Hi Kim,

According to my knowledge, the 16 redundancy bits are created from the
CRC and repetition bits.

For more details, please refer to the relevant ETSI/3GPP standard, which
in this case is GSM 05.03.

You can access the specification for example here:

http://www.3gpp.org/ftp/Specs/latest...s/0503-621.zip

I hope this answer is of some value to you.

Regards,
Antti


Kim Hyldgaard wrote:
>
> Hi,
>
> I have a quite specific question. Perhabs somebody with technical insight
> can help me:
>
> The EFR algorithm converts 20 ms. of voice (which would be 160 bytes in
> plain G711 encoding) into 244 bits = 30.5 bytes.
> In the GSM specification however, two additional bytes are added. One byte
> is used to protect the 65 most important bits with a CRC, the other byte is
> used to to add redundancy for 4 selected bits.
> These 4 bits are transmitted in 12 bits repeating each bit two times.
>
> OK - this was the information. Now the question:
>
> How should these redundant bits be treated? In my world redundancy means
> identical. However, I have seen the T68i from SonyEricsson to produce a
> strange pattern - for instance 101 or 110. I think the only valid pattern
> should be 111 or 000.
> Does anybody have a comment? - Or perhabs point me to the right group if
> there's a better forum for my question.
>
> Kind regards and thanks in advance
> Kim Hyldgaard