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.

/*
 * In the original 3GPP code, the selection between VAD1 and VAD2 is made
 * only at compile time.  In libtwamr we support run-time selection between
 * these two VAD algorithms for tinkering and investigation work; this
 * header file implements the logic that fits this run-time selection
 * into the existing code structure from 3GPP.
 */

#ifndef	vad_h
#define	vad_h

#include "typedef.h"
#include "vad1.h"
#include "vad2.h"

typedef struct {
	Flag	use_vad2;
	union {
		vadState1	v1;
		vadState2	v2;
	} u;
} vadState;

void vad_reset(vadState *st, Flag use_vad2);

#endif	/* include guard */