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336 lines
11 KiB
C
336 lines
11 KiB
C
/********************************************************************
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* *
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* THIS FILE IS PART OF THE OggTheora SOFTWARE CODEC SOURCE CODE. *
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* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
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* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
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* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
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* *
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* THE Theora SOURCE CODE IS COPYRIGHT (C) 2002-2009 *
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* by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
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* *
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********************************************************************
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function:
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last mod: $Id: idct.c 16503 2009-08-22 18:14:02Z giles $
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********************************************************************/
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#include <string.h>
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#include "internal.h"
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#include "dct.h"
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/*Performs an inverse 8 point Type-II DCT transform.
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The output is scaled by a factor of 2 relative to the orthonormal version of
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the transform.
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_y: The buffer to store the result in.
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Data will be placed in every 8th entry (e.g., in a column of an 8x8
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block).
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_x: The input coefficients.
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The first 8 entries are used (e.g., from a row of an 8x8 block).*/
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static void idct8(ogg_int16_t *_y,const ogg_int16_t _x[8]){
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ogg_int32_t t[8];
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ogg_int32_t r;
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/*Stage 1:*/
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/*0-1 butterfly.*/
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t[0]=OC_C4S4*(ogg_int16_t)(_x[0]+_x[4])>>16;
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t[1]=OC_C4S4*(ogg_int16_t)(_x[0]-_x[4])>>16;
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/*2-3 rotation by 6pi/16.*/
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t[2]=(OC_C6S2*_x[2]>>16)-(OC_C2S6*_x[6]>>16);
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t[3]=(OC_C2S6*_x[2]>>16)+(OC_C6S2*_x[6]>>16);
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/*4-7 rotation by 7pi/16.*/
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t[4]=(OC_C7S1*_x[1]>>16)-(OC_C1S7*_x[7]>>16);
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/*5-6 rotation by 3pi/16.*/
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t[5]=(OC_C3S5*_x[5]>>16)-(OC_C5S3*_x[3]>>16);
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t[6]=(OC_C5S3*_x[5]>>16)+(OC_C3S5*_x[3]>>16);
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t[7]=(OC_C1S7*_x[1]>>16)+(OC_C7S1*_x[7]>>16);
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/*Stage 2:*/
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/*4-5 butterfly.*/
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r=t[4]+t[5];
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t[5]=OC_C4S4*(ogg_int16_t)(t[4]-t[5])>>16;
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t[4]=r;
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/*7-6 butterfly.*/
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r=t[7]+t[6];
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t[6]=OC_C4S4*(ogg_int16_t)(t[7]-t[6])>>16;
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t[7]=r;
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/*Stage 3:*/
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/*0-3 butterfly.*/
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r=t[0]+t[3];
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t[3]=t[0]-t[3];
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t[0]=r;
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/*1-2 butterfly.*/
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r=t[1]+t[2];
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t[2]=t[1]-t[2];
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t[1]=r;
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/*6-5 butterfly.*/
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r=t[6]+t[5];
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t[5]=t[6]-t[5];
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t[6]=r;
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/*Stage 4:*/
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/*0-7 butterfly.*/
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_y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
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/*1-6 butterfly.*/
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_y[1<<3]=(ogg_int16_t)(t[1]+t[6]);
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/*2-5 butterfly.*/
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_y[2<<3]=(ogg_int16_t)(t[2]+t[5]);
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/*3-4 butterfly.*/
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_y[3<<3]=(ogg_int16_t)(t[3]+t[4]);
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_y[4<<3]=(ogg_int16_t)(t[3]-t[4]);
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_y[5<<3]=(ogg_int16_t)(t[2]-t[5]);
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_y[6<<3]=(ogg_int16_t)(t[1]-t[6]);
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_y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
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}
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/*Performs an inverse 8 point Type-II DCT transform.
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The output is scaled by a factor of 2 relative to the orthonormal version of
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the transform.
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_y: The buffer to store the result in.
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Data will be placed in every 8th entry (e.g., in a column of an 8x8
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block).
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_x: The input coefficients.
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Only the first 4 entries are used.
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The other 4 are assumed to be 0.*/
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static void idct8_4(ogg_int16_t *_y,const ogg_int16_t _x[8]){
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ogg_int32_t t[8];
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ogg_int32_t r;
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/*Stage 1:*/
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t[0]=OC_C4S4*_x[0]>>16;
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t[2]=OC_C6S2*_x[2]>>16;
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t[3]=OC_C2S6*_x[2]>>16;
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t[4]=OC_C7S1*_x[1]>>16;
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t[5]=-(OC_C5S3*_x[3]>>16);
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t[6]=OC_C3S5*_x[3]>>16;
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t[7]=OC_C1S7*_x[1]>>16;
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/*Stage 2:*/
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r=t[4]+t[5];
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t[5]=OC_C4S4*(ogg_int16_t)(t[4]-t[5])>>16;
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t[4]=r;
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r=t[7]+t[6];
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t[6]=OC_C4S4*(ogg_int16_t)(t[7]-t[6])>>16;
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t[7]=r;
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/*Stage 3:*/
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t[1]=t[0]+t[2];
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t[2]=t[0]-t[2];
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r=t[0]+t[3];
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t[3]=t[0]-t[3];
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t[0]=r;
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r=t[6]+t[5];
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t[5]=t[6]-t[5];
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t[6]=r;
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/*Stage 4:*/
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_y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
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_y[1<<3]=(ogg_int16_t)(t[1]+t[6]);
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_y[2<<3]=(ogg_int16_t)(t[2]+t[5]);
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_y[3<<3]=(ogg_int16_t)(t[3]+t[4]);
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_y[4<<3]=(ogg_int16_t)(t[3]-t[4]);
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_y[5<<3]=(ogg_int16_t)(t[2]-t[5]);
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_y[6<<3]=(ogg_int16_t)(t[1]-t[6]);
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_y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
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}
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/*Performs an inverse 8 point Type-II DCT transform.
