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decode voice data with G.722.1 Annex C

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decode voice data with G.722.1 Annex C

Afternoon, We have video conference system and do some voice test which encode/decode with G.722.1_C(Siren 14), the transmission rate is 48kbit/s,We capture all voice UDP/RTP packets transmiting from remote device  and extract pure voice signal (120byte per 20ms)saving as a file.then We decode the file  to PCM format signal(the  decoder We download for ITU websit,by the ITU-R Rec.G.722.1"Coding at 24 and 32 kbit/s for hands-free operation in systems with low frame loss "),but the PCM file is just noise sigal, explorering the file, We find almost every byte of the file is "00". why happened like this ? what the format when store G.722.1_C  signal?  Thanks!
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