About speech decode...

Dear All.. Finally I can use OSMOCOM-Tetra to decode some Tetra signal by Wireshark. But I have met some problems when speech decode the files on the mailing list. 1. It's always show "0 Channel Frames processed ie 0 Speech Frame" message when I input a bits file(whatever converting from OSMOCOM-Tetra or download from the mailing list providing) to "cdecoder" program.(Of course it will output a useless "blank file".) 2. I tried to input the sample bits files into "sdecoder" program and it can convert a PCM file. If I use some playback programs include aplay(-f S16_LE) to play the PCM file, there's no any readable speech. Does anyone can help me to check this? I don't know what point I missed. Thank a lot! Best Regards Eddy.