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The output is scaled by a factor of 2 relative to the orthonormal version of
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the transform.
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_y: The buffer to store the result in.
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Data will be placed in every 8th entry (e.g., in a column of an 8x8
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block).
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_x: The input coefficients.
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Only the first 3 entries are used.
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The other 5 are assumed to be 0.*/
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static void idct8_3(ogg_int16_t *_y,const ogg_int16_t _x[8]){
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ogg_int32_t t[8];
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ogg_int32_t r;
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/*Stage 1:*/
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t[0]=OC_C4S4*_x[0]>>16;
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t[2]=OC_C6S2*_x[2]>>16;
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t[3]=OC_C2S6*_x[2]>>16;
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t[4]=OC_C7S1*_x[1]>>16;
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t[7]=OC_C1S7*_x[1]>>16;
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/*Stage 2:*/
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t[5]=OC_C4S4*t[4]>>16;
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t[6]=OC_C4S4*t[7]>>16;
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/*Stage 3:*/
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t[1]=t[0]+t[2];
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t[2]=t[0]-t[2];
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r=t[0]+t[3];
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t[3]=t[0]-t[3];
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t[0]=r;
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r=t[6]+t[5];
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t[5]=t[6]-t[5];
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t[6]=r;
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/*Stage 4:*/
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_y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
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_y[1<<3]=(ogg_int16_t)(t[1]+t[6]);
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_y[2<<3]=(ogg_int16_t)(t[2]+t[5]);
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_y[3<<3]=(ogg_int16_t)(t[3]+t[4]);
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_y[4<<3]=(ogg_int16_t)(t[3]-t[4]);
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_y[5<<3]=(ogg_int16_t)(t[2]-t[5]);
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_y[6<<3]=(ogg_int16_t)(t[1]-t[6]);
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_y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
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}
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/*Performs an inverse 8 point Type-II DCT transform.
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The output is scaled by a factor of 2 relative to the orthonormal version of
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the transform.
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_y: The buffer to store the result in.
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Data will be placed in every 8th entry (e.g., in a column of an 8x8
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block).
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_x: The input coefficients.
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Only the first 2 entries are used.
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The other 6 are assumed to be 0.*/
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static void idct8_2(ogg_int16_t *_y,const ogg_int16_t _x[8]){
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ogg_int32_t t[8];
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ogg_int32_t r;
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/*Stage 1:*/
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t[0]=OC_C4S4*_x[0]>>16;
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t[4]=OC_C7S1*_x[1]>>16;
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t[7]=OC_C1S7*_x[1]>>16;
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/*Stage 2:*/
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t[5]=OC_C4S4*t[4]>>16;
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t[6]=OC_C4S4*t[7]>>16;
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/*Stage 3:*/
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r=t[6]+t[5];
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t[5]=t[6]-t[5];
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t[6]=r;
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/*Stage 4:*/
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_y[0<<3]=(ogg_int16_t)(t[0]+t[7]);
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_y[1<<3]=(ogg_int16_t)(t[0]+t[6]);
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_y[2<<3]=(ogg_int16_t)(t[0]+t[5]);
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_y[3<<3]=(ogg_int16_t)(t[0]+t[4]);
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_y[4<<3]=(ogg_int16_t)(t[0]-t[4]);
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_y[5<<3]=(ogg_int16_t)(t[0]-t[5]);
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_y[6<<3]=(ogg_int16_t)(t[0]-t[6]);
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_y[7<<3]=(ogg_int16_t)(t[0]-t[7]);
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}
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/*Performs an inverse 8 point Type-II DCT transform.
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The output is scaled by a factor of 2 relative to the orthonormal version of
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the transform.
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_y: The buffer to store the result in.
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Data will be placed in every 8th entry (e.g., in a column of an 8x8
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block).
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_x: The input coefficients.
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Only the first entry is used.
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The other 7 are assumed to be 0.*/
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static void idct8_1(ogg_int16_t *_y,const ogg_int16_t _x[1]){
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_y[0<<3]=_y[1<<3]=_y[2<<3]=_y[3<<3]=
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_y[4<<3]=_y[5<<3]=_y[6<<3]=_y[7<<3]=(ogg_int16_t)(OC_C4S4*_x[0]>>16);
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}
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/*Performs an inverse 8x8 Type-II DCT transform.
