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30 * Christian König <christian.koenig@amd.com>
35 * Functions for reading the raw byte sequence payload of H.264
41 #include "vl/vl_vlc.h"
49 * Initialize the RBSP object
51 static inline void vl_rbsp_init(struct vl_rbsp
*rbsp
, struct vl_vlc
*nal
, unsigned num_bits
)
53 unsigned bits_left
= vl_vlc_bits_left(nal
);
55 /* copy the position */
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
));
67 vl_vlc_eatbits(nal
, 8);
72 * Make at least 16 more bits available
74 static inline void vl_rbsp_fillbits(struct vl_rbsp
*rbsp
)
76 unsigned valid
= vl_vlc_valid_bits(&rbsp
->nal
);
79 /* abort if we still have enough bits */
83 vl_vlc_fillbits(&rbsp
->nal
);
85 /* abort if we have less than 24 bits left in this nal */
86 if (vl_vlc_bits_left(&rbsp
->nal
) < 24)
89 /* check that we have enough bits left from the last fillbits */
90 assert(valid
>= rbsp
->escaped
);
92 /* handle the already escaped bits */
93 valid
-= rbsp
->escaped
;
95 /* search for the emulation prevention three byte */
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
;
109 * Return an unsigned integer from the first n bits
111 static inline unsigned vl_rbsp_u(struct vl_rbsp
*rbsp
, unsigned n
)
116 vl_rbsp_fillbits(rbsp
);
117 return vl_vlc_get_uimsbf(&rbsp
->nal
, n
);
121 * Return an unsigned exponential Golomb encoded integer
123 static inline unsigned vl_rbsp_ue(struct vl_rbsp
*rbsp
)
127 vl_rbsp_fillbits(rbsp
);
128 while (!vl_vlc_get_uimsbf(&rbsp
->nal
, 1))
131 return (1 << bits
) - 1 + vl_rbsp_u(rbsp
, bits
);
135 * Return an signed exponential Golomb encoded integer
137 static inline signed vl_rbsp_se(struct vl_rbsp
*rbsp
)
139 signed codeNum
= vl_rbsp_ue(rbsp
);
141 return (codeNum
+ 1) >> 1;
143 return -(codeNum
>> 1);
147 * Are more data available in the RBSP ?
149 static inline bool vl_rbsp_more_data(struct vl_rbsp
*rbsp
)
151 unsigned bits
, value
;
153 if (vl_vlc_bits_left(&rbsp
->nal
) > 8)
156 bits
= vl_vlc_valid_bits(&rbsp
->nal
);
157 value
= vl_vlc_peekbits(&rbsp
->nal
, bits
);
158 if (value
== 0 || value
== (1 << (bits
- 1)))
164 #endif /* vl_rbsp_h */