av_bprint_init(&avbuf, FITS_BLOCK_SIZE, AV_BPRINT_SIZE_UNLIMITED);
while ((ret = is_image(s, fits, &header, &avbuf, &size)) == 0) {
av_bprint_init(&avbuf, FITS_BLOCK_SIZE, AV_BPRINT_SIZE_UNLIMITED);
while ((ret = is_image(s, fits, &header, &avbuf, &size)) == 0) {