/*****************************************************************************

 * faad.c: AAC decoder using libfaad2

 *****************************************************************************

 * Copyright (C) 2001, 2003 VLC authors and VideoLAN

 *

 * Authors: Laurent Aimar <fenrir@via.ecp.fr>

 *          Gildas Bazin <gbazin@videolan.org>

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation; either version 2.1 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

 * GNU Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.

 *****************************************************************************/

/*****************************************************************************

 * NOTA BENE: this module requires the linking against a library which is

 * known to require licensing under the GNU General Public License version 2

 * (or later). Therefore, the result of compiling this module will normally

 * be subject to the terms of that later license.

 *****************************************************************************/

#ifdef HAVE_CONFIG_H

# include "config.h"

#endif

#include <assert.h>

#include <stdbit.h>

#include <vlc_common.h>

#include <vlc_plugin.h>

#include <vlc_input_item.h>

#include <vlc_codec.h>

#include <vlc_cpu.h>

#include <vlc_aout.h>

#include <faad.h>

#if !defined(FAAD2_VERSION) // FAAD2_VERSION added in 2.10.1

# define PATCH_PCA

#endif

#include <neaacdec.h>

#include "../packetizer/mpeg4audio.h"

/*****************************************************************************

 * Module descriptor

 *****************************************************************************/

static int  Open( vlc_object_t * );

static void Close( vlc_object_t * );

vlc_module_begin ()

    set_description( N_("AAC audio decoder (using libfaad2)") )

    set_capability( "audio decoder", 100 )

    set_subcategory( SUBCAT_INPUT_ACODEC )

    set_callbacks( Open, Close )

vlc_module_end ()

/****************************************************************************

 * Local prototypes

 ****************************************************************************/

static int DecodeBlock( decoder_t *, block_t * );

static void Flush( decoder_t * );

static void DoReordering( uint32_t *, uint32_t *, int, int, uint8_t * );

typedef struct

{

    /* faad handler */

    NeAACDecHandle *hfaad;

    /* samples */

    date_t date;

    vlc_tick_t i_last_length;

    /* temporary buffer */

    block_t *p_block;

    /* Channel positions of the current stream (for re-ordering) */

    uint32_t pi_channel_positions[MPEG4_ASC_MAX_INDEXEDPOS];

    bool b_sbr, b_ps, b_discontinuity;

} decoder_sys_t;

static_assert (MPEG4_ASC_MAX_INDEXEDPOS == LFE_CHANNEL, "Mismatch");

#define FAAD_CHANNEL_ID_COUNT (LFE_CHANNEL + 1)

static const uint32_t pi_tovlcmapping[FAAD_CHANNEL_ID_COUNT] =

{

    [UNKNOWN_CHANNEL]      = 0,

    [FRONT_CHANNEL_CENTER] = AOUT_CHAN_CENTER,

    [FRONT_CHANNEL_LEFT]   = AOUT_CHAN_LEFT,

    [FRONT_CHANNEL_RIGHT]  = AOUT_CHAN_RIGHT,

    [SIDE_CHANNEL_LEFT]    = AOUT_CHAN_MIDDLELEFT,

    [SIDE_CHANNEL_RIGHT]   = AOUT_CHAN_MIDDLERIGHT,

    [BACK_CHANNEL_LEFT]    = AOUT_CHAN_REARLEFT,

    [BACK_CHANNEL_RIGHT]   = AOUT_CHAN_REARRIGHT,

    [BACK_CHANNEL_CENTER]  = AOUT_CHAN_REARCENTER,

    [LFE_CHANNEL]          = AOUT_CHAN_LFE

};

/*****************************************************************************

 * OpenDecoder: probe the decoder and return score

 *****************************************************************************/

static int Open( vlc_object_t *p_this )

{

    decoder_t *p_dec = (decoder_t*)p_this;

    decoder_sys_t *p_sys;

