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
25  * video decoding with libavcodec API example
26  *
27  * @example decode_video.c
28  */
29 
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33 
34 #include <libavcodec/avcodec.h>
35 
36 #define INBUF_SIZE 4096
37 
38 static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize,
39  char *filename)
40 {
41  FILE *f;
42  int i;
43 
44  f = fopen(filename,"wb");
45  fprintf(f, "P5\n%d %d\n%d\n", xsize, ysize, 255);
46  for (i = 0; i < ysize; i++)
47  fwrite(buf + i * wrap, 1, xsize, f);
48  fclose(f);
49 }
50 
52  const char *filename)
53 {
54  char buf[1024];
55  int ret;
56 
58  if (ret < 0) {
59  fprintf(stderr, "Error sending a packet for decoding\n");
60  exit(1);
61  }
62 
63  while (ret >= 0) {
65  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
66  return;
67  else if (ret < 0) {
68  fprintf(stderr, "Error during decoding\n");
69  exit(1);
70  }
71 
72  printf("saving frame %3d\n", dec_ctx->frame_number);
73  fflush(stdout);
74 
75  /* the picture is allocated by the decoder. no need to
76  free it */
77  snprintf(buf, sizeof(buf), "%s-%d", filename, dec_ctx->frame_number);
78  pgm_save(frame->data[0], frame->linesize[0],
79  frame->width, frame->height, buf);
80  }
81 }
82 
83 int main(int argc, char **argv)
84 {
85  const char *filename, *outfilename;
86  const AVCodec *codec;
87  AVCodecParserContext *parser;
89  FILE *f;
90  AVFrame *frame;
92  uint8_t *data;
93  size_t data_size;
94  int ret;
95  int eof;
96  AVPacket *pkt;
97 
98  if (argc <= 2) {
99  fprintf(stderr, "Usage: %s <input file> <output file>\n"
100  "And check your input file is encoded by mpeg1video please.\n", argv[0]);
101  exit(0);
102  }
103  filename = argv[1];
104  outfilename = argv[2];
105 
106  pkt = av_packet_alloc();
107  if (!pkt)
108  exit(1);
109 
110  /* set end of buffer to 0 (this ensures that no overreading happens for damaged MPEG streams) */
111  memset(inbuf + INBUF_SIZE, 0, AV_INPUT_BUFFER_PADDING_SIZE);
112 
113  /* find the MPEG-1 video decoder */
115  if (!codec) {
116  fprintf(stderr, "Codec not found\n");
117  exit(1);
118  }
119 
120  parser = av_parser_init(codec->id);
121  if (!parser) {
122  fprintf(stderr, "parser not found\n");
123  exit(1);
124  }
125 
126  c = avcodec_alloc_context3(codec);
127  if (!c) {
128  fprintf(stderr, "Could not allocate video codec context\n");
129  exit(1);
130  }
131 
132  /* For some codecs, such as msmpeg4 and mpeg4, width and height
133  MUST be initialized there because this information is not
134  available in the bitstream. */
135 
136  /* open it */
137  if (avcodec_open2(c, codec, NULL) < 0) {
138  fprintf(stderr, "Could not open codec\n");
139  exit(1);
140  }
141 
142  f = fopen(filename, "rb");
143  if (!f) {
144  fprintf(stderr, "Could not open %s\n", filename);
145  exit(1);
146  }
147 
148  frame = av_frame_alloc();
149  if (!frame) {
150  fprintf(stderr, "Could not allocate video frame\n");
151  exit(1);
152  }
153 
154  do {
155  /* read raw data from the input file */
156  data_size = fread(inbuf, 1, INBUF_SIZE, f);
157  if (ferror(f))
158  break;
159  eof = !data_size;
160 
161  /* use the parser to split the data into frames */
162  data = inbuf;
163  while (data_size > 0 || eof) {
164  ret = av_parser_parse2(parser, c, &pkt->data, &pkt->size,
165  data, data_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
166  if (ret < 0) {
167  fprintf(stderr, "Error while parsing\n");
168  exit(1);
169  }
170  data += ret;
171  data_size -= ret;
172 
173  if (pkt->size)
174  decode(c, frame, pkt, outfilename);
175  else if (eof)
176  break;
177  }
178  } while (!eof);
179 
180  /* flush the decoder */
181  decode(c, frame, NULL, outfilename);
182 
183  fclose(f);
184 
185  av_parser_close(parser);
189 
190  return 0;
191 }
AVCodec
AVCodec.
