8a735d0ba9
This improves a stereo (front-left + front-right) sound "image" by generating a front-center channel signal. Done correctly, it helps reduce the comb effects and phase errors associated with using only two speakers to simulate center sounds. Note that it shouldn't be used if the front-center channel is already included in the positional audio mix (the dialog effect is okay). In general, it may actually be better to exclude the front-center channel from the positional audio mix and use this to generate front-center output.
84 lines
3.0 KiB
C
84 lines
3.0 KiB
C
#ifndef BFORMATDEC_H
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#define BFORMATDEC_H
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#include "alMain.h"
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/* These are the necessary scales for first-order HF responses to play over
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* higher-order 2D (non-periphonic) decoders.
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*/
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#define W_SCALE2D_SECOND 1.224744871f /* sqrt(1.5) */
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#define XYZ_SCALE2D_SECOND 1.0f
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#define W_SCALE2D_THIRD 1.414213562f /* sqrt(2) */
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#define XYZ_SCALE2D_THIRD 1.082392196f
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/* These are the necessary scales for first-order HF responses to play over
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* higher-order 3D (periphonic) decoders.
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*/
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#define W_SCALE3D_SECOND 1.341640787f /* sqrt(1.8) */
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#define XYZ_SCALE3D_SECOND 1.0f
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#define W_SCALE3D_THIRD 1.695486018f
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#define XYZ_SCALE3D_THIRD 1.136697713f
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struct AmbDecConf;
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struct BFormatDec;
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struct AmbiUpsampler;
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struct BFormatDec *bformatdec_alloc();
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void bformatdec_free(struct BFormatDec *dec);
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void bformatdec_reset(struct BFormatDec *dec, const struct AmbDecConf *conf, ALsizei chancount, ALuint srate, const ALsizei chanmap[MAX_OUTPUT_CHANNELS]);
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/* Decodes the ambisonic input to the given output channels. */
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void bformatdec_process(struct BFormatDec *dec, ALfloat (*restrict OutBuffer)[BUFFERSIZE], ALsizei OutChannels, const ALfloat (*restrict InSamples)[BUFFERSIZE], ALsizei SamplesToDo);
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/* Up-samples a first-order input to the decoder's configuration. */
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void bformatdec_upSample(struct BFormatDec *dec, ALfloat (*restrict OutBuffer)[BUFFERSIZE], const ALfloat (*restrict InSamples)[BUFFERSIZE], ALsizei InChannels, ALsizei SamplesToDo);
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/* Stand-alone first-order upsampler. Kept here because it shares some stuff
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* with bformatdec.
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*/
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struct AmbiUpsampler *ambiup_alloc();
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void ambiup_free(struct AmbiUpsampler *ambiup);
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void ambiup_reset(struct AmbiUpsampler *ambiup, const ALCdevice *device);
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void ambiup_process(struct AmbiUpsampler *ambiup, ALfloat (*restrict OutBuffer)[BUFFERSIZE], ALsizei OutChannels, const ALfloat (*restrict InSamples)[BUFFERSIZE], ALsizei SamplesToDo);
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/* Band splitter. Splits a signal into two phase-matching frequency bands. */
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typedef struct BandSplitter {
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ALfloat coeff;
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ALfloat lp_z1;
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ALfloat lp_z2;
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ALfloat hp_z1;
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} BandSplitter;
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void bandsplit_init(BandSplitter *splitter, ALfloat freq_mult);
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void bandsplit_clear(BandSplitter *splitter);
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void bandsplit_process(BandSplitter *splitter, ALfloat *restrict hpout, ALfloat *restrict lpout,
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const ALfloat *input, ALsizei count);
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/* The all-pass portion of the band splitter. Applies the same phase shift
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* without splitting the signal.
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*/
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typedef struct SplitterAllpass {
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ALfloat coeff;
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ALfloat z1;
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} SplitterAllpass;
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void splitterap_init(SplitterAllpass *splitter, ALfloat freq_mult);
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void splitterap_clear(SplitterAllpass *splitter);
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void splitterap_process(SplitterAllpass *splitter, ALfloat *restrict samples, ALsizei count);
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typedef struct FrontStablizer {
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SplitterAllpass APFilter[MAX_OUTPUT_CHANNELS];
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BandSplitter LFilter, RFilter;
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alignas(16) ALfloat LSplit[2][BUFFERSIZE];
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alignas(16) ALfloat RSplit[2][BUFFERSIZE];
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} FrontStablizer;
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#endif /* BFORMATDEC_H */
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