FFmpeg: libavformat/mxg.c Source File

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libavformat

mxg.c

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1 /*

2 * MxPEG clip file demuxer

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 */

22 #include "libavutil/channel_layout.h"

23 #include "libavutil/internal.h"

24 #include "libavutil/intreadwrite.h"

25 #include "libavcodec/mjpeg.h"

26 #include "avformat.h"

27 #include "internal.h"

28 #include "avio.h"

30 #define DEFAULT_PACKET_SIZE 1024

31 #define OVERREAD_SIZE 3

33 typedef struct MXGContext {

34 uint8_t *buffer;

35 uint8_t *buffer_ptr;

36 uint8_t *soi_ptr;

37 unsigned int buffer_size;

38 int64_t dts;

39 unsigned int cache_size;

40 } MXGContext;

42 static int mxg_read_header(AVFormatContext *s)

43 {

44 AVStream *video_st, *audio_st;

45 MXGContext *mxg = s->priv_data;

47 /* video parameters will be extracted from the compressed bitstream */

48 video_st = avformat_new_stream(s, NULL);

49 if (!video_st)

50 return AVERROR(ENOMEM);

51 video_st->codec->codec_type = AVMEDIA_TYPE_VIDEO;

52 video_st->codec->codec_id = AV_CODEC_ID_MXPEG;

53 avpriv_set_pts_info(video_st, 64, 1, 1000000);

55 audio_st = avformat_new_stream(s, NULL);

56 if (!audio_st)

57 return AVERROR(ENOMEM);

58 audio_st->codec->codec_type = AVMEDIA_TYPE_AUDIO;

59 audio_st->codec->codec_id = AV_CODEC_ID_PCM_ALAW;

60 audio_st->codec->channels = 1;

61 audio_st->codec->channel_layout = AV_CH_LAYOUT_MONO;

62 audio_st->codec->sample_rate = 8000;

63 audio_st->codec->bits_per_coded_sample = 8;

64 audio_st->codec->block_align = 1;

65 avpriv_set_pts_info(audio_st, 64, 1, 1000000);

67 mxg->soi_ptr = mxg->buffer_ptr = mxg->buffer = 0;

68 mxg->buffer_size = 0;

69 mxg->dts = AV_NOPTS_VALUE;

70 mxg->cache_size = 0;

72 return 0;

73 }

75 static uint8_t* mxg_find_startmarker(uint8_t *p, uint8_t *end)

76 {

77 for (; p < end - 3; p += 4) {

78 uint32_t x = AV_RN32(p);

80 if (x & (~(x+0x01010101)) & 0x80808080) {

81 if (p[0] == 0xff) {

82 return p;

83 } else if (p[1] == 0xff) {

84 return p+1;

85 } else if (p[2] == 0xff) {

86 return p+2;

87 } else if (p[3] == 0xff) {

88 return p+3;

89 }

90 }

91 }

93 for (; p < end; ++p) {

94 if (*p == 0xff) return p;

95 }

97 return end;

98 }

100 static int mxg_update_cache(AVFormatContext *s, unsigned int cache_size)

101 {

102 MXGContext *mxg = s->priv_data;

103 unsigned int current_pos = mxg->buffer_ptr - mxg->buffer;

104 unsigned int soi_pos;

105 uint8_t *buffer;

106 int ret;

107

108 /* reallocate internal buffer */

109 if (current_pos > current_pos + cache_size)

110 return AVERROR(ENOMEM);

111 soi_pos = mxg->soi_ptr - mxg->buffer;

112 buffer = av_fast_realloc(mxg->buffer, &mxg->buffer_size,

113 current_pos + cache_size +

114 FF_INPUT_BUFFER_PADDING_SIZE);

115 if (!buffer)

116 return AVERROR(ENOMEM);

117 mxg->buffer = buffer;

118 mxg->buffer_ptr = mxg->buffer + current_pos;

119 if (mxg->soi_ptr) mxg->soi_ptr = mxg->buffer + soi_pos;

120

121 /* get data */

122 ret = avio_read(s->pb, mxg->buffer_ptr + mxg->cache_size,

123 cache_size - mxg->cache_size);

124 if (ret < 0)

125 return ret;

126

127 mxg->cache_size += ret;

128

129 return ret;

130 }

131

132 static int mxg_read_packet(AVFormatContext *s, AVPacket *pkt)

133 {

134 int ret;

135 unsigned int size;

136 uint8_t *startmarker_ptr, *end, *search_end, marker;

137 MXGContext *mxg = s->priv_data;

138

139 while (!avio_feof(s->pb) && !s->pb->error){

140 if (mxg->cache_size <= OVERREAD_SIZE) {

141 /* update internal buffer */

142 ret = mxg_update_cache(s, DEFAULT_PACKET_SIZE + OVERREAD_SIZE);

