Source code
Revision control
Copy as Markdown
Other Tools
/*
* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef VPX_VPX_DSP_BITWRITER_H_
#define VPX_VPX_DSP_BITWRITER_H_
#include <stdio.h>
#include "vpx_ports/compiler_attributes.h"
#include "vpx_ports/mem.h"
#include "vpx_dsp/prob.h"
#if CONFIG_BITSTREAM_DEBUG
#include "vpx_util/vpx_debug_util.h"
#endif // CONFIG_BITSTREAM_DEBUG
#ifdef __cplusplus
extern "C" {
#endif
typedef struct vpx_writer {
unsigned int lowvalue;
unsigned int range;
int count;
// Whether there has been an error.
int error;
// We maintain the invariant that pos <= size, i.e., we never write beyond
// the end of the buffer. If pos would be incremented to be greater than
// size, leave pos unchanged and set error to 1.
unsigned int pos;
unsigned int size;
uint8_t *buffer;
} vpx_writer;
void vpx_start_encode(vpx_writer *br, uint8_t *source, size_t size);
// Returns 0 on success and returns -1 in case of error.
int vpx_stop_encode(vpx_writer *br);
static INLINE VPX_NO_UNSIGNED_SHIFT_CHECK void vpx_write(vpx_writer *br,
int bit,
int probability) {
unsigned int split;
int count = br->count;
unsigned int range = br->range;
unsigned int lowvalue = br->lowvalue;
int shift;
#if CONFIG_BITSTREAM_DEBUG
/*
int queue_r = 0;
int frame_idx_r = 0;
int queue_w = bitstream_queue_get_write();
int frame_idx_w = bitstream_queue_get_frame_write();
if (frame_idx_w == frame_idx_r && queue_w == queue_r) {
fprintf(stderr, "\n *** bitstream queue at frame_idx_w %d queue_w %d\n",
frame_idx_w, queue_w);
assert(0);
}
*/
bitstream_queue_push(bit, probability);
#endif
split = 1 + (((range - 1) * probability) >> 8);
range = split;
if (bit) {
lowvalue += split;
range = br->range - split;
}
shift = vpx_norm[range];
range <<= shift;
count += shift;
if (count >= 0) {
int offset = shift - count;
if (!br->error) {
if ((lowvalue << (offset - 1)) & 0x80000000) {
int x = (int)br->pos - 1;
while (x >= 0 && br->buffer[x] == 0xff) {
br->buffer[x] = 0;
x--;
}
// TODO(wtc): How to prove x >= 0?
br->buffer[x] += 1;
}
if (br->pos < br->size) {
br->buffer[br->pos++] = (lowvalue >> (24 - offset)) & 0xff;
} else {
br->error = 1;
}
}
lowvalue <<= offset;
shift = count;
lowvalue &= 0xffffff;
count -= 8;
}
lowvalue <<= shift;
br->count = count;
br->lowvalue = lowvalue;
br->range = range;
}
static INLINE void vpx_write_bit(vpx_writer *w, int bit) {
vpx_write(w, bit, 128); // vpx_prob_half
}
static INLINE void vpx_write_literal(vpx_writer *w, int data, int bits) {
int bit;
for (bit = bits - 1; bit >= 0; bit--) vpx_write_bit(w, 1 & (data >> bit));
}
#define vpx_write_prob(w, v) vpx_write_literal((w), (v), 8)
#ifdef __cplusplus
} // extern "C"
#endif
#endif // VPX_VPX_DSP_BITWRITER_H_