    NeAACDecConfiguration *cfg;

    if( p_dec->fmt_in->i_codec != VLC_CODEC_MP4A ||

        p_dec->fmt_in->i_profile >= AAC_PROFILE_ELD ||

        (p_dec->fmt_in->i_extra > 1 &&

         (GetWBE(p_dec->fmt_in->p_extra) & 0xffe0) >= 0xf8e0)) /* ELD AOT */

    {

        return VLC_EGENERIC;

    }

    /* Allocate the memory needed to store the decoder's structure */

    if( ( p_dec->p_sys = p_sys = malloc( sizeof(*p_sys) ) ) == NULL )

        return VLC_ENOMEM;

    /* Open a faad context */

    if( ( p_sys->hfaad = NeAACDecOpen() ) == NULL )

    {

        msg_Err( p_dec, "cannot initialize faad" );

        free( p_sys );

        return VLC_EGENERIC;

    }

    char * vinfo[2];

    if( NeAACDecGetVersion( &vinfo[0], &vinfo[1] ) == 0 )

        msg_Dbg( p_dec, "using version " FAAD2_VERSION " - %s", vinfo[0] );

    /* Misc init */

    p_dec->fmt_out.audio.channel_type = p_dec->fmt_in->audio.channel_type;

    if( p_dec->fmt_in->i_extra > 0 )

    {

        /* We have a decoder config so init the handle */

        unsigned long i_rate;

        unsigned char i_channels;

        if( NeAACDecInit2( p_sys->hfaad, p_dec->fmt_in->p_extra,

                           p_dec->fmt_in->i_extra,

                           &i_rate, &i_channels ) < 0 ||

                i_channels >= MPEG4_ASC_MAX_INDEXEDPOS )

        {

            msg_Err( p_dec, "Failed to initialize faad using extra data" );

            NeAACDecClose( p_sys->hfaad );

            free( p_sys );

            return VLC_EGENERIC;

        }

        p_dec->fmt_out.audio.i_rate = i_rate;

        p_dec->fmt_out.audio.i_channels = i_channels;

        p_dec->fmt_out.audio.i_physical_channels

            = MPEG4_asc_channelsbyindex[i_channels];

        date_Init( &p_sys->date, i_rate, 1 );

    }

    else

    {

        p_dec->fmt_out.audio.i_physical_channels = 0;

        /* Will be initialised from first frame */

        p_dec->fmt_out.audio.i_rate = 0;

        p_dec->fmt_out.audio.i_channels = 0;

        date_Set( &p_sys->date, VLC_TICK_INVALID );

    }

    p_dec->fmt_out.i_codec = HAVE_FPU ? VLC_CODEC_FL32 : VLC_CODEC_S16N;

    p_dec->fmt_out.audio.i_chan_mode = p_dec->fmt_in->audio.i_chan_mode;

    /* Set the faad config */

    cfg = NeAACDecGetCurrentConfiguration( p_sys->hfaad );

    if( p_dec->fmt_in->audio.i_rate )

        cfg->defSampleRate = p_dec->fmt_in->audio.i_rate;

    cfg->outputFormat = HAVE_FPU ? FAAD_FMT_FLOAT : FAAD_FMT_16BIT;

    if( !NeAACDecSetConfiguration( p_sys->hfaad, cfg ) )

    {

        msg_Err( p_dec, "Failed to set faad configuration" );

        NeAACDecClose( p_sys->hfaad );

        free( p_sys );

        return VLC_EGENERIC;

    }

    p_sys->i_last_length = 0;

    /* buffer */

    p_sys->p_block = NULL;

    p_sys->b_discontinuity =

    p_sys->b_sbr = p_sys->b_ps = false;

    p_dec->pf_decode = DecodeBlock;

    p_dec->pf_flush  = Flush;

    return VLC_SUCCESS;

}

/*****************************************************************************

 * FlushBuffer:

 *****************************************************************************/

static void FlushBuffer( decoder_sys_t *p_sys, size_t i_used )

{

    block_t *p_block = p_sys->p_block;

    if( p_block )

    {

        if( i_used < p_block->i_buffer )

        {

            /* Drop padding */

            for( ; i_used < p_block->i_buffer; i_used++ )

                if( p_block->p_buffer[i_used] != 0x00 )

                    break;

            p_block->i_buffer -= i_used;

            p_block->p_buffer += i_used;

        }

        else p_block->i_buffer = 0;

        if( p_block->i_buffer == 0 )

        {

            block_Release( p_block );

            p_sys->p_block = NULL;

        }

    }

}

/*****************************************************************************

 * Flush:

 *****************************************************************************/

static void Flush( decoder_t *p_dec )

{

    decoder_sys_t *p_sys = p_dec->p_sys;

    date_Set( &p_sys->date, VLC_TICK_INVALID );

    FlushBuffer( p_sys, SIZE_MAX );

}

/*****************************************************************************

 * DecodeBlock:

 *****************************************************************************/

static int DecodeBlock( decoder_t *p_dec, block_t *p_block )

{

    decoder_sys_t *p_sys = p_dec->p_sys;

    if( !p_block ) /* No Drain */

        return VLCDEC_SUCCESS;

    if( p_block->i_flags & (BLOCK_FLAG_DISCONTINUITY | BLOCK_FLAG_CORRUPTED) )

    {

        Flush( p_dec );

        if( p_block->i_flags & (BLOCK_FLAG_CORRUPTED) )

        {

            block_Release( p_block );

            return VLCDEC_SUCCESS;

        }

    }

    /* Remove ADTS header if we have decoder specific config */

    if( p_dec->fmt_in->i_extra && p_block->i_buffer > 7 )

    {

        if( p_block->p_buffer[0] == 0xff &&

            ( p_block->p_buffer[1] & 0xf0 ) == 0xf0 ) /* syncword */

        {   /* ADTS header present */

            size_t i_header_size; /* 7 bytes (+ 2 bytes for crc) */

            i_header_size = 7 + ( ( p_block->p_buffer[1] & 0x01 ) ? 0 : 2 );

            /* FIXME: multiple blocks per frame */

            if( p_block->i_buffer > i_header_size )

            {

                p_block->p_buffer += i_header_size;

                p_block->i_buffer -= i_header_size;

            }

        }

    }

    const vlc_tick_t i_pts = p_block->i_pts;

    /* Append block as temporary buffer */

    if( p_sys->p_block == NULL )

    {

        p_sys->p_block = p_block;

    }

    else

    {

        p_sys->p_block->p_next = p_block;

        block_t *p_prev = p_sys->p_block;

        p_sys->p_block = block_ChainGather( p_sys->p_block );

        if( p_sys->p_block == NULL )

            block_ChainRelease( p_prev );

    }

    /* !Warn: do not use p_block beyond this point */

    if( p_dec->fmt_out.audio.i_rate == 0 )

    {

        unsigned long i_rate = 0;

        unsigned char i_channels;

        /* Init from DecoderConfig */

        if( p_dec->fmt_in->i_extra > 0 &&

            NeAACDecInit2( p_sys->hfaad, p_dec->fmt_in->p_extra,

                           p_dec->fmt_in->i_extra, &i_rate, &i_channels ) != 0 )

        {

            /* Failed, will try from data */

            i_rate = 0;

        }

        if( i_rate == 0 && p_sys->p_block && p_sys->p_block->i_buffer )

        {

            /* Init faad with the first frame */

            long i_read = NeAACDecInit( p_sys->hfaad,

                                        p_sys->p_block->p_buffer, p_sys->p_block->i_buffer,

                                        &i_rate, &i_channels );

            if( i_read < 0 || (size_t) i_read > p_sys->p_block->i_buffer )

                i_rate = 0;

            else

                FlushBuffer( p_sys, i_read );

