Hello Fabio, On Sun, 01 Aug 2010 16:50:20 +0200, "Fabio Pietrosanti (naif)" <[email protected]> wrote: > > So in theory, but i can be missing something, we can use the AMR header > as known plaintext of every call: > - the 1 byte header describe the sampling bitrate > - we can identify the sampling bitrate by looking at the size of the AMR > 20ms sample
This is not enough because you need the plaintext of a whole BURST. A FRAME (23 bytes) is encoded into four BURSTs (this is true for everything but traffic) and due to how the encoding works, you need to know the whole 23 bytes of a frame, a single byte is not enough. For a Full Rate TCH channel you even need to know the bytes of two FRAMEs because the two frames are encoded into eight BURSTs (for the SACCH of the traffic channel its still four BURSTs per FRAME). Best regards, Dieter -- Dieter Spaar, Germany [email protected] _______________________________________________ A51 mailing list [email protected] http://lists.lists.reflextor.com/cgi-bin/mailman/listinfo/a51
