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bit.c
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1 /*
2  * G.729 bit format muxer and demuxer
3  * Copyright (c) 2007-2008 Vladimir Voroshilov
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 #include "avformat.h"
22 #include "internal.h"
23 #include "libavcodec/get_bits.h"
24 #include "libavcodec/put_bits.h"
25 
26 #define MAX_FRAME_SIZE 10
27 
28 #define SYNC_WORD 0x6b21
29 #define BIT_0 0x7f
30 #define BIT_1 0x81
31 
32 static int probe(AVProbeData *p)
33 {
34  int i, j;
35 
36  if(p->buf_size < 0x40)
37  return 0;
38 
39  for(i=0; i+3<p->buf_size && i< 10*0x50; ){
40  if(AV_RL16(&p->buf[0]) != SYNC_WORD)
41  return 0;
42  j=AV_RL16(&p->buf[2]);
43  if(j!=0x40 && j!=0x50)
44  return 0;
45  i+=j;
46  }
47  return AVPROBE_SCORE_MAX/2;
48 }
49 
51 {
52  AVStream* st;
53 
55  if (!st)
56  return AVERROR(ENOMEM);
57 
60  st->codec->sample_rate=8000;
61  st->codec->block_align = 16;
62  st->codec->channels=1;
63 
64  avpriv_set_pts_info(st, 64, 1, 100);
65  return 0;
66 }
67 
69  AVPacket *pkt)
70 {
71  AVIOContext *pb = s->pb;
72  PutBitContext pbo;
73  uint16_t buf[8 * MAX_FRAME_SIZE + 2];
74  int packet_size;
75  uint16_t* src=buf;
76  int i, j, ret;
77  int64_t pos= avio_tell(pb);
78 
79  if(url_feof(pb))
80  return AVERROR_EOF;
81 
82  avio_rl16(pb); // sync word
83  packet_size = avio_rl16(pb) / 8;
84  if(packet_size > MAX_FRAME_SIZE)
85  return AVERROR_INVALIDDATA;
86 
87  ret = avio_read(pb, (uint8_t*)buf, (8 * packet_size) * sizeof(uint16_t));
88  if(ret<0)
89  return ret;
90  if(ret != 8 * packet_size * sizeof(uint16_t))
91  return AVERROR(EIO);
92 
93  if (av_new_packet(pkt, packet_size) < 0)
94  return AVERROR(ENOMEM);
95 
96  init_put_bits(&pbo, pkt->data, packet_size);
97  for(j=0; j < packet_size; j++)
98  for(i=0; i<8;i++)
99  put_bits(&pbo,1, AV_RL16(src++) == BIT_1 ? 1 : 0);
100 
101  flush_put_bits(&pbo);
102 
103  pkt->duration=1;
104  pkt->pos = pos;
105  return 0;
106 }
107 
109  .name = "bit",
110  .long_name = NULL_IF_CONFIG_SMALL("G.729 BIT file format"),
111  .read_probe = probe,
112  .read_header = read_header,
113  .read_packet = read_packet,
114  .extensions = "bit",
115 };
116 
117 #if CONFIG_MUXERS
118 static int write_header(AVFormatContext *s)
119 {
120  AVCodecContext *enc = s->streams[0]->codec;
121 
122  enc->codec_id = AV_CODEC_ID_G729;
123  enc->channels = 1;
124  enc->bits_per_coded_sample = 16;
125  enc->block_align = (enc->bits_per_coded_sample * enc->channels) >> 3;
126 
127  return 0;
128 }
129 
130 static int write_packet(AVFormatContext *s, AVPacket *pkt)
131 {
132  AVIOContext *pb = s->pb;
133  GetBitContext gb;
134  int i;
135 
136  avio_wl16(pb, SYNC_WORD);
137  avio_wl16(pb, 8 * 10);
138 
139  init_get_bits(&gb, pkt->data, 8*10);
140  for(i=0; i< 8 * 10; i++)
141  avio_wl16(pb, get_bits1(&gb) ? BIT_1 : BIT_0);
142  avio_flush(pb);
143 
144  return 0;
145 }
146 
147 AVOutputFormat ff_bit_muxer = {
148  .name = "bit",
149  .long_name = NULL_IF_CONFIG_SMALL("G.729 BIT file format"),
150  .mime_type = "audio/bit",
151  .extensions = "bit",
152  .audio_codec = AV_CODEC_ID_G729,
153  .video_codec = AV_CODEC_ID_NONE,
154  .write_header = write_header,
155  .write_packet = write_packet,
156 };
157 #endif