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The input is assumed to be scaled by a factor of 4 relative to orthonormal
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version of the transform.
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All coefficients but the first 3 in zig-zag scan order are assumed to be 0:
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x x 0 0 0 0 0 0
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x 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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_y: The buffer to store the result in.
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This may be the same as _x.
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_x: The input coefficients.*/
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static void oc_idct8x8_3(ogg_int16_t _y[64],const ogg_int16_t _x[64]){
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const ogg_int16_t *in;
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ogg_int16_t *end;
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ogg_int16_t *out;
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ogg_int16_t w[64];
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/*Transform rows of x into columns of w.*/
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idct8_2(w,_x);
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idct8_1(w+1,_x+8);
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/*Transform rows of w into columns of y.*/
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for(in=w,out=_y,end=out+8;out<end;in+=8,out++)idct8_2(out,in);
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/*Adjust for the scale factor.*/
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for(out=_y,end=out+64;out<end;out++)*out=(ogg_int16_t)(*out+8>>4);
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}
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/*Performs an inverse 8x8 Type-II DCT transform.
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The input is assumed to be scaled by a factor of 4 relative to orthonormal
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version of the transform.
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All coefficients but the first 10 in zig-zag scan order are assumed to be 0:
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x x x x 0 0 0 0
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x x x 0 0 0 0 0
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x x 0 0 0 0 0 0
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x 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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0 0 0 0 0 0 0 0
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_y: The buffer to store the result in.
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This may be the same as _x.
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_x: The input coefficients.*/
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static void oc_idct8x8_10(ogg_int16_t _y[64],const ogg_int16_t _x[64]){
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const ogg_int16_t *in;
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ogg_int16_t *end;
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ogg_int16_t *out;
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ogg_int16_t w[64];
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/*Transform rows of x into columns of w.*/
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idct8_4(w,_x);
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idct8_3(w+1,_x+8);
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idct8_2(w+2,_x+16);
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idct8_1(w+3,_x+24);
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/*Transform rows of w into columns of y.*/
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for(in=w,out=_y,end=out+8;out<end;in+=8,out++)idct8_4(out,in);
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/*Adjust for the scale factor.*/
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for(out=_y,end=out+64;out<end;out++)*out=(ogg_int16_t)(*out+8>>4);
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}
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/*Performs an inverse 8x8 Type-II DCT transform.
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The input is assumed to be scaled by a factor of 4 relative to orthonormal
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version of the transform.
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_y: The buffer to store the result in.
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This may be the same as _x.
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_x: The input coefficients.*/
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static void oc_idct8x8_slow(ogg_int16_t _y[64],const ogg_int16_t _x[64]){
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const ogg_int16_t *in;
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ogg_int16_t *end;
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ogg_int16_t *out;
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ogg_int16_t w[64];
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/*Transform rows of x into columns of w.*/
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for(in=_x,out=w,end=out+8;out<end;in+=8,out++)idct8(out,in);
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/*Transform rows of w into columns of y.*/
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for(in=w,out=_y,end=out+8;out<end;in+=8,out++)idct8(out,in);
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/*Adjust for the scale factor.*/
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for(out=_y,end=out+64;out<end;out++)*out=(ogg_int16_t)(*out+8>>4);
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}
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void oc_idct8x8(const oc_theora_state *_state,ogg_int16_t _y[64],
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int _last_zzi){
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(*_state->opt_vtable.idct8x8)(_y,_last_zzi);
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}
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/*Performs an inverse 8x8 Type-II DCT transform.
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The input is assumed to be scaled by a factor of 4 relative to orthonormal
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version of the transform.*/
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void oc_idct8x8_c(ogg_int16_t _y[64],int _last_zzi){
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/*_last_zzi is subtly different from an actual count of the number of
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coefficients we decoded for this block.
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It contains the value of zzi BEFORE the final token in the block was
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decoded.
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In most cases this is an EOB token (the continuation of an EOB run from a
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previous block counts), and so this is the same as the coefficient count.
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However, in the case that the last token was NOT an EOB token, but filled
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the block up with exactly 64 coefficients, _last_zzi will be less than 64.
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Provided the last token was not a pure zero run, the minimum value it can
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be is 46, and so that doesn't affect any of the cases in this routine.
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However, if the last token WAS a pure zero run of length 63, then _last_zzi
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will be 1 while the number of coefficients decoded is 64.
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Thus, we will trigger the following special case, where the real
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coefficient count would not.
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Note also that a zero run of length 64 will give _last_zzi a value of 0,
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but we still process the DC coefficient, which might have a non-zero value
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due to DC prediction.
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Although convoluted, this is arguably the correct behavior: it allows us to
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use a smaller transform when the block ends with a long zero run instead
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of a normal EOB token.
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It could be smarter... multiple separate zero runs at the end of a block
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will fool it, but an encoder that generates these really deserves what it
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gets.
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Needless to say we inherited this approach from VP3.*/
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/*Then perform the iDCT.*/
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if(_last_zzi<3)oc_idct8x8_3(_y,_y);
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else if(_last_zzi<10)oc_idct8x8_10(_y,_y);
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else oc_idct8x8_slow(_y,_y);
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}
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