MS GSM610 WAV49

[mgarrettcallcopy_com]

Hello. I'm trying to encode a raw PCM stream into GSM610. The library works great except I'm not seeing an option for encoding for encoding to wav49 microsoft version of gsm610 (40ms blocks, 65 bytes, 320 samples). Is there anyway to do this?

[Igor_B_Intel1 · Accepted solution]

Hi,
Yes, it is possible with little trick because MS GSM610 has got own bitstream format.
GSM FR according to the official codec specification provide bitstream in the size of 33 bytes for one frame. First 4 bits of bitstream represents gsm frame ID. It can be 0x0h or 0xDh. To form one frame (or block) for MS GSM610 in the length os 65 you should throw away these 4 bits from two GSM FR frames and concatenate them (on bit level without gap). Hence from 66 bytes of two GSM FR frames you will get 65 bytesfor one MS GSM610 block.

Igor S. Belyakov

[mgarrettcallcopy_com]

That is exactly what I needed. Thanks for your clear reply ;)