        }

        if( i_rate == 0 )

        {

            /* Can not init decoder at all for now */

            FlushBuffer( p_sys, SIZE_MAX );

            return VLCDEC_SUCCESS;

        }

        /* Decoder Initialized */

        p_dec->fmt_out.audio.i_rate = i_rate;

        p_dec->fmt_out.audio.i_channels = i_channels;

        p_dec->fmt_out.audio.i_physical_channels

            = MPEG4_asc_channelsbyindex[i_channels];

        date_Init( &p_sys->date, i_rate, 1 );

    }

    if( i_pts != VLC_TICK_INVALID && i_pts != date_Get( &p_sys->date ) )

    {

        if( p_sys->i_last_length == 0 ||

            /* We need to be permissive and rebase dts when it's really way off */

            llabs( i_pts - date_Get( &p_sys->date ) ) > p_sys->i_last_length * 3 / 2  )

            date_Set( &p_sys->date, i_pts );

    }

    else if( date_Get( &p_sys->date ) == VLC_TICK_INVALID )

    {

        /* We've just started the stream, wait for the first PTS. */

        FlushBuffer( p_sys, SIZE_MAX );

        return VLCDEC_SUCCESS;

    }

    /* Decode all data */

    while( p_sys->p_block && p_sys->p_block->i_buffer > 0 )

    {

        void *samples;

        NeAACDecFrameInfo frame;

        block_t *p_out = NULL;

        samples = NeAACDecDecode( p_sys->hfaad, &frame,

                                  p_sys->p_block->p_buffer,

                                  p_sys->p_block->i_buffer );

        if( frame.error > 0 )

        {

            msg_Warn( p_dec, "%s", NeAACDecGetErrorMessage( frame.error ) );

            if( frame.error == 21 || frame.error == 12 )

            {

                /*

                 * Once an "Unexpected channel configuration change"

                 * or a "Invalid number of channels" error

                 * occurs, it will occurs afterwards, and we got no sound.

                 * Reinitialization of the decoder is required.

                 */

                unsigned long i_rate;

                unsigned char i_channels;

                NeAACDecHandle *hfaad;

                NeAACDecConfiguration *cfg,*oldcfg;

                oldcfg = NeAACDecGetCurrentConfiguration( p_sys->hfaad );

                hfaad = NeAACDecOpen();

                cfg = NeAACDecGetCurrentConfiguration( hfaad );

                if( oldcfg->defSampleRate )

                    cfg->defSampleRate = oldcfg->defSampleRate;

                cfg->defObjectType = oldcfg->defObjectType;

                cfg->outputFormat = oldcfg->outputFormat;

                NeAACDecSetConfiguration( hfaad, cfg );

                if( NeAACDecInit( hfaad,

                                  p_sys->p_block->p_buffer,

                                  p_sys->p_block->i_buffer,

                                  &i_rate,&i_channels ) < 0 )

                {

                    /* reinitialization failed */

                    NeAACDecClose( hfaad );

                    NeAACDecSetConfiguration( p_sys->hfaad, oldcfg );

                }

                else

                {

                    NeAACDecClose( p_sys->hfaad );

                    p_sys->hfaad = hfaad;

                    p_dec->fmt_out.audio.i_rate = i_rate;

                    p_dec->fmt_out.audio.i_channels = i_channels;

                    p_dec->fmt_out.audio.i_physical_channels

                        = MPEG4_asc_channelsbyindex[i_channels];

                    date_Init( &p_sys->date, i_rate, 1 );

                }

            }

            Flush( p_dec );

            p_sys->b_discontinuity = true;

            continue;

        }

        if( frame.channels == 0 || frame.channels >= 64 )

        {

            msg_Warn( p_dec, "invalid channels count: %i", frame.channels );

            if( frame.channels == 0 )

                p_sys->b_discontinuity = true;

