mjpegbdec.c
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1 /*
2  * Apple MJPEG-B decoder
3  * Copyright (c) 2002 Alex Beregszaszi
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
27 #include "avcodec.h"
28 #include "mjpeg.h"
29 #include "mjpegdec.h"
30 
31 static uint32_t read_offs(AVCodecContext *avctx, GetBitContext *gb, uint32_t size, const char *err_msg){
32  uint32_t offs= get_bits_long(gb, 32);
33  if(offs >= size){
34  av_log(avctx, AV_LOG_WARNING, err_msg, offs, size);
35  return 0;
36  }
37  return offs;
38 }
39 
41  void *data, int *data_size,
42  AVPacket *avpkt)
43 {
44  const uint8_t *buf = avpkt->data;
45  int buf_size = avpkt->size;
46  MJpegDecodeContext *s = avctx->priv_data;
47  const uint8_t *buf_end, *buf_ptr;
48  AVFrame *picture = data;
49  GetBitContext hgb; /* for the header */
50  uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
51  uint32_t field_size, sod_offs;
52 
53  buf_ptr = buf;
54  buf_end = buf + buf_size;
55 
57  /* reset on every SOI */
58  s->restart_interval = 0;
59  s->restart_count = 0;
60  s->mjpb_skiptosod = 0;
61 
62  if (buf_end - buf_ptr >= 1 << 28)
63  return AVERROR_INVALIDDATA;
64 
65  init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
66 
67  skip_bits(&hgb, 32); /* reserved zeros */
68 
69  if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
70  {
71  av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
72  return AVERROR_INVALIDDATA;
73  }
74 
75  field_size = get_bits_long(&hgb, 32); /* field size */
76  av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
77  skip_bits(&hgb, 32); /* padded field size */
78  second_field_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "second_field_offs is %d and size is %d\n");
79  av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
80 
81  dqt_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dqt is %d and size is %d\n");
82  av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
83  if (dqt_offs)
84  {
85  init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
86  s->start_code = DQT;
87  if (ff_mjpeg_decode_dqt(s) < 0 &&
88  (avctx->err_recognition & AV_EF_EXPLODE))
89  return AVERROR_INVALIDDATA;
90  }
91 
92  dht_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dht is %d and size is %d\n");
93  av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
94  if (dht_offs)
95  {
96  init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
97  s->start_code = DHT;
99  }
100 
101  sof_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
102  av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
103  if (sof_offs)
104  {
105  init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
106  s->start_code = SOF0;
107  if (ff_mjpeg_decode_sof(s) < 0)
108  return -1;
109  }
110 
111  sos_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sos is %d and size is %d\n");
112  av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
113  sod_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
114  av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
115  if (sos_offs)
116  {
117  init_get_bits(&s->gb, buf_ptr + sos_offs,
118  8 * FFMIN(field_size, buf_end - buf_ptr - sos_offs));
119  s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
120  s->start_code = SOS;
121  if (ff_mjpeg_decode_sos(s, NULL, NULL) < 0 &&
122  (avctx->err_recognition & AV_EF_EXPLODE))
123  return AVERROR_INVALIDDATA;
124  }
125 
126  if (s->interlaced) {
127  s->bottom_field ^= 1;
128  /* if not bottom field, do not output image yet */
129  if (s->bottom_field != s->interlace_polarity && second_field_offs)
130  {
131  buf_ptr = buf + second_field_offs;
132  second_field_offs = 0;
133  goto read_header;
134  }
135  }
136 
137  //XXX FIXME factorize, this looks very similar to the EOI code
138 
139  *picture= *s->picture_ptr;
140  *data_size = sizeof(AVFrame);
141 
142  if(!s->lossless){
143  picture->quality= FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]);
144  picture->qstride= 0;
145  picture->qscale_table= s->qscale_table;
146  memset(picture->qscale_table, picture->quality, (s->width+15)/16);
147  if(avctx->debug & FF_DEBUG_QP)
148  av_log(avctx, AV_LOG_DEBUG, "QP: %d\n", picture->quality);
149  picture->quality*= FF_QP2LAMBDA;
150  }
151 
152  return buf_size;
153 }
154 
156  .name = "mjpegb",
157  .type = AVMEDIA_TYPE_VIDEO,
158  .id = CODEC_ID_MJPEGB,
159  .priv_data_size = sizeof(MJpegDecodeContext),
163  .capabilities = CODEC_CAP_DR1,
164  .max_lowres = 3,
165  .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
166 };