FFmpeg
decode_video.c
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1 /*
2  * Copyright (c) 2001 Fabrice Bellard
3  *
4  * Permission is hereby granted, free of charge, to any person obtaining a copy
5  * of this software and associated documentation files (the "Software"), to deal
6  * in the Software without restriction, including without limitation the rights
7  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8  * copies of the Software, and to permit persons to whom the Software is
9  * furnished to do so, subject to the following conditions:
10  *
11  * The above copyright notice and this permission notice shall be included in
12  * all copies or substantial portions of the Software.
13  *
14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
17  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20  * THE SOFTWARE.
21  */
22 
23 /**
24  * @file libavcodec video decoding API usage example
25  * @example decode_video.c *
26  *
27  * Read from an MPEG1 video file, decode frames, and generate PGM images as
28  * output.
29  */
30 
31 #include <stdio.h>
32 #include <stdlib.h>
33 #include <string.h>
34 
35 #include <libavcodec/avcodec.h>
36 
37 #define INBUF_SIZE 4096
38 
39 static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
40  char *filename)
41 {
42  FILE *f;
43  int i;
44 
45  f = fopen(filename,"wb");
46  fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
47  for (i = 0; i < ysize; i++)
48  fwrite(buf + i * wrap, 1, xsize, f);
49  fclose(f);
50 }
51 
53  const char *filename)
54 {
55  char buf[1024];
56  int ret;
57 
59  if (ret < 0) {
60  fprintf(stderr, "Error sending a packet for decoding\n");
61  exit(1);
62  }
63 
64  while (ret >= 0) {
66  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
67  return;
68  else if (ret < 0) {
69  fprintf(stderr, "Error during decoding\n");
70  exit(1);
71  }
72 
73  printf("saving frame %3"PRId64"\n", dec_ctx->frame_num);
74  fflush(stdout);
75 
76  /* the picture is allocated by the decoder. no need to
77  free it */
78  snprintf(buf, sizeof(buf), "%s-%"PRId64, filename, dec_ctx->frame_num);
79  pgm_save(frame->data[0], frame->linesize[0],
80  frame->width, frame->height, buf);
81  }
82 }
83 
84 int main(int argc, char **argv)
85 {
86  const char *filename, *outfilename;
87  const AVCodec *codec;
88  AVCodecParserContext *parser;
89  AVCodecContext *c= NULL;
90  FILE *f;
91  AVFrame *frame;
93  uint8_t *data;
94  size_t data_size;
95  int ret;
96  int eof;
97  AVPacket *pkt;
98 
99  if (argc <= 2) {
100  fprintf(stderr, "Usage: %s <input file> <output file>\n"
101  "And check your input file is encoded by mpeg1video please.\n", argv[0]);
102  exit(0);
103  }
104  filename = argv[1];
105  outfilename = argv[2];
106 
107  pkt = av_packet_alloc();
108  if (!pkt)
109  exit(1);
110 
111  /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
112  memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
113 
114  /* find the MPEG-1 video decoder */
116  if (!codec) {
117  fprintf(stderr, "Codec not found\n");
118  exit(1);
119  }
120 
121  parser = av_parser_init(codec->id);
122  if (!parser) {
123  fprintf(stderr, "parser not found\n");
124  exit(1);
125  }
126 
127  c = avcodec_alloc_context3(codec);
128  if (!c) {
129  fprintf(stderr, "Could not allocate video codec context\n");
130  exit(1);
131  }
132 
133  /* For some codecs, such as msmpeg4 and mpeg4, width and height
134  MUST be initialized there because this information is not
135  available in the bitstream. */
136 
137  /* open it */
138  if (avcodec_open2(c, codec, NULL) < 0) {
139  fprintf(stderr, "Could not open codec\n");
140  exit(1);
141  }
142 
143  f = fopen(filename, "rb");
144  if (!f) {
145  fprintf(stderr, "Could not open %s\n", filename);
146  exit(1);
147  }
148 
149  frame = av_frame_alloc();
150  if (!frame) {
151  fprintf(stderr, "Could not allocate video frame\n");
152  exit(1);
153  }
154 
155  do {
156  /* read raw data from the input file */
157  data_size = fread(inbuf, 1, INBUF_SIZE, f);
158  if (ferror(f))
159  break;
160  eof = !data_size;
161 
162  /* use the parser to split the data into frames */
163  data = inbuf;
164  while (data_size > 0 || eof) {
165  ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
166  data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
167  if (ret < 0) {
168  fprintf(stderr, "Error while parsing\n");
169  exit(1);
170  }
171  data += ret;
172  data_size -= ret;
173 
174  if (pkt->size)
175  decode(c, frame, pkt, outfilename);
176  else if (eof)
177  break;
178  }
179  } while (!eof);
180 
181  /* flush the decoder */
182  decode(c, frame, NULL, outfilename);
183 
184  fclose(f);
185 
186  av_parser_close(parser);
190 
191  return 0;
192 }
Libavcodec external API header.
static AVCodecContext * dec_ctx
int main(int argc, char **argv)
Definition: decode_video.c:84
#define INBUF_SIZE
Definition: decode_video.c:37
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, char *filename)
Definition: decode_video.c:39
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt, const char *filename)
Definition: decode_video.c:52
static AVPacket * pkt
Definition: demux_decode.c:55
static AVFrame * frame
Definition: demux_decode.c:54
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
const AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
@ AV_CODEC_ID_MPEG1VIDEO
Definition: codec_id.h:53
int avcodec_receive_frame(AVCodecContext *avctx, AVFrame *frame)
Return decoded output data from a decoder or encoder (when the AV_CODEC_FLAG_RECON_FRAME flag is used...
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
#define AV_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding.
Definition: defs.h:40
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
AVCodecParserContext * av_parser_init(int codec_id)
void av_parser_close(AVCodecParserContext *s)
int av_parser_parse2(AVCodecParserContext *s, AVCodecContext *avctx, uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size, int64_t pts, int64_t dts, int64_t pos)
Parse a packet.
#define AVERROR_EOF
End of file.
Definition: error.h:57
#define AVERROR(e)
Definition: error.h:45
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
main external API structure.
Definition: avcodec.h:426
int64_t frame_num
Frame counter, set by libavcodec.
Definition: avcodec.h:2065
AVCodec.
Definition: codec.h:184
enum AVCodecID id
Definition: codec.h:198
This structure describes decoded (raw) audio or video data.
Definition: frame.h:330
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: frame.h:351
int width
Definition: frame.h:402
int height
Definition: frame.h:402
int linesize[AV_NUM_DATA_POINTERS]
For video, a positive or negative value, which is typically indicating the size in bytes of each pict...
Definition: frame.h:375
This structure stores compressed data.
Definition: packet.h:351
int size
Definition: packet.h:375
uint8_t * data
Definition: packet.h:374