143 if (ret < 0)

144 return ret;

145 }

146 end = mxg->buffer_ptr + mxg->cache_size;

147

148 /* find start marker - 0xff */

149 if (mxg->cache_size > OVERREAD_SIZE) {

150 search_end = end - OVERREAD_SIZE;

151 startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);

152 } else {

153 search_end = end;

154 startmarker_ptr = mxg_find_startmarker(mxg->buffer_ptr, search_end);

155 if (startmarker_ptr >= search_end - 1 ||

156 *(startmarker_ptr + 1) != EOI) break;

157 }

158

159 if (startmarker_ptr != search_end) { /* start marker found */

160 marker = *(startmarker_ptr + 1);

161 mxg->buffer_ptr = startmarker_ptr + 2;

162 mxg->cache_size = end - mxg->buffer_ptr;

163

164 if (marker == SOI) {

165 mxg->soi_ptr = startmarker_ptr;

166 } else if (marker == EOI) {

167 if (!mxg->soi_ptr) {

168 av_log(s, AV_LOG_WARNING, "Found EOI before SOI, skipping\n");

169 continue;

170 }

171

172 pkt->pts = pkt->dts = mxg->dts;

173 pkt->stream_index = 0;

174 #if FF_API_DESTRUCT_PACKET

175 FF_DISABLE_DEPRECATION_WARNINGS

176 pkt->destruct = NULL;

177 FF_ENABLE_DEPRECATION_WARNINGS

178 #endif

179 pkt->buf = NULL;

180 pkt->size = mxg->buffer_ptr - mxg->soi_ptr;

181 pkt->data = mxg->soi_ptr;

182

183 if (mxg->soi_ptr - mxg->buffer > mxg->cache_size) {

184 if (mxg->cache_size > 0) {

185 memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);

186 }

187

188 mxg->buffer_ptr = mxg->buffer;

189 }

190 mxg->soi_ptr = 0;

191

192 return pkt->size;

193 } else if ( (SOF0 <= marker && marker <= SOF15) ||

194 (SOS <= marker && marker <= COM) ) {

195 /* all other markers that start marker segment also contain

196 length value (see specification for JPEG Annex B.1) */

197 size = AV_RB16(mxg->buffer_ptr);

198 if (size < 2)

199 return AVERROR(EINVAL);

200

201 if (mxg->cache_size < size) {

202 ret = mxg_update_cache(s, size);

203 if (ret < 0)

204 return ret;

205 startmarker_ptr = mxg->buffer_ptr - 2;

206 mxg->cache_size = 0;

207 } else {

208 mxg->cache_size -= size;

209 }

210

211 mxg->buffer_ptr += size;

212

213 if (marker == APP13 && size >= 16) { /* audio data */

214 /* time (GMT) of first sample in usec since 1970, little-endian */

215 pkt->pts = pkt->dts = AV_RL64(startmarker_ptr + 8);

216 pkt->stream_index = 1;

217 #if FF_API_DESTRUCT_PACKET

218 FF_DISABLE_DEPRECATION_WARNINGS

219 pkt->destruct = NULL;

220 FF_ENABLE_DEPRECATION_WARNINGS

221 #endif

222 pkt->buf = NULL;

223 pkt->size = size - 14;

224 pkt->data = startmarker_ptr + 16;

225

226 if (startmarker_ptr - mxg->buffer > mxg->cache_size) {

227 if (mxg->cache_size > 0) {

228 memcpy(mxg->buffer, mxg->buffer_ptr, mxg->cache_size);

229 }

230 mxg->buffer_ptr = mxg->buffer;

231 }

232

233 return pkt->size;

234 } else if (marker == COM && size >= 18 &&

235 !strncmp(startmarker_ptr + 4, "MXF", 3)) {

236 /* time (GMT) of video frame in usec since 1970, little-endian */

237 mxg->dts = AV_RL64(startmarker_ptr + 12);

238 }

239 }

240 } else {

241 /* start marker not found */

242 mxg->buffer_ptr = search_end;

243 mxg->cache_size = OVERREAD_SIZE;

244 }

245 }

246

247 return AVERROR_EOF;

248 }

249

250 static int mxg_close(struct AVFormatContext *s)

251 {

252 MXGContext *mxg = s->priv_data;

253 av_freep(&mxg->buffer);

254 return 0;

255 }

256

257 AVInputFormat ff_mxg_demuxer = {

258 .name = "mxg",

259 .long_name = NULL_IF_CONFIG_SMALL("MxPEG clip"),

260 .priv_data_size = sizeof(MXGContext),

261 .read_header = mxg_read_header,

262 .read_packet = mxg_read_packet,

263 .read_close = mxg_close,

264 .extensions = "mxg",

265 };

Generated on Sun Mar 8 2015 02:35:11 for FFmpeg by doxygen 1.8.2