2 * RTJpeg decoding functions
3 * Copyright (c) 2006 Reimar Doeffinger
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 #include "bitstream.h"
24 #define PUT_COEFF(c) \
26 block[i] = (c) * quant[i];
28 //! aligns the bitstream to the give power of two
30 n = (-get_bits_count(gb)) & (a - 1); \
31 if (n) {skip_bits(gb, n);}
34 * \brief read one block from stream
35 * \param gb contains stream data
36 * \param block where data is written to
37 * \param scan array containing the mapping stream address -> block position
38 * \param quant quantization factors
40 * Note: GetBitContext is used to make the code simpler, since all data is
41 * aligned this could be done faster in a different way, e.g. as it is done
42 * in MPlayer libmpcodecs/native/RTjpegN.c
44 static inline int get_block(GetBitContext
*gb
, DCTELEM
*block
, uint8_t *scan
,
48 uint8_t dc
= get_bits(gb
, 8);
54 // number of non-zero coefficients
55 coeff
= get_bits(gb
, 6);
56 // normally we would only need to clear the (63 - coeff) last values,
57 // but since we do not know where they are we just clear the whole block
58 memset(block
, 0, 64 * sizeof(DCTELEM
));
60 // 2 bits per coefficient
62 ac
= get_sbits(gb
, 2);
64 break; // continue with more bits
68 // 4 bits per coefficient
71 ac
= get_sbits(gb
, 4);
73 break; // continue with more bits
77 // 8 bits per coefficient
80 ac
= get_sbits(gb
, 8);
89 * \brief decode one rtjpeg YUV420 frame
90 * \param c context, must be initialized via rtjpeg_decode_init
91 * \param f AVFrame to place decoded frame into. If parts of the frame
92 * are not coded they are left unchanged, so consider initializing it
93 * \param buf buffer containing input data
94 * \param buf_size length of input data in bytes
95 * \return number of bytes consumed from the input buffer
97 int rtjpeg_decode_frame_yuv420(RTJpegContext
*c
, AVFrame
*f
,
98 uint8_t *buf
, int buf_size
) {
100 int w
= c
->w
/ 16, h
= c
->h
/ 16;
102 void *y1
= f
->data
[0], *y2
= f
->data
[0] + 8 * f
->linesize
[0];
103 void *u
= f
->data
[1], *v
= f
->data
[2];
104 init_get_bits(&gb
, buf
, buf_size
* 8);
105 for (y
= 0; y
< h
; y
++) {
106 for (x
= 0; x
< w
; x
++) {
107 if (get_block(&gb
, c
->block
, c
->scan
, c
->lquant
))
108 c
->dsp
->idct_put(y1
, f
->linesize
[0], c
->block
);
110 if (get_block(&gb
, c
->block
, c
->scan
, c
->lquant
))
111 c
->dsp
->idct_put(y1
, f
->linesize
[0], c
->block
);
113 if (get_block(&gb
, c
->block
, c
->scan
, c
->lquant
))
114 c
->dsp
->idct_put(y2
, f
->linesize
[0], c
->block
);
116 if (get_block(&gb
, c
->block
, c
->scan
, c
->lquant
))
117 c
->dsp
->idct_put(y2
, f
->linesize
[0], c
->block
);
119 if (get_block(&gb
, c
->block
, c
->scan
, c
->cquant
))
120 c
->dsp
->idct_put(u
, f
->linesize
[1], c
->block
);
122 if (get_block(&gb
, c
->block
, c
->scan
, c
->cquant
))
123 c
->dsp
->idct_put(v
, f
->linesize
[2], c
->block
);
126 y1
+= 2 * 8 * (f
->linesize
[0] - w
);
127 y2
+= 2 * 8 * (f
->linesize
[0] - w
);
128 u
+= 8 * (f
->linesize
[1] - w
);
129 v
+= 8 * (f
->linesize
[2] - w
);
131 return get_bits_count(&gb
) / 8;
135 * \brief initialize an RTJpegContext, may be called multiple times
136 * \param c context to initialize
137 * \param dsp specifies the idct to use for decoding
138 * \param width width of image, will be rounded down to the nearest multiple
140 * \param height height of image, will be rounded down to the nearest multiple
142 * \param lquant luma quantization table to use
143 * \param cquant chroma quantization table to use
145 void rtjpeg_decode_init(RTJpegContext
*c
, DSPContext
*dsp
,
146 int width
, int height
,
147 uint32_t *lquant
, uint32_t *cquant
) {
150 for (i
= 0; i
< 64; i
++) {
151 int z
= ff_zigzag_direct
[i
];
152 int p
= c
->dsp
->idct_permutation
[i
];
153 z
= ((z
<< 3) | (z
>> 3)) & 63; // rtjpeg uses a transposed variant
155 // permute the scan and quantization tables for the chosen idct
156 c
->scan
[i
] = c
->dsp
->idct_permutation
[z
];
157 c
->lquant
[p
] = lquant
[i
];
158 c
->cquant
[p
] = cquant
[i
];