libtwamr encoder: always emit frame->mode = mode; In the original implementation of amr_encode_frame(), the 'mode' member of the output struct was set to 0xFF if the output frame type is TX_NO_DATA. This design was made to mimic the mode field (16-bit word) being set to 0xFFFF (or -1) in 3GPP test sequence format - but nothing actually depends on this struct member being set in any way, and amr_frame_to_tseq() generates the needed 0xFFFF on its own, based on frame->type being equal to TX_NO_DATA. It is simpler and more efficient to always set frame->mode to the actual encoding mode in amr_encode_frame(), and this new behavior has already been documented in doc/AMR-library-API description in anticipation of the present change.

/*
 * 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;
}