mxg.c
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1 /*
2  * MxPEG clip file demuxer
3  * Copyright (c) 2010 Anatoly Nenashev
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 
22 #include "libavutil/intreadwrite.h"
23 #include "libavcodec/mjpeg.h"
24 #include "avformat.h"
25 #include "internal.h"
26 #include "avio.h"
27 
28 #define DEFAULT_PACKET_SIZE 1024
29 #define OVERREAD_SIZE 3
30 
31 typedef struct MXGContext {
32  uint8_t *buffer;
33  uint8_t *buffer_ptr;
34  uint8_t *soi_ptr;
35  unsigned int buffer_size;
36  int64_t dts;
37  unsigned int cache_size;
38 } MXGContext;
39 
41 {
42  AVStream *video_st, *audio_st;
43  MXGContext *mxg = s->priv_data;
44 
45  /* video parameters will be extracted from the compressed bitstream */
46  video_st = avformat_new_stream(s, NULL);
47  if (!video_st)
48  return AVERROR(ENOMEM);
49  video_st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
50  video_st->codec->codec_id = CODEC_ID_MXPEG;
51  avpriv_set_pts_info(video_st, 64, 1, 1000000);
52 
53  audio_st = avformat_new_stream(s, NULL);
54  if (!audio_st)
55  return AVERROR(ENOMEM);
56  audio_st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
57  audio_st->codec->codec_id = CODEC_ID_PCM_ALAW;
58  audio_st->codec->channels = 1;
59  audio_st->codec->sample_rate = 8000;
60  audio_st->codec->bits_per_coded_sample = 8;
61  audio_st->codec->block_align = 1;
62  avpriv_set_pts_info(audio_st, 64, 1, 1000000);
63 
64  mxg->soi_ptr = mxg->buffer_ptr = mxg->buffer = 0;
65  mxg->buffer_size = 0;
66  mxg->dts = AV_NOPTS_VALUE;
67  mxg->cache_size = 0;
68 
69  return 0;
70 }
71 
72 static uint8_t* mxg_find_startmarker(uint8_t *p, uint8_t *end)
73 {
74  for (; p < end - 3; p += 4) {
75  uint32_t x = *(uint32_t*)p;
76 
77  if (x & (~(x+0x01010101)) & 0x80808080) {
78  if (p[0] == 0xff) {
79  return p;
80  } else if (p[1] == 0xff) {
81  return p+1;
82  } else if (p[2] == 0xff) {
83  return p+2;
84  } else if (p[3] == 0xff) {
85  return p+3;
86  }
87  }
88  }
89 
90  for (; p < end; ++p) {
91  if (*p == 0xff) return p;
92  }
93 
94  return end;
95 }
96 
97 static int mxg_update_cache(AVFormatContext *s, unsigned int cache_size)
98 {
99  MXGContext *mxg = s->priv_data;
100  unsigned int current_pos = mxg->buffer_ptr - mxg->buffer;
101  unsigned int soi_pos;
102  int ret;
103 
104  /* reallocate internal buffer */
105  if (current_pos > current_pos + cache_size)
106  return AVERROR(ENOMEM);
107  if (mxg->soi_ptr) soi_pos = mxg->soi_ptr - mxg->buffer;
108  mxg->buffer = av_fast_realloc(mxg->buffer, &mxg->buffer_size,
109  current_pos + cache_size +
111  if (!mxg->buffer)
112  return AVERROR(ENOMEM);
113  mxg->buffer_ptr = mxg->buffer + current_pos;
114  if (mxg->soi_ptr) mxg->soi_ptr = mxg->buffer + soi_pos;
115 
116  /* get data */
117  ret = avio_read(s->pb, mxg->buffer_ptr + mxg->cache_size,
118  cache_size - mxg->cache_size);
119  if (ret < 0)
120  return ret;
121 
122  mxg->cache_size += ret;
123 
124  return ret;
125 }
126 
128 {
129  int ret;
130  unsigned int size;
131  uint8_t *startmarker_ptr, *end, *search_end, marker;
132  MXGContext *mxg = s->priv_data;
133 
134  while (!s->pb->eof_reached && !s->pb->error){
135  if (mxg->cache_size <= OVERREAD_SIZE) {