Definition: codec.h:204
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
AVERROR_EOF
#define AVERROR_EOF
End of file.
Definition: error.h:57
av_frame_free
void av_frame_free(AVFrame **frame)
Free the frame and any dynamically allocated objects in it, e.g.
Definition: frame.c:116
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:325
AVPacket::data
uint8_t * data
Definition: packet.h:374
pgm_save
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, char *filename)
Definition: decode_video.c:38
data
const char data[16]
Definition: mxf.c:146
av_packet_free
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: avpacket.c:73
wrap
#define wrap(func)
Definition: neontest.h:65
av_parser_init
AVCodecParserContext * av_parser_init(int codec_id)
Definition: parser.c:32
av_frame_alloc
AVFrame * av_frame_alloc(void)
Allocate an AVFrame and set its fields to default values.
Definition: frame.c:104
pkt
AVPacket * pkt
Definition: movenc.c:59
avcodec_alloc_context3
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
Definition: options.c:149
avcodec_receive_frame
int attribute_align_arg 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...
Definition: avcodec.c:719
decode
static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt, const char *filename)
Definition: decode_video.c:51
NULL
#define NULL
Definition: coverity.c:32
avcodec_free_context
void avcodec_free_context(AVCodecContext **avctx)
Free the codec context and everything associated with it and write NULL to the provided pointer.
Definition: options.c:164
avcodec_open2
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
Definition: avcodec.c:115
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
AV_CODEC_ID_MPEG1VIDEO
@ AV_CODEC_ID_MPEG1VIDEO
Definition: codec_id.h:53
avcodec_find_decoder
const AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
Definition: allcodecs.c:951
f
f
Definition: af_crystalizer.c:122
AVPacket::size
int size
Definition: packet.h:375
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
printf
printf("static const uint8_t my_array[100] = {\n")
av_packet_alloc
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:62
AVCodec::id
enum AVCodecID id
Definition: codec.h:218
avcodec_send_packet
int avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
Supply raw packet data as input to a decoder.
Definition: decode.c:637
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:269
avcodec.h
AVCodecParserContext
Definition: avcodec.h:2800
ret
ret
Definition: filter_design.txt:187
frame
these buffered frames must be flushed immediately if a new input produces new the filter must not call request_frame to get more It must just process the frame or queue it The task of requesting more frames is left to the filter s request_frame method or the application If a filter has several the filter must be ready for frames arriving randomly on any input any filter with several inputs will most likely require some kind of queuing mechanism It is perfectly acceptable to have a limited queue and to drop frames when the inputs are too unbalanced request_frame For filters that do not use the this method is called when a frame is wanted on an output For a it should directly call filter_frame on the corresponding output For a if there are queued frames already one of these frames should be pushed If the filter should request a frame on one of its repeatedly until at least one frame has been pushed Return or at least make progress towards producing a frame
Definition: filter_design.txt:264
AV_INPUT_BUFFER_PADDING_SIZE
#define AV_INPUT_BUFFER_PADDING_SIZE
Definition: defs.h:40
AVCodecContext
main external API structure.
Definition: avcodec.h:398
av_parser_parse2
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.
Definition: parser.c:115
AVCodecContext::frame_number
int frame_number
Frame counter, set by libavcodec.
Definition: avcodec.h:1046
AVPacket
This structure stores compressed data.
Definition: packet.h:351
main
int main(int argc, char **argv)
Definition: decode_video.c:83
snprintf
#define snprintf
Definition: snprintf.h:34
INBUF_SIZE
#define INBUF_SIZE
Definition: decode_video.c:36
dec_ctx
static AVCodecContext * dec_ctx
Definition: filtering_audio.c:44
av_parser_close
void av_parser_close(AVCodecParserContext *s)
Definition: parser.c:189