FFmpeg: libavcodec/mjpegbdec.c Source File

FFmpeg
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 FFmpeg.
6  *
7  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * Apple MJPEG-B decoder.
25  */
26 
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 
40  static int mjpegb_decode_frame(AVCodecContext *avctx,
41  void *data, int *got_frame,
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  GetBitContext hgb; /* for the header */
49  uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
50  uint32_t field_size, sod_offs;
51  int ret;
52 
53  buf_ptr = buf;
54  buf_end = buf + buf_size;
55  s->got_picture = 0;
56 
57 read_header:
58  /* reset on every SOI */
59  s->restart_interval = 0;
60  s->restart_count = 0;
61  s->mjpb_skiptosod = 0;
62 
63  if (buf_end - buf_ptr >= 1 << 28)
64  return AVERROR_INVALIDDATA;
65 
66  init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);
67 
68  skip_bits(&hgb, 32); /* reserved zeros */
69 
70  if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g'))
71  {
72  av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
73  return AVERROR_INVALIDDATA;
74  }
75 
76  field_size = get_bits_long(&hgb, 32); /* field size */
77  av_log(avctx, AV_LOG_DEBUG, "field size: 0x%x\n", field_size);
78  skip_bits(&hgb, 32); /* padded field size */
79  second_field_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "second_field_offs is %d and size is %d\n");
80  av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%x\n", second_field_offs);
81 
82  dqt_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dqt is %d and size is %d\n");
83  av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%x\n", dqt_offs);
84  if (dqt_offs)
85  {
86  init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
87  s->start_code = DQT;
88  if (ff_mjpeg_decode_dqt(s) < 0 &&
89  (avctx->err_recognition & AV_EF_EXPLODE))
90  return AVERROR_INVALIDDATA;
91  }
92 
93  dht_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dht is %d and size is %d\n");
94  av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%x\n", dht_offs);
95  if (dht_offs)
96  {
97  init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
98  s->start_code = DHT;
99  ff_mjpeg_decode_dht(s);
100  }
101 
102  sof_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
103  av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%x\n", sof_offs);
104  if (sof_offs)
105  {
106  init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
107  s->start_code = SOF0;
108  if (ff_mjpeg_decode_sof(s) < 0)
109  return -1;
110  }
111 
112  sos_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sos is %d and size is %d\n");
113  av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%x\n", sos_offs);
114  sod_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
115  av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%x\n", sod_offs);
116  if (sos_offs)
117  {
118  init_get_bits(&s->gb, buf_ptr + sos_offs,
119  8 * FFMIN(field_size, buf_end - buf_ptr - sos_offs));
120  s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
121  s->start_code = SOS;
122  if (ff_mjpeg_decode_sos(s, NULL, NULL) < 0 &&
123  (avctx->err_recognition & AV_EF_EXPLODE))
124  return AVERROR_INVALIDDATA;
125  }
126 
127  if (s->interlaced) {
128  s->bottom_field ^= 1;
129  /* if not bottom field, do not output image yet */
130  if (s->bottom_field != s->interlace_polarity && second_field_offs)
131  {
132  buf_ptr = buf + second_field_offs;
133  goto read_header;
134  }
135  }
136 
137  //XXX FIXME factorize, this looks very similar to the EOI code
138 
139  if(!s->got_picture) {
140  av_log(avctx, AV_LOG_WARNING, "no picture\n");
141  return buf_size;
142  }
143 
144  if ((ret = av_frame_ref(data, s->picture_ptr)) < 0)
145  return ret;
146  *got_frame = 1;
147 
148  if (!s->lossless && avctx->debug & FF_DEBUG_QP) {
149  av_log(avctx, AV_LOG_DEBUG, "QP: %d\n",
150  FFMAX3(s->qscale[0], s->qscale[1], s->qscale[2]));
151  }
152 
153  return buf_size;
154 }
155 
156  AVCodec ff_mjpegb_decoder = {
157  .name = "mjpegb",
158  .long_name = NULL_IF_CONFIG_SMALL("Apple MJPEG-B"),
159  .type = AVMEDIA_TYPE_VIDEO,
160  .id = AV_CODEC_ID_MJPEGB,
161  .priv_data_size = sizeof(MJpegDecodeContext),
162  .init = ff_mjpeg_decode_init,
163  .close = ff_mjpeg_decode_end,
164  .decode = mjpegb_decode_frame,
165  .capabilities = CODEC_CAP_DR1,
166  .max_lowres = 3,
167 };
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