f = fopen(filename, "w");
f = fopen(filename, "wb");
void video_encode_example(const char *filename){    AVCodec *codec;    AVCodecContext *c= NULL;    int i, out_size, size, x, y, outbuf_size;    FILE *f;    AVFrame *picture;    uint8_t *outbuf, *picture_buf;    printf("Video encoding\n");    /* find the mpeg1 video encoder */    codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);    if (!codec) {        fprintf(stderr, "codec not found\n");        exit(1);    }    c= avcodec_alloc_context();    picture= avcodec_alloc_frame();        /* put sample parameters */    c->bit_rate = 400000;    /* resolution must be a multiple of two */    c->width = 352;      c->height = 288;    /* frames per second */    c->frame_rate = 25;      c->frame_rate_base= 1;    c->gop_size = 10; /* emit one intra frame every ten frames */    c->max_b_frames=1;    /* open it */    if (avcodec_open(c, codec) < 0) {        fprintf(stderr, "could not open codec\n");        exit(1);    }        /* the codec gives us the frame size, in samples */    f = fopen(filename, "w");    if (!f) {        fprintf(stderr, "could not open %s\n", filename);        exit(1);    }        /* alloc image and output buffer */    outbuf_size = 100000;    outbuf = malloc(outbuf_size);    size = c->width * c->height;    picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */        picture->data[0] = picture_buf;    picture->data[1] = picture->data[0] + size;    picture->data[2] = picture->data[1] + size / 4;    picture->linesize[0] = c->width;    picture->linesize[1] = c->width / 2;    picture->linesize[2] = c->width / 2;    /* encode 1 second of video */    for(i=0;i<25;i++) {        fflush(stdout);        /* prepare a dummy image */        /* Y */        for(y=0;y<c->height;y++) {            for(x=0;x<c->width;x++) {                picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;            }        }        /* Cb and Cr */        for(y=0;y<c->height/2;y++) {            for(x=0;x<c->width/2;x++) {                picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;                picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;            }        }        /* encode the image */        out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);        printf("encoding frame %3d (size=%5d)\n", i, out_size);        fwrite(outbuf, 1, out_size, f);    }    /* get the delayed frames */    for(; out_size; i++) {        fflush(stdout);                out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);        printf("write frame %3d (size=%5d)\n", i, out_size);        fwrite(outbuf, 1, out_size, f);    }    /* add sequence end code to have a real mpeg file */    outbuf[0] = 0x00;    outbuf[1] = 0x00;    outbuf[2] = 0x01;    outbuf[3] = 0xb7;    fwrite(outbuf, 1, 4, f);    fclose(f);    free(picture_buf);    free(outbuf);    avcodec_close(c);    free(c);    free(picture);    printf("\n");}