FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
mtv.c
Go to the documentation of this file.
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 AUDIO_SAMPLING_RATE 44100
36 
37 typedef struct MTVDemuxContext {
38 
39  unsigned int file_size; ///< filesize, not always right
40  unsigned int segments; ///< number of 512 byte segments
41  unsigned int audio_identifier; ///< 'MP3' on all files I have seen
42  unsigned int audio_br; ///< bitrate of audio channel (mp3)
43  unsigned int img_colorfmt; ///< frame colorfmt rgb 565/555
44  unsigned int img_bpp; ///< frame bits per pixel
45  unsigned int img_width;
46  unsigned int img_height;
47  unsigned int img_segment_size; ///< size of image segment
48  unsigned int video_fps;
49  unsigned int full_segment_size;
50 
52 
53 static int mtv_probe(AVProbeData *p)
54 {
55  /* Magic is 'AMV' */
56  if (*p->buf != 'A' || *(p->buf + 1) != 'M' || *(p->buf + 2) != 'V')
57  return 0;
58 
59  /* Check for nonzero in bpp and (width|height) header fields */
60  if(p->buf_size < 57 || !(p->buf[51] && AV_RL16(&p->buf[52]) | AV_RL16(&p->buf[54])))
61  return 0;
62 
63  /* If width or height are 0 then imagesize header field should not */
64  if(!AV_RL16(&p->buf[52]) || !AV_RL16(&p->buf[54]))
65  {
66  if(!!AV_RL16(&p->buf[56]))
68  else
69  return 0;
70  }
71 
72  if(p->buf[51] != 16)
73  return AVPROBE_SCORE_EXTENSION / 2; // But we are going to assume 16bpp anyway ..
74 
75  return AVPROBE_SCORE_MAX;
76 }
77 
79 {
80  MTVDemuxContext *mtv = s->priv_data;
81  AVIOContext *pb = s->pb;
82  AVStream *st;
83  unsigned int audio_subsegments;
84 
85  avio_skip(pb, 3);
86  mtv->file_size = avio_rl32(pb);
87  mtv->segments = avio_rl32(pb);
88  avio_skip(pb, 32);
89  mtv->audio_identifier = avio_rl24(pb);
90  mtv->audio_br = avio_rl16(pb);
91  mtv->img_colorfmt = avio_rl24(pb);
92  mtv->img_bpp = avio_r8(pb);
93  mtv->img_width = avio_rl16(pb);
94  mtv->img_height = avio_rl16(pb);
95  mtv->img_segment_size = avio_rl16(pb);
96 
97  /* Calculate width and height if missing from header */
98 
99  if(mtv->img_bpp>>3){
100  if(!mtv->img_width && mtv->img_height)
101  mtv->img_width=mtv->img_segment_size / (mtv->img_bpp>>3)
102  / mtv->img_height;
103 
104  if(!mtv->img_height && mtv->img_width)
105  mtv->img_height=mtv->img_segment_size / (mtv->img_bpp>>3)
106  / mtv->img_width;
107  }
108  if(!mtv->img_height || !mtv->img_width || !mtv->img_segment_size){
109  av_log(s, AV_LOG_ERROR, "width or height or segment_size is invalid and I cannot calculate them from other information\n");
110  return AVERROR(EINVAL);
111  }
112 
113  avio_skip(pb, 4);
114  audio_subsegments = avio_rl16(pb);
115 
116  if (audio_subsegments == 0) {
117  avpriv_request_sample(s, "MTV files without audio");
118  return AVERROR_PATCHWELCOME;
119  }
120 
121  mtv->full_segment_size =
122  audio_subsegments * (MTV_AUDIO_PADDING_SIZE + MTV_ASUBCHUNK_DATA_SIZE) +
123  mtv->img_segment_size;
124  mtv->video_fps = (mtv->audio_br / 4) / audio_subsegments;
125 
126  // FIXME Add sanity check here
127 
128  // all systems go! init decoders
129 
130  // video - raw rgb565
131 
132  st = avformat_new_stream(s, NULL);
133  if(!st)
134  return AVERROR(ENOMEM);
135 
136  avpriv_set_pts_info(st, 64, 1, mtv->video_fps);
140  st->codec->width = mtv->img_width;
141  st->codec->height = mtv->img_height;
142  st->codec->sample_rate = mtv->video_fps;
143  st->codec->extradata = av_strdup("BottomUp");
144  st->codec->extradata_size = 9;
145 
146  // audio - mp3
147 
148  st = avformat_new_stream(s, NULL);
149  if(!st)
150  return AVERROR(ENOMEM);
151 
155  st->codec->bit_rate = mtv->audio_br;
157 
158  // Jump over header
159 
160  if(avio_seek(pb, MTV_HEADER_SIZE, SEEK_SET) != MTV_HEADER_SIZE)
161  return AVERROR(EIO);
162 
163  return 0;
164 
165 }
166 
168 {
169  MTVDemuxContext *mtv = s->priv_data;
170  AVIOContext *pb = s->pb;
171  int ret;
172 
173  if((avio_tell(pb) - s->data_offset + mtv->img_segment_size) % mtv->full_segment_size)
174  {
176 
177  ret = av_get_packet(pb, pkt, MTV_ASUBCHUNK_DATA_SIZE);
178  if(ret < 0)
179  return ret;
180 
181  pkt->pos -= MTV_AUDIO_PADDING_SIZE;
182  pkt->stream_index = 1;
183 
184  }else
185  {
186  ret = av_get_packet(pb, pkt, mtv->img_segment_size);
187  if(ret < 0)
188  return ret;
189 
190  pkt->stream_index = 0;
191  }
192 
193  return ret;
194 }
195 
197  .name = "mtv",
198  .long_name = NULL_IF_CONFIG_SMALL("MTV"),
199  .priv_data_size = sizeof(MTVDemuxContext),
203 };