FFmpeg 7.1.1
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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
39static 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);
80 frame->width, frame->height, buf);
81 }
82}
83
84int main(int argc, char **argv)
85{
86 const char *filename, *outfilename;
87 const AVCodec *codec;
89 AVCodecContext *c= NULL;
90 FILE *f;
93 uint8_t *data;
94 size_t data_size;
95 int ret;
96 int eof;
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
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
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.
int main(int argc, char *argv[])
static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame, FILE *outfile)
static AVCodecContext * dec_ctx
#define INBUF_SIZE
static void pgm_save(unsigned char *buf, int wrap, int xsize, int ysize, char *filename)
static AVPacket * pkt
static AVFrame * frame
int avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
Initialize the AVCodecContext to use the given AVCodec.
AVCodecContext * avcodec_alloc_context3(const AVCodec *codec)
Allocate an AVCodecContext and set its fields to default values.
const AVCodec * avcodec_find_decoder(enum AVCodecID id)
Find a registered decoder with a matching codec ID.
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.
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.
AVCodecParserContext * av_parser_init(int codec_id)
#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:451
int64_t frame_num
Frame counter, set by libavcodec.
Definition avcodec.h:2041
AVCodec.
Definition codec.h:187
enum AVCodecID id
Definition codec.h:201
This structure describes decoded (raw) audio or video data.
Definition frame.h:389
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition frame.h:410
int width
Definition frame.h:461
int height
Definition frame.h:461
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:434
This structure stores compressed data.
Definition packet.h:516
int size
Definition packet.h:540
uint8_t * data
Definition packet.h:539