o->format->data(o, filter_out, filter_out_len, &output_buf, &output_len);
if (output_buf) {
fwrite(output_buf, 1, output_len, outfile);
o->format->data(o, filter_out, filter_out_len, &output_buf, &output_len);
if (output_buf) {
fwrite(output_buf, 1, output_len, outfile);