]=scalefac_l[gr][0][sfb];
                                a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
                                scalefac[1]=scalefac_l[gr][1][sfb];
                                a[1]=fras_l(sfb,global_gain[1],scalefac_scale[1],scalefac[1],preflag[1]);
                        }
                        l++;
                }


		/* intensity stereo part
		*/
		while (l<(MAX(non_zero[0],non_zero[1]))) {
			int is_pos=scalefac[1];
	
			if (id==1) /* MPEG1 */
				if (is_pos==7) is_pos=IS_ILLEGAL;
			else /* MPEG2 */
				if (is_pos==is_max[sfb]) is_pos=IS_ILLEGAL;

			stereo_l(l,a,ms_flag,is_pos,header);

			if (l==t_l[sfb]) {
				sfb++;
				scalefac[0]=scalefac_l[gr][0][sfb];
				scalefac[1]=scalefac_l[gr][1][sfb];
				a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
			}
			l++;
		}

                while (l<576) {
			xr[0][0][l]=0;
			xr[1][0][l]=0;
			l++;
		}
        }
}

/*
 * requantize_downmix **********************************************************
 */
void requantize_downmix(int gr,struct SIDE_INFO *info,struct AUDIO_HEADER *header)
{
int l,sfb,ms_flag,is_pos,i,ch;
int *global_gain,subblock_gain[2],*scalefac_scale,scalefac[2],isbound[3];
int sfreq=header->sampling_frequency;
int id = header->ID;
float a[2];

	/* first set some variables
	*/
	global_gain=info->global_gain[gr];
	scalefac_scale=info->scalefac_scale[gr];

	if (header->mode_extension==2 || header->mode_extension==3) ms_flag=1;
	else ms_flag=0;

	/* ... and then we're off for requantization
	*/
	if (info->window_switching_flag[gr][0] && info->block_type[gr][0]==2)
		if (info->mixed_block_flag[gr][0]) {
			die("mixed block? hmmmm...., downmix for mixed blocks is not yet implemented\n");
		} else {
			int window,window_len;
			int isbound[3];
			int is_pos;
			int dummy=find_isbound(isbound,gr,info,header); /* ugly hack, part3 */

			sfb=0; l=0; window_len=t_s[0]+1;
			
			while (l<(MAX(non_zero[0],non_zero[1]))) {
				for (window=0;window<3;window++) {
					subblock_gain[0]=info->subblock_gain[gr][0][window];
					subblock_gain[1]=info->subblock_gain[gr][1][window];
					scalefac[0]=scalefac_s[gr][0][sfb][window];
					is_pos=scalefac[1]=scalefac_s[gr][1][sfb][window];

					if (t_s[sfb] < isbound[window]) {
						a[0]=fras_s(global_gain[0],subblock_gain[0],scalefac_scale[0],scalefac[0]);
						if (ms_flag) {
							for (i=0;i<window_len;i++) {
								register float Mi=fras2(is[0][l],a[0]);
								register float tmp = i_sq2;
								xr[0][0][t_reorder[id][sfreq][l]]=Mi*i_sq2;
								l++;
							}
						} else {
							a[1]=fras_s(global_gain[1],subblock_gain[1],scalefac_scale[1],scalefac[1]);
							for (i=0;i<window_len;i++) {
								register float tmp1=fras2(is[0][l],a[0]);
								register float tmp2=fras2(is[1][l],a[1]);
								xr[0][0][t_reorder[id][sfreq][l]]=(tmp1+tmp2)*0.5f;
								l++;
							}
						}
					} else {
						a[0]=fras_s(global_gain[0],subblock_gain[0],scalefac_scale[0],scalefac[0]);
						for (i=0;i<window_len;i++) {
							register float ftmp = fras2(is[0][l], a[0]);
							if (id==0 && is_pos<is_max[sfb])
								ftmp*=t_downmix[intensity_scale][(is_pos+1)>>1];
							xr[0][0][t_reorder[id][sfreq][l]] = ftmp;
							l++;
						}						
					}
				}
				window_len  = -t_s[sfb++];
				window_len +=  t_s[sfb];
			}
			while (l<576) {
				xr[0][0][l]=0;
				l++;
			}
		}
	else {
		int *preflag=info->preflag[gr];
		int isbound;

		if (header->mode_extension==1 || header->mode_extension==3) {
			int tmp=non_zero[1];
			while (is[1][tmp] == 0) tmp--;
			sfb=0; while (t_l[sfb] < tmp && sfb < 21) sfb++;
			isbound=t_l[sfb]+1;
			no_of_imdcts[0]=no_of_imdcts[1]=(non_zero[0]-1)/18+1;
		} else {
			isbound=(MAX(non_zero[0],non_zero[1]));
			no_of_imdcts[0]=no_of_imdcts[1]=(isbound-1)/18+1;
		}

                sfb=0; l=0;
                scalefac[0]=scalefac_l[gr][0][sfb];
                a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
                scalefac[1]=scalefac_l[gr][1][sfb];
                a[1]=fras_l(sfb,global_gain[1],scalefac_scale[1],scalefac[1],preflag[1]);		

