snprintf(filename, sizeof(filename), s->path, s->img_number);
if (get_frame_filename(filename, sizeof(filename), s->path, s->img_number) < 0) return -EIO;
static int jpeg_read_packet(AVFormatContext *s1, AVPacket *pkt){    JpegContext *s = s1->priv_data;    char filename[1024];    int size;    ByteIOContext f1, *f = &f1;    snprintf(filename, sizeof(filename), s->path, s->img_number);        f = &f1;    if (url_fopen(f, filename, URL_RDONLY) < 0)        return -EIO;        size = url_seek(url_fileno(f), 0, SEEK_END);    url_seek(url_fileno(f), 0, SEEK_SET);    av_new_packet(pkt, size);    pkt->stream_index = 0;    get_buffer(f, pkt->data, size);    url_fclose(f);    s->img_number++;    return 0;}