do rescaling for each conversion individually (1f9fadfc) · Commits · IVAS Codec Public Collaboration / IVAS Codec

lib_util/ambi_convert.c

+19 −28

Original line number	Diff line number	Diff line
		@@ -55,18 +55,8 @@
		#define INV_SQRT_3_OVER_5_ 1.2909944f
		#define INV_SQRT_45_OVER_32_ 0.8432740f

		#define INV_SQRT_FOUR_PI_ 0.2820947f /* 1/sqrt(4/pi) */

		#define AMBI_MAX_CHANNELS 16

		/*
		For conversions to SN3D we want to avoid clipping the decoder input.
		The GLOBAL_SCALING_FACTOR ensures that the amplitude is always attenuated.
		The inverse INV_GLOBAL_SCALING_FACTOR restores the original amplitude when
		converting back to the input convention after the decoding.
		*/
		#define GLOBAL_SCALING_FACTOR 0.7071067f
		#define INV_GLOBAL_SCALING_FACTOR 0.7071067f

		/* --------------------------------
		normalization conversion tables
		@@ -82,6 +72,8 @@ static const float N3D_SN3D[AMBI_MAX_CHANNELS] = { 1.0f,
		INV_SQRT_5_, INV_SQRT_5_, INV_SQRT_5_, INV_SQRT_5_, INV_SQRT_5_,
		INV_SQRT_7_, INV_SQRT_7_, INV_SQRT_7_, INV_SQRT_7_, INV_SQRT_7_, INV_SQRT_7_, INV_SQRT_7_ };

		static const float N3D_SCALING_FACTOR = 1.0f;


		static const float SN3D_MAXN[AMBI_MAX_CHANNELS] = { 1.0f,
		1.0f, 1.0f, 1.0f,
		@@ -93,6 +85,8 @@ static const float MAXN_SN3D[AMBI_MAX_CHANNELS] = { 1.0f,
		INV_TWO_OVER_SQRT_3_, INV_TWO_OVER_SQRT_3_, 1.0f, INV_TWO_OVER_SQRT_3_, INV_TWO_OVER_SQRT_3_,
		INV_SQRT_8_OVER_5_, INV_SQRT_3_OVER_5_, INV_SQRT_45_OVER_32_, 1.0f, INV_SQRT_45_OVER_32_, INV_SQRT_3_OVER_5_, INV_SQRT_8_OVER_5_ };

		static const float MAXN_SCALING_FACTOR = SQRT_3_OVER_5_;


		static const float SN3D_FM[AMBI_MAX_CHANNELS] = { INV_SQRT_2,
		1.0f, 1.0f, 1.0f,
		@@ -104,6 +98,9 @@ static const float FM_SN3D[AMBI_MAX_CHANNELS] = { SQRT_2_,
		INV_TWO_OVER_SQRT_3_, INV_TWO_OVER_SQRT_3_, 1.0f, INV_TWO_OVER_SQRT_3_, INV_TWO_OVER_SQRT_3_,
		INV_SQRT_8_OVER_5_, INV_SQRT_3_OVER_5_, INV_SQRT_45_OVER_32_, 1.0f, INV_SQRT_45_OVER_32_, INV_SQRT_3_OVER_5_, INV_SQRT_8_OVER_5_ };

		static const float FM_SCALING_FACTOR = INV_SQRT_2;


		/* ----------------------------
		channel re-ordering tables
		---------------------------- */
		@@ -199,6 +196,7 @@ int16_t renormalize_channels( float in[], float out[], int16_t order, AMBI_CHA
		int16_t n_chan = ( order + 1 ) * ( order + 1 );
		int16_t i_chan, i;
		const float *conversion_table = 0;
		float sf = 1.0f;

		/* conversion factors are aplpied on the channels assuming that they are still/already in ACN order */

		@@ -207,14 +205,17 @@ int16_t renormalize_channels( float in[], float out[], int16_t order, AMBI_CHA
		if ( out_format == AMBI_NORM_N3D )
		{
		conversion_table = SN3D_N3D;
		sf = 1.f / N3D_SCALING_FACTOR;
		}
		else if ( out_format == AMBI_NORM_MAXN )
		{
		conversion_table = SN3D_MAXN;
		sf = 1.f / MAXN_SCALING_FACTOR;
		}
		else if ( out_format == AMBI_NORM_FM )
		{
		conversion_table = SN3D_FM;
		sf = 1.f / FM_SCALING_FACTOR;
		}
		else
		{
		@@ -226,14 +227,17 @@ int16_t renormalize_channels( float in[], float out[], int16_t order, AMBI_CHA
		if ( in_format == AMBI_NORM_N3D )
		{
		conversion_table = N3D_SN3D;
		sf = N3D_SCALING_FACTOR;
		}
		else if ( in_format == AMBI_NORM_MAXN )
		{
		conversion_table = MAXN_SN3D;
		sf = MAXN_SCALING_FACTOR;
		}
		else if ( in_format == AMBI_NORM_FM )
		{
		conversion_table = FM_SN3D;
		sf = FM_SCALING_FACTOR;
		}
		else
		{
		@@ -245,26 +249,13 @@ int16_t renormalize_channels( float in[], float out[], int16_t order, AMBI_CHA
		assert( 0 && "Conversion only supported to and from ACN-SN3D" );
		}

		if ( out_format == AMBI_NORM_SN3D )
		{
		for ( i_chan = 0; i_chan < n_chan; i_chan++ )
		{
		float conversion_factor = conversion_table[i_chan];
		for ( i = 0; i < L_FRAME48k; i++ )
		{
		out[i_chan][i] = GLOBAL_SCALING_FACTOR * in[i_chan][i] * conversion_factor;
		}
		}
		}
		else
		{

		for ( i_chan = 0; i_chan < n_chan; i_chan++ )
		{
		float conversion_factor = conversion_table[i_chan];
		for ( i = 0; i < L_FRAME48k; i++ )
		{
		out[i_chan][i] = INV_GLOBAL_SCALING_FACTOR * in[i_chan][i] * conversion_factor;
		}
		out[i_chan][i] = sf * in[i_chan][i] * conversion_factor;
		}
		}