audio/impl/audio_grc3.h

/*
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/*
 * Copyright (C) 4Front Technologies 1996-2008.
 *
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Purpose: GRC library version 3.1 internal definitions
 *
 * GRC3 is a high quality sample rate conversion module that uses fixed point
 * arithmetic.
 */

#ifndef AUDIO_GRC3_H
#define AUDIO_GRC3_H

#define GRC3_MAXHISTORY 4096

#ifdef __cplusplus
extern "C"
{
#endif

typedef struct grc3state {
    uint32_t srcrate;
    uint32_t dstrate;
    uint32_t ptr;
    uint32_t ptr_incv;

    uint32_t sat;
    uint32_t filtfactor;
    int32_t *historyptr;
    int32_t dummy_pad1;

    int32_t history[GRC3_MAXHISTORY * 2];

    uint32_t outsz;
} grc3state_t;


/* BEGIN CSTYLED */
/*****************************************************************************

    Tutorial on how to use GRC3 rate conversion

1.  First, you create an instance of grc3state_t for each channel. If you
    are working with stereo files - you will need 2 of such instances,
    for quadro - 4.

    The instances may be allocated in either static or dynamic memory - that
    makes no difference to the convertor. So, if your program has to process
    one stereo stream, there's no reason why should you use malloc/free to
    allocate/deallocate structures. Also, in device drivers, you can
    use static variables as well:

    static grc3state_t grc[2]; // for two channels


2.  Before starting any conversion, grc3state_t instances should be initialized
    properly, and you do this with grc3_setup function. Function itself does
    not allocate additional memory or change anything except grc3state_t
    structure, so this is thread safe, and you don't have to do additional
    "deinitialization".

    If you are doing interleaved audio (stereo/quadro/whatever) conversion,
    you should do setup on each of the channels, and should have separate
    instance of grc3state_t for each channel. As you will understand further,
    such conversion is done separately. And now, the setup function:

    int grc3_setup( grc3state_t *grc,
            uint32_t    fromRate,
        uint32_t    toRate );

    grc   - pointer to grc3state_t instance
    fromRate  - source sample rate
    toRate    - destination sample rate

    Note, that sample rates itself are not important - the important thing
    is ratio between those sample rates. So, for example, if you have to
    convert from 24000Hz to 48000Hz, it's ok to write:

    grc3_setup( &grc[0], 240, 480 );

    Sometimes (in MIDI synths) it would be desired to use fractional sample
    rates. For example, setup for conversion from 33100.78 to 48000 may look
    like this:

    grc3_setup( &grc[0], 3310078, 4800000);

    Note, that on stereo, GRC3 setup will look like this:

    static grc3state_t grc[2];

    // ...

    grc3_setup( &grc[0], 3310078, 4800000)
        grc3_setup( &grc[1], 3310078, 4800000);


    Note, that you should not rely on grc3_setup's fast execution or any
    execution timing. It may contain some massive arithmetic and even huge
    loops, so avoid putting grc3_setup to inner loops and calling in
    latency-dependent code.


3.  Next, before running a stream through grc3_convert function, you should
    reset each of grc3state_t instance used:

    void grc3_reset(grc3state_t *grc);


    grc - pointer to GRC3 instance variable

    So, for stereo, this appears to be:

    static grc3state_t grc[2];

    // ...

    grc3_reset( &grc[0] );
    grc3_reset( &grc[1] );


4.  Finally, doing conversion is easy:

    void grc3_convert( grc3state_t *grc,
              int          domain,
          int      quality,
              const void  *src,
          void    *dst,
          int          maxInSize,
          int      maxOutSize,
          int      interleave,
          int      offset );


    grc    - pointer to initialized grc3state_t instance; you
             can specify NULL to check whether a particular
         domain/quality pair is supported, check return value

    quality    - quality to use for conversion, supported values are:

             0 - D lowest quality (normally equals to low quality)
         1 - L  low quality    (spline interpolation)
         2 - M  medium quality (lagrange interpolation)
         3 - H  high quality
         4 - HX high quality   (high quality with extra precision)
         5 - P  production quality

         6 - PX production quality (prod quality with extra precision)
             (PX is currently disabled because it causes a crash)

    src    - source audio buffer

    dst    - destination audio buffer;

    maxInSize  - size of input buffer (in samples per channel!)

    maxOutSize - size of output buffer (in samples per channel!)
             (will never overrun this size)

    interleave - interleave factor; for MONO or non-interleaved data
             it should be equal to 1;

         2 - STEREO interleaved audio
         4 - QUADRO interleaved audio

         So, basically, this parameter should be equal to number
         of interleaved channels

    offset     - number of interleaved channel currently processing,
             starting from 0; for MONO or non-interleaved data
         it should be equal to 0


         For unsupported quality values, it will fall back to
         "D" quality (the lowest one)

             also on return it sets:

         grc->outsz  == number of output samples

         Note, that if quality is not supported,
         calling the function with real data will fall back
         to the worst quality available.

         Note that this version of GRC3 only supports 24-bit
         native endian.  (Modified by Sun for performance.)


5.  Interleaved processing of N channels is done like this:


    static grc3state_t grc[N];
    int t;

    //...


    for(t=0; t<N; t++)
    {
    grc3_setup( &grc[t], 22050, 48000 );

    grc3_reset( &grc[t] );
    }


    //...

    while (...) {

    for(t = 0; t < N; t++) {
        grc3_convert(&grc[t],   // instance pointer
              4,            // quality
              in_buffer,    // input buffer
          out_buffer,       // input buffer
          in_samples_count, // number of samples
                    // in in_buffer
          2048,             // size of out_buffer
          N, t              // num of channels, channel#
        );
    }


    // Normally, for interleaved data, ->outsz of all instances will
    // be the same for the same stream

    put_sound_somewhere(out_buffer,
             grc[0]->outsz * N * sizeof(out_buffer[0]) );
    }


6.  If you use the same storage and the same setup for processing few separate
    non-related sounds, to prevent the feedback of sound1's tail to sound2's
    beginning - do grc3_reset on the state instances before calling
    grc_convert.

*****************************************************************************
*/
/* END CSTYLED */

void grc3_setup(grc3state_t *, uint32_t fromRate, uint32_t toRate);

void grc3_reset(grc3state_t *);

void grc3_convert(grc3state_t *, int quality,
    const void *src, void *dst, int sz, int bufsz, int inc, int offset);

#ifdef __cplusplus
};
#endif

#endif  /* AUDIO_GRC3_H */