136  /* update internal buffer */
138  if (ret < 0)
139  return ret;
140  }
141  end = mxg->buffer_ptr + mxg->cache_size;
142 
143  /* find start marker - 0xff */
144  if (mxg->cache_size > OVERREAD_SIZE) {
145  search_end = end - OVERREAD_SIZE;
146  startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
147  } else {
148  search_end = end;
149  startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);
150  if (startmarker_ptr >= search_end - 1 ||
151  *(startmarker_ptr + 1) != EOI) break;
152  }
153 
154  if (startmarker_ptr != search_end) { /* start marker found */
155  marker = *(startmarker_ptr + 1);
156  mxg->buffer_ptr = startmarker_ptr + 2;
157  mxg->cache_size = end - mxg->buffer_ptr;
158 
159  if (marker == SOI) {
160  mxg->soi_ptr = startmarker_ptr;
161  } else if (marker == EOI) {
162  if (!mxg->soi_ptr) {
163  av_log(s, AV_LOG_WARNING, "Found EOI before SOI, skipping\n");
164  continue;
165  }
166 
167  pkt->pts = pkt->dts = mxg->dts;
168  pkt->stream_index = 0;
169  pkt->destruct = NULL;
170  pkt->size = mxg->buffer_ptr - mxg->soi_ptr;
171  pkt->data = mxg->soi_ptr;
172 
173  if (mxg->soi_ptr - mxg->buffer > mxg->cache_size) {
174  if (mxg->cache_size > 0) {
175  memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
176  }
177 
178  mxg->buffer_ptr = mxg->buffer;
179  }
180  mxg->soi_ptr = 0;
181 
182  return pkt->size;
183  } else if ( (SOF0 <= marker && marker <= SOF15) ||
184  (SOS <= marker && marker <= COM) ) {
185  /* all other markers that start marker segment also contain
186  length value (see specification for JPEG Annex B.1) */
187  size = AV_RB16(mxg->buffer_ptr);
188  if (size < 2)
189  return AVERROR(EINVAL);
190 
191  if (mxg->cache_size < size) {
192  ret = mxg_update_cache(s, size);
193  if (ret < 0)
194  return ret;
195  startmarker_ptr = mxg->buffer_ptr - 2;
196  mxg->cache_size = 0;
197  } else {
198  mxg->cache_size -= size;
199  }
200 
201  mxg->buffer_ptr += size;
202 
203  if (marker == APP13 && size >= 16) { /* audio data */
204  /* time (GMT) of first sample in usec since 1970, little-endian */
205  pkt->pts = pkt->dts = AV_RL64(startmarker_ptr + 8);
206  pkt->stream_index = 1;
207  pkt->destruct = NULL;
208  pkt->size = size - 14;
209  pkt->data = startmarker_ptr + 16;
210 
211  if (startmarker_ptr - mxg->buffer > mxg->cache_size) {
212  if (mxg->cache_size > 0) {
213  memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);
214  }
215  mxg->buffer_ptr = mxg->buffer;
216  }
217 
218  return pkt->size;
219  } else if (marker == COM && size >= 18 &&
220  !strncmp(startmarker_ptr + 4, "MXF", 3)) {
221  /* time (GMT) of video frame in usec since 1970, little-endian */
222  mxg->dts = AV_RL64(startmarker_ptr + 12);
223  }
224  }
225  } else {
226  /* start marker not found */
227  mxg->buffer_ptr = search_end;
228  mxg->cache_size = OVERREAD_SIZE;
229  }
230  }
231 
232  return AVERROR_EOF;
233 }
234 
235 static int mxg_close(struct AVFormatContext *s)
236 {
237  MXGContext *mxg = s->priv_data;
238  av_freep(&mxg->buffer);
239  return 0;
240 }
241 
243  .name = "mxg",
244  .long_name = NULL_IF_CONFIG_SMALL("MxPEG clip file format"),
245  .priv_data_size = sizeof(MXGContext),
249  .extensions = "mxg"
250 };