            FlushBuffer( p_sys, frame.bytesconsumed ? frame.bytesconsumed : SIZE_MAX );

            continue;

        }

        if( frame.samples == 0 )

        {

            msg_Warn( p_dec, "decoded zero sample" );

            FlushBuffer( p_sys, frame.bytesconsumed ? frame.bytesconsumed : SIZE_MAX );

            continue;

        }

        /* We decoded a valid frame */

        if( p_dec->fmt_out.audio.i_rate != frame.samplerate )

        {

            date_Init( &p_sys->date, frame.samplerate, 1 );

            date_Set( &p_sys->date, i_pts );

        }

        p_dec->fmt_out.audio.i_rate = frame.samplerate;

        /* Adjust stream info when dealing with SBR/PS */

        bool b_sbr = (frame.sbr == 1) || (frame.sbr == 2);

        if( p_sys->b_sbr != b_sbr || p_sys->b_ps != frame.ps )

        {

            const char *psz_ext = (b_sbr && frame.ps) ? "SBR+PS" :

                                    b_sbr ? "SBR" : "PS";

            msg_Dbg( p_dec, "AAC %s (channels: %u, samplerate: %lu)",

                    psz_ext, frame.channels, frame.samplerate );

            if( !p_dec->p_description )

                p_dec->p_description = vlc_meta_New();

            if( p_dec->p_description )

                vlc_meta_SetExtra( p_dec->p_description, _("AAC extension"), psz_ext );

            p_sys->b_sbr = b_sbr;

            p_sys->b_ps = frame.ps;

        }

#ifdef PATCH_PCA

        /* PS Enabled FAAD PCA bug hotfix (contribs has patch) */

        if( frame.channels == 8 )

        {

            const uint8_t psbugconfig[3][8] = { { 2, 3, 2, 3, 2, 3, 6, 7 },  /* fdk 7.1 (4 Front) */

                                                { 2, 3, 2, 3, 2, 3, 4, 5 },  /* 7.1 */

                                                { 1, 2, 3, 4, 5, 6, 7, 9 } };/* fixed */

            for( size_t i=0; i<2; i++ )

            {

                if( !memcmp( frame.channel_position, psbugconfig[i], 8 ) )

                {

                    msg_Warn( p_dec, "Unpatched FAAD2 library with PS Bug. Trying to workaround !" );

                    memcpy( frame.channel_position, psbugconfig[2], 8 );

                    break;

                }

            }

        }

        /* Hotfix channels misdetection/repetition for FDK 7.1 */

        struct

        {

            const uint8_t chans;

            const uint8_t faulty[8];

            const uint8_t fixed[8];

        } const channel_repeat_fixes[] = {

            { 7, { 2, 3, 2, 3, 2, 3, 6 },    { 1, 2, 3, 6, 7, 8, 9 }    }, /* 3F 3R LFE #18273 */

            { 8, { 1, 2, 3, 6, 7, 6, 7, 9 }, { 1, 2, 3, 6, 7, 4, 5, 9 } }, /* FDK encoded 7.1 */

        };

        for( size_t i=0; i<ARRAY_SIZE(channel_repeat_fixes); i++ )

        {

            if( channel_repeat_fixes[i].chans == frame.channels &&

                !memcmp( frame.channel_position, channel_repeat_fixes[i].faulty,

                                                 channel_repeat_fixes[i].chans ) )

            {

                msg_Warn( p_dec, "Patching for Front channel repeat bug" );

                memcpy( frame.channel_position, channel_repeat_fixes[i].fixed,

                                                channel_repeat_fixes[i].chans );

                break;

            }

        }

#endif

        /* Handle > 1 local pair 5.1 setups.

           In case of more than 1 channel pair per area, faad will have repeats

           in channels sequence. We need to remap to available surround channels.

           Front > Middle > Rear:

           In case of 4 middle, it maps to 2F 2M if no previous front.

