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mtv.c
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1 /*
2  * mtv demuxer
3  * Copyright (c) 2006 Reynaldo H. Verdejo Pinochet
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  * MTV demuxer.
25  */
26 
27 #include "libavutil/bswap.h"
28 #include "libavutil/intreadwrite.h"
29 #include "avformat.h"
30 #include "internal.h"
31 
32 #define MTV_ASUBCHUNK_DATA_SIZE 500
33 #define MTV_HEADER_SIZE 512
34 #define MTV_AUDIO_PADDING_SIZE 12
35 #define MTV_IMAGE_DEFAULT_BPP 16
36 #define MTV_AUDIO_SAMPLING_RATE 44100
37 
38 typedef struct MTVDemuxContext {
39 
40  unsigned int file_size; ///< filesize, not always right
41  unsigned int segments; ///< number of 512 byte segments
42  unsigned int audio_identifier; ///< 'MP3' on all files I have seen
43  unsigned int audio_br; ///< bitrate of audio channel (mp3)
44  unsigned int img_colorfmt; ///< frame colorfmt rgb 565/555
45  unsigned int img_bpp; ///< frame bits per pixel
46  unsigned int img_width;
47  unsigned int img_height;
48  unsigned int img_segment_size; ///< size of image segment
49  unsigned int video_fps;
50  unsigned int full_segment_size;
51 
53 
54 static int mtv_probe(AVProbeData *p)
55 {
56  /* we need at least 57 bytes from the header
57  * to try parsing all required fields
58  */
59  if (p->buf_size < 57)
60  return 0;
61 
62  /* Magic is 'AMV' */
63  if (*p->buf != 'A' || *(p->buf + 1) != 'M' || *(p->buf + 2) != 'V')
64  return 0;
65 
66  /* Audio magic is always MP3 */
67  if (p->buf[43] != 'M' || p->buf[44] != 'P' || p->buf[45] != '3')
68  return 0;
69 
70  /* Check for nonzero in bpp and (width|height) header fields */
71  if(!(p->buf[51] && AV_RL16(&p->buf[52]) | AV_RL16(&p->buf[54])))
72  return 0;
73 
74  /* If width or height are 0 then imagesize header field should not */
75  if(!AV_RL16(&p->buf[52]) || !AV_RL16(&p->buf[54]))
76  {
77  if(!!AV_RL16(&p->buf[56]))
79  else
80  return 0;
81  }
82 
83  /* Image bpp is not an absolutely required
84  * field as we latter claim it should be 16
85  * no matter what. All samples in the wild
86  * are RGB565/555.
87  */
88  if(p->buf[51] != MTV_IMAGE_DEFAULT_BPP)
89  return AVPROBE_SCORE_EXTENSION / 2;
90 
91  /* We had enough data to parse header values
92  * but we expect to be able to get 512 bytes
93  * of header to be sure.
94  */
95  if (p->buf_size < MTV_HEADER_SIZE)
97 
98  return AVPROBE_SCORE_MAX;
99 }
100 
102 {
103  MTVDemuxContext *mtv = s->priv_data;
104  AVIOContext *pb = s->pb;
105  AVStream *st;
106  unsigned int audio_subsegments;
107 
108  avio_skip(pb, 3);
109  mtv->file_size = avio_rl32(pb);
110  mtv->segments = avio_rl32(pb);
111  avio_skip(pb, 32);
112  mtv->audio_identifier = avio_rl24(pb);
113  mtv->audio_br = avio_rl16(pb);
114  mtv->img_colorfmt = avio_rl24(pb);
115  mtv->img_bpp = avio_r8(pb)>>3;
116  mtv->img_width = avio_rl16(pb);
117  mtv->img_height = avio_rl16(pb);
118  mtv->img_segment_size = avio_rl16(pb);
119 
120  /* Assume 16bpp even if claimed otherwise.
121  * We know its going to be RGBG565/555 anyway
122  */
123  if (mtv->img_bpp != MTV_IMAGE_DEFAULT_BPP) {
124  av_log (s, AV_LOG_WARNING, "Header claims %dbpp (!= 16). Ignoring\n",
125  mtv->img_bpp);
127  }
128 
129  /* Calculate width and height if missing from header */
130 
131  if(!mtv->img_width && mtv->img_height)
132  mtv->img_width=mtv->img_segment_size / (mtv->img_bpp)
133  / mtv->img_height;
134 
135  if(!mtv->img_height && mtv->img_width)
136  mtv->img_height=mtv->img_segment_size / (mtv->img_bpp)
137  / mtv->img_width;
138 
139  if(!mtv->img_height || !mtv->img_width || !mtv->img_segment_size){
140  av_log(s, AV_LOG_ERROR, "width or height or segment_size is invalid and I cannot calculate them from other information\n");
141  return AVERROR(EINVAL);
142  }
143 
144  avio_skip(pb, 4);
145  audio_subsegments = avio_rl16(pb);
146 
147  if (audio_subsegments == 0) {
148  avpriv_request_sample(s, "MTV files without audio");
149  return AVERROR_PATCHWELCOME;
150  }
151 
152  mtv->full_segment_size =
153  audio_subsegments * (MTV_AUDIO_PADDING_SIZE + MTV_ASUBCHUNK_DATA_SIZE) +
154  mtv->img_segment_size;
155  mtv->video_fps = (mtv->audio_br / 4) / audio_subsegments;
156 
157  // FIXME Add sanity check here
158 
159  // all systems go! init decoders
160 
161  // video - raw rgb565
162 
163  st = avformat_new_stream(s, NULL);
164  if(!st)
165  return AVERROR(ENOMEM);
166 
167  avpriv_set_pts_info(st, 64, 1, mtv->video_fps);
171  st->codec->width = mtv->img_width;
172  st->codec->height = mtv->img_height;
173  st->codec->sample_rate = mtv->video_fps;
174  st->codec->extradata = av_strdup("BottomUp");
175  st->codec->extradata_size = 9;
176 
177  // audio - mp3
178 
179  st = avformat_new_stream(s, NULL);
180  if(!st)
181  return AVERROR(ENOMEM);
182 
186  st->codec->bit_rate = mtv->audio_br;
188 
189  // Jump over header
190 
191  if(avio_seek(pb, MTV_HEADER_SIZE, SEEK_SET) != MTV_HEADER_SIZE)
192  return AVERROR(EIO);
193 
194  return 0;
195 
196 }
197 
199 {
200  MTVDemuxContext *mtv = s->priv_data;
201  AVIOContext *pb = s->pb;
202  int ret;
203 
204  if((avio_tell(pb) - s->data_offset + mtv->img_segment_size) % mtv->full_segment_size)
205  {
207 
208  ret = av_get_packet(pb, pkt, MTV_ASUBCHUNK_DATA_SIZE);
209  if(ret < 0)
210  return ret;
211 
212  pkt->pos -= MTV_AUDIO_PADDING_SIZE;
213  pkt->stream_index = 1;
214 
215  }else
216  {
217  ret = av_get_packet(pb, pkt, mtv->img_segment_size);
218  if(ret < 0)
219  return ret;
220 
221  pkt->stream_index = 0;
222  }
223 
224  return ret;
225 }
226 
228  .name = "mtv",
229  .long_name = NULL_IF_CONFIG_SMALL("MTV"),
230  .priv_data_size = sizeof(MTVDemuxContext),
234 };