always attenuate the signal when converting to SN3D (b958e6f0) · Commits · IVAS Codec Public Collaboration / IVAS Codec

lib_util/ambi_convert.c

+27 −4

Original line number	Diff line number	Diff line
		@@ -59,6 +59,15 @@

		#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
		-------------------------------- */
		@@ -236,12 +245,26 @@ 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] = in[i_chan][i] * conversion_factor;
		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;
		}
		}
		}