           In case of 4 rear, it maps to 2M 2R if no previous rear.

        */

        unsigned i_faadused = 0;

        for( unsigned i=0; i<frame.channels; i++ )

            if( frame.channel_position[i] > 0 )

                i_faadused |= 1 << frame.channel_position[i];

        for( size_t i=3; i<frame.channels; i++ )

        {

             if( frame.channel_position[i - 3] == frame.channel_position[i - 1] &&

                 frame.channel_position[i - 2] == frame.channel_position[i] &&

                 frame.channel_position[i - 1] >= SIDE_CHANNEL_LEFT &&

                 frame.channel_position[i - 1] <= BACK_CHANNEL_CENTER &&

                 frame.channel_position[i - 1] >= SIDE_CHANNEL_LEFT &&

                 frame.channel_position[i - 1] <= BACK_CHANNEL_CENTER )

             {

                if( ( (1 << (frame.channel_position[i - 3] - 2)) & i_faadused ) == 0 &&

                    ( (1 << (frame.channel_position[i - 2] - 2)) & i_faadused ) == 0 )

                {

                    frame.channel_position[i - 3] -= 2;

                    frame.channel_position[i - 2] -= 2;

                    i_faadused |= 1 << frame.channel_position[i - 3];

                    i_faadused |= 1 << frame.channel_position[i - 2];

                }

             }

        }

        /* Convert frame.channel_position to our own channel values */

        p_dec->fmt_out.audio.i_physical_channels = 0;

        uint8_t  pi_neworder_table[64] = {0};

        uint32_t pi_faad_channels_positions[64 + 1] = {0};

        bool b_reorder = false;

        if (p_dec->fmt_out.audio.channel_type == AUDIO_CHANNEL_TYPE_BITMAP)

        {

            for( size_t i = 0; i < frame.channels; i++ )

            {

                unsigned pos = frame.channel_position[i];

                if( likely(pos < FAAD_CHANNEL_ID_COUNT) )

                {

                    pi_faad_channels_positions[i] = pi_tovlcmapping[pos];

                    p_dec->fmt_out.audio.i_physical_channels |= pi_faad_channels_positions[i];

                }

                else pi_faad_channels_positions[i] = 0;

            }

        }

        else if (p_dec->fmt_out.audio.channel_type == AUDIO_CHANNEL_TYPE_AMBISONICS

            && frame.channels == 4)

        {

            pi_faad_channels_positions[0] = AOUT_CHAN_REARCENTER;

            pi_faad_channels_positions[1] = AOUT_CHAN_LEFT;

            pi_faad_channels_positions[2] = AOUT_CHAN_RIGHT;

            pi_faad_channels_positions[3] = AOUT_CHAN_CENTER;

            p_dec->fmt_out.audio.i_physical_channels =

                AOUT_CHAN_CENTER | AOUT_CHAN_LEFT

                | AOUT_CHAN_RIGHT | AOUT_CHAN_REARCENTER;

        }

        b_reorder = aout_CheckChannelReorder( pi_faad_channels_positions, NULL,

            p_dec->fmt_out.audio.i_physical_channels, pi_neworder_table );

        p_dec->fmt_out.audio.i_channels = stdc_count_ones(p_dec->fmt_out.audio.i_physical_channels);

        if( !decoder_UpdateAudioFormat( p_dec ) && p_dec->fmt_out.audio.i_channels > 0 )

            p_out = decoder_NewAudioBuffer( p_dec, frame.samples / p_dec->fmt_out.audio.i_channels );

        if( p_out )

        {

            p_out->i_pts = date_Get( &p_sys->date );

            p_out->i_length = date_Increment( &p_sys->date,

                                              frame.samples / frame.channels )

                              - p_out->i_pts;

            p_sys->i_last_length = p_out->i_length;

            if ( p_dec->fmt_out.audio.channel_type == AUDIO_CHANNEL_TYPE_BITMAP )