		/* no intensity stereo part
		 */
		if (ms_flag)
			while (l < isbound) {
				register float Mi = fras2(is[0][l],a[0]);
				register float tmp = i_sq2;
				xr[0][0][l]=Mi*tmp;

				if (l==t_l[sfb]) {
					sfb++;
                                	scalefac[0]=scalefac_l[gr][0][sfb];
                                	a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
					scalefac[1]=scalefac_l[gr][1][sfb];
				}
				l++;
			}
		else 
			while (l < isbound) {
				register float tmp1=fras2(is[0][l],a[0]);
				register float tmp2=fras2(is[1][l],a[1]);
				xr[0][0][l]=(tmp1+tmp2)*0.5f;
	                        if (l==t_l[sfb]) {
        	                        sfb++;
                	                scalefac[0]=scalefac_l[gr][0][sfb];
                        	        a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
                                	scalefac[1]=scalefac_l[gr][1][sfb];
                                	a[1]=fras_l(sfb,global_gain[1],scalefac_scale[1],scalefac[1],preflag[1]);
                        	}
                        	l++;
			}
		/* intensity stereo part
		*/
		while (l<(MAX(non_zero[0],non_zero[1]))) {
			int is_pos=scalefac[1];
			register float ftmp=fras2(is[0][l], a[0]);

			if (id==0  && is_pos<is_max[sfb]) {
				ftmp*=t_downmix[intensity_scale][(is_pos+1)>>1];
			}

			xr[0][0][l] = ftmp;

			if (l==t_l[sfb]) {
				sfb++;
				scalefac[0]=scalefac_l[gr][0][sfb];
				a[0]=fras_l(sfb,global_gain[0],scalefac_scale[0],scalefac[0],preflag[0]);
				scalefac[1]=scalefac_l[gr][1][sfb];
			}
			l++;
		}

		/* _always_ zero out everything else
		*/
		while (l<576) {
			xr[0][0][l]=0;
			l++;
		}
	}
}

/* 
 * antialiasing butterflies ****************************************************
 * 
 */
void alias_reduction(int ch)
{
unsigned int sb;

        for (sb=1;sb<32;sb++) {
	        float *x = xr[ch][sb];
		register float a, b;

	        a = x[0];
		b = x[-1];
                x[-1] = b * Cs[0] - a * Ca[0];
                x[0]  = a * Cs[0] + b * Ca[0];

	        a = x[1];
		b = x[-2];
                x[-2] = b * Cs[1] - a * Ca[1];
                x[1]  = a * Cs[1] + b * Ca[1];

	        a = x[2];
		b = x[-3];
                x[-3] = b * Cs[2] - a * Ca[2];
                x[2]  = a * Cs[2] + b * Ca[2];

	        a = x[3];
		b = x[-4];
                x[-4] = b * Cs[3] - a * Ca[3];
                x[3]  = a * Cs[3] + b * Ca[3];

	        a = x[4];
		b = x[-5];
                x[-5] = b * Cs[4] - a * Ca[4];
                x[4]  = a * Cs[4] + b * Ca[4];

	        a = x[5];
		b = x[-6];
                x[-6] = b * Cs[5] - a * Ca[5];
                x[5]  = a * Cs[5] + b * Ca[5];

	        a = x[6];
		b = x[-7];
                x[-7] = b * Cs[6] - a * Ca[6];
                x[6]  = a * Cs[6] + b * Ca[6];

	        a = x[7];
		b = x[-8];
                x[-8] = b * Cs[7] - a * Ca[7];
                x[7]  = a * Cs[7] + b * Ca[7];
	}
}

/* calculating t_43 instead of having that big table in misc2.h
 */

void calculate_t43(void)
{
int i;
	for (i=0;i<8192;i++)
		t_43[i]=(float)pow((float)i,1.33333333333f);
}