1 /* 2 * Copyright (c) 2010 The WebM project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef VPX_DSP_BITWRITER_H_ 12 #define VPX_DSP_BITWRITER_H_ 13 14 #include "vpx_ports/mem.h" 15 16 #include "vpx_dsp/prob.h" 17 18 #ifdef __cplusplus 19 extern "C" { 20 #endif 21 22 typedef struct vpx_writer { 23 unsigned int lowvalue; 24 unsigned int range; 25 int count; 26 unsigned int pos; 27 uint8_t *buffer; 28 } vpx_writer; 29 30 void vpx_start_encode(vpx_writer *bc, uint8_t *buffer); 31 void vpx_stop_encode(vpx_writer *bc); 32 33 static INLINE void vpx_write(vpx_writer *br, int bit, int probability) { 34 unsigned int split; 35 int count = br->count; 36 unsigned int range = br->range; 37 unsigned int lowvalue = br->lowvalue; 38 register int shift; 39 40 split = 1 + (((range - 1) * probability) >> 8); 41 42 range = split; 43 44 if (bit) { 45 lowvalue += split; 46 range = br->range - split; 47 } 48 49 shift = vpx_norm[range]; 50 51 range <<= shift; 52 count += shift; 53 54 if (count >= 0) { 55 int offset = shift - count; 56 57 if ((lowvalue << (offset - 1)) & 0x80000000) { 58 int x = br->pos - 1; 59 60 while (x >= 0 && br->buffer[x] == 0xff) { 61 br->buffer[x] = 0; 62 x--; 63 } 64 65 br->buffer[x] += 1; 66 } 67 68 br->buffer[br->pos++] = (lowvalue >> (24 - offset)); 69 lowvalue <<= offset; 70 shift = count; 71 lowvalue &= 0xffffff; 72 count -= 8; 73 } 74 75 lowvalue <<= shift; 76 br->count = count; 77 br->lowvalue = lowvalue; 78 br->range = range; 79 } 80 81 static INLINE void vpx_write_bit(vpx_writer *w, int bit) { 82 vpx_write(w, bit, 128); // vpx_prob_half 83 } 84 85 static INLINE void vpx_write_literal(vpx_writer *w, int data, int bits) { 86 int bit; 87 88 for (bit = bits - 1; bit >= 0; bit--) vpx_write_bit(w, 1 & (data >> bit)); 89 } 90 91 #define vpx_write_prob(w, v) vpx_write_literal((w), (v), 8) 92 93 #ifdef __cplusplus 94 } // extern "C" 95 #endif 96 97 #endif // VPX_DSP_BITWRITER_H_ 98
