/project/jni/sdl_sound/decoders/mpglib/layer1.c
https://github.com/aichunyu/FFPlayer · C · 148 lines · 122 code · 17 blank · 9 comment · 36 complexity · 0594dcae487d38afcb9474db7ddbf887 MD5 · raw file
- /*
- * Mpeg Layer-1 audio decoder
- * --------------------------
- * copyright (c) 1995 by Michael Hipp, All rights reserved. See also 'README'
- * near unoptimzed ...
- *
- * may have a few bugs after last optimization ...
- *
- */
- #include "mpg123_sdlsound.h"
- void I_step_one(unsigned int balloc[], unsigned int scale_index[2][SBLIMIT],struct frame *fr)
- {
- unsigned int *ba=balloc;
- unsigned int *sca = (unsigned int *) scale_index;
- if(fr->stereo) {
- int i;
- int jsbound = fr->jsbound;
- for (i=0;i<jsbound;i++) {
- *ba++ = getbits(4);
- *ba++ = getbits(4);
- }
- for (i=jsbound;i<SBLIMIT;i++)
- *ba++ = getbits(4);
- ba = balloc;
- for (i=0;i<jsbound;i++) {
- if ((*ba++))
- *sca++ = getbits(6);
- if ((*ba++))
- *sca++ = getbits(6);
- }
- for (i=jsbound;i<SBLIMIT;i++)
- if ((*ba++)) {
- *sca++ = getbits(6);
- *sca++ = getbits(6);
- }
- }
- else {
- int i;
- for (i=0;i<SBLIMIT;i++)
- *ba++ = getbits(4);
- ba = balloc;
- for (i=0;i<SBLIMIT;i++)
- if ((*ba++))
- *sca++ = getbits(6);
- }
- }
- void I_step_two(real fraction[2][SBLIMIT],unsigned int balloc[2*SBLIMIT],
- unsigned int scale_index[2][SBLIMIT],struct frame *fr)
- {
- int i,n;
- int smpb[2*SBLIMIT]; /* values: 0-65535 */
- int *sample;
- register unsigned int *ba;
- register unsigned int *sca = (unsigned int *) scale_index;
- if(fr->stereo) {
- int jsbound = fr->jsbound;
- register real *f0 = fraction[0];
- register real *f1 = fraction[1];
- ba = balloc;
- for (sample=smpb,i=0;i<jsbound;i++) {
- if ((n = *ba++))
- *sample++ = getbits(n+1);
- if ((n = *ba++))
- *sample++ = getbits(n+1);
- }
- for (i=jsbound;i<SBLIMIT;i++)
- if ((n = *ba++))
- *sample++ = getbits(n+1);
- ba = balloc;
- for (sample=smpb,i=0;i<jsbound;i++) {
- if((n=*ba++))
- *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
- else
- *f0++ = 0.0;
- if((n=*ba++))
- *f1++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
- else
- *f1++ = 0.0;
- }
- for (i=jsbound;i<SBLIMIT;i++) {
- if ((n=*ba++)) {
- real samp = ( ((-1)<<n) + (*sample++) + 1);
- *f0++ = samp * muls[n+1][*sca++];
- *f1++ = samp * muls[n+1][*sca++];
- }
- else
- *f0++ = *f1++ = 0.0;
- }
- }
- else {
- register real *f0 = fraction[0];
- ba = balloc;
- for (sample=smpb,i=0;i<SBLIMIT;i++)
- if ((n = *ba++))
- *sample++ = getbits(n+1);
- ba = balloc;
- for (sample=smpb,i=0;i<SBLIMIT;i++) {
- if((n=*ba++))
- *f0++ = (real) ( ((-1)<<n) + (*sample++) + 1) * muls[n+1][*sca++];
- else
- *f0++ = 0.0;
- }
- }
- }
- int do_layer1(struct frame *fr,unsigned char *pcm_sample,
- int *pcm_point,struct mpstr *mp)
- {
- int clip=0;
- int i,stereo = fr->stereo;
- unsigned int balloc[2*SBLIMIT];
- unsigned int scale_index[2][SBLIMIT];
- real fraction[2][SBLIMIT];
- int single = fr->single;
- fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? (fr->mode_ext<<2)+4 : 32;
- if(stereo == 1 || single == 3)
- single = 0;
- I_step_one(balloc,scale_index,fr);
- for (i=0;i<SCALE_BLOCK;i++)
- {
- I_step_two(fraction,balloc,scale_index,fr);
- if(single >= 0) {
- clip += synth_1to1_mono( (real*)fraction[single],pcm_sample,pcm_point,mp);
- }
- else {
- int p1 = *pcm_point;
- clip += synth_1to1( (real*)fraction[0],0,pcm_sample,&p1,mp);
- clip += synth_1to1( (real*)fraction[1],1,pcm_sample,pcm_point,mp);
- }
- }
- return clip;
- }