libgsmhr1 TFO: require BFI=0 and SID=0 for homing In order for a received frame to be recognized as DHF, we need not only the correct bit pattern, but also BFI=0 and SID=0. The BFI=0 requirement should be obvious, while the SID=0 requirement is needed only for HR codec. With FR and EFR, SID classification comes from the payload bits and no separate check is needed - but in HR we get an out-of-band SID ternary flag. When SID=1, no payload bits are used at all; when SID=2, we use only the first 33 bits of the payload. Therefore, it is proper to conditionalize DHF acceptance on SID=0. We already implemented this logic in the just finished full decoder; now bring TFO code into agreement.

/*
 * EFR_insert_sid_codeword() inserts the 95 bit wide SID codeword into
 * an EFR frame in RTP encoding, normally as part of EFR_encode_frame()
 * processing right after EFR_params2frame().
 */

#include "gsm_efr.h"

void EFR_insert_sid_codeword(uint8_t *frame)
{
	frame[6] |= 0x6F;
	frame[7]  = 0xFF;
	frame[8]  = 0xFF;
	frame[9] |= 0x80;
	frame[12] |= 0x3B;
	frame[13]  = 0xFF;
	frame[14]  = 0xFF;
	frame[15] |= 0xE0;
	frame[19]  = 0xFF;
	frame[20]  = 0xFF;
	frame[21]  = 0xFF;
	frame[25]  = 0xFF;
	frame[26] |= 0xFC;
	frame[27]  = 0xFF;
	frame[28] |= 0xC0;
}