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
38static 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
51static void decode(AVCodecContext *dec_ctx, AVFrame *frame, AVPacket *pkt,
52                   const char *filename)
53{
54    char buf[1024];
55    int ret;
56
57    ret = avcodec_send_packet(dec_ctx, pkt);
58    if (ret < 0) {
59        fprintf(stderr, "Error sending a packet for decoding\n");
60        exit(1);
61    }
62
63    while (ret >= 0) {
64        ret = avcodec_receive_frame(dec_ctx, frame);
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
83int main(int argc, char **argv)
84{
85    const char *filename, *outfilename;
86    const AVCodec *codec;
87    AVCodecParserContext *parser;
88    AVCodecContext *c= NULL;
89    FILE *f;
90    AVFrame *frame;
91    uint8_t inbuf[INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
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 */
114    codec = avcodec_find_decoder(AV_CODEC_ID_MPEG1VIDEO);
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);
186    avcodec_free_context(&c);
187    av_frame_free(&frame);
188    av_packet_free(&pkt);
189
190    return 0;
191}
192