int write_vorbis_comment(byte[] comment, int pos, int last)
{
BitWriter bitwriter = new BitWriter(comment, pos, 4);
Encoding enc = new ASCIIEncoding();
int vendor_len = enc.GetBytes(vendor_string, 0, vendor_string.Length, comment, pos + 8);
// metadata header
bitwriter.writebits(1, last);
bitwriter.writebits(7, (int)MetadataType.VorbisComment);
bitwriter.writebits(24, vendor_len + 8);
comment[pos + 4] = (byte)(vendor_len & 0xFF);
comment[pos + 5] = (byte)((vendor_len >> 8) & 0xFF);
comment[pos + 6] = (byte)((vendor_len >> 16) & 0xFF);
comment[pos + 7] = (byte)((vendor_len >> 24) & 0xFF);
comment[pos + 8 + vendor_len] = 0;
comment[pos + 9 + vendor_len] = 0;
comment[pos + 10 + vendor_len] = 0;
comment[pos + 11 + vendor_len] = 0;
bitwriter.flush();
return vendor_len + 12;
}