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.

/*
 * The function implemented in this module is an aid for AMR-EFR interworking:
 * it is meant to be invoked directly after amr_encode_frame(), it checks
 * the encoder output for MR122 DHF, and if the generated frame exactly
 * matches MR122 DHF, it is changed to GSM-EFR DHF.
 */

#include <stdint.h>
#include <string.h>
#include "tw_amr.h"

void amr_dhf_subst_efr(struct amr_param_frame *frame)
{
	if (frame->type != TX_SPEECH_GOOD)
		return;
	if (frame->mode != MR122)
		return;
	if (memcmp(frame->param, amr_dhf_mr122, AMR_MAX_PRM * sizeof(int16_t)))
		return;
	memcpy(frame->param, amr_dhf_gsmefr, AMR_MAX_PRM * sizeof(int16_t));
}