vl_rbsp.h revision 848b8605 
1/**************************************************************************
2 *
3 * Copyright 2013 Advanced Micro Devices, Inc.
4 * All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the
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11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
13 *
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
16 * of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
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23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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27
28/*
29 * Authors:
30 *      Christian König <christian.koenig@amd.com>
31 *
32 */
33
34/*
35 * Functions for reading the raw byte sequence payload of H.264
36 */
37
38#ifndef vl_rbsp_h
39#define vl_rbsp_h
40
41#include "vl/vl_vlc.h"
42
43struct vl_rbsp {
44   struct vl_vlc nal;
45   unsigned escaped;
46};
47
48/**
49 * Initialize the RBSP object
50 */
51static INLINE void vl_rbsp_init(struct vl_rbsp *rbsp, struct vl_vlc *nal, unsigned num_bits)
52{
53   unsigned bits_left = vl_vlc_bits_left(nal);
54
55   /* copy the position */
56   rbsp->nal = *nal;
57
58   rbsp->escaped = 0;
59
60   /* search for the end of the NAL unit */
61   while (vl_vlc_search_byte(nal, num_bits, 0x00)) {
62      if (vl_vlc_peekbits(nal, 24) == 0x000001 ||
63          vl_vlc_peekbits(nal, 32) == 0x00000001) {
64         vl_vlc_limit(&rbsp->nal, bits_left - vl_vlc_bits_left(nal));
65         return;
66      }
67      vl_vlc_eatbits(nal, 8);
68   }
69}
70
71/**
72 * Make at least 16 more bits available
73 */
74static INLINE void vl_rbsp_fillbits(struct vl_rbsp *rbsp)
75{
76   unsigned valid = vl_vlc_valid_bits(&rbsp->nal);
77   unsigned i, bits;
78
79   /* abort if we still have enough bits */
80   if (valid >= 32)
81      return;
82
83   vl_vlc_fillbits(&rbsp->nal);
84
85   /* abort if we have less than 24 bits left in this nal */
86   if (vl_vlc_bits_left(&rbsp->nal) < 24)
87      return;
88
89   /* check that we have enough bits left from the last fillbits */
90   assert(valid >= rbsp->escaped);
91
92   /* handle the already escaped bits */
93   valid -= rbsp->escaped;
94
95   /* search for the emulation prevention three byte */
96   rbsp->escaped = 16;
97   bits = vl_vlc_valid_bits(&rbsp->nal);
98   for (i = valid + 24; i <= bits; i += 8) {
99      if ((vl_vlc_peekbits(&rbsp->nal, i) & 0xffffff) == 0x3) {
100         vl_vlc_removebits(&rbsp->nal, i - 8, 8);
101         rbsp->escaped = bits - i;
102         bits -= 8;
103         i += 8;
104      }
105   }
106}
107
108/**
109 * Return an unsigned integer from the first n bits
110 */
111static INLINE unsigned vl_rbsp_u(struct vl_rbsp *rbsp, unsigned n)
112{
113   if (n == 0)
114      return 0;
115
116   vl_rbsp_fillbits(rbsp);
117   return vl_vlc_get_uimsbf(&rbsp->nal, n);
118}
119
120/**
121 * Return an unsigned exponential Golomb encoded integer
122 */
123static INLINE unsigned vl_rbsp_ue(struct vl_rbsp *rbsp)
124{
125   unsigned bits = 0;
126
127   vl_rbsp_fillbits(rbsp);
128   while (!vl_vlc_get_uimsbf(&rbsp->nal, 1))
129      ++bits;
130
131   return (1 << bits) - 1 + vl_rbsp_u(rbsp, bits);
132}
133
134/**
135 * Return an signed exponential Golomb encoded integer
136 */
137static INLINE signed vl_rbsp_se(struct vl_rbsp *rbsp)
138{
139   signed codeNum = vl_rbsp_ue(rbsp);
140   if (codeNum & 1)
141      return (codeNum + 1) >> 1;
142   else
143      return -(codeNum >> 1);
144}
145
146/**
147 * Are more data available in the RBSP ?
148 */
149static INLINE bool vl_rbsp_more_data(struct vl_rbsp *rbsp)
150{
151   unsigned bits, value;
152
153   if (vl_vlc_bits_left(&rbsp->nal) > 8)
154      return TRUE;
155
156   bits = vl_vlc_valid_bits(&rbsp->nal);
157   value = vl_vlc_peekbits(&rbsp->nal, bits);
158   if (value == 0 || value == (1 << (bits - 1)))
159      return FALSE;
160
161   return TRUE;
162}
163
164#endif /* vl_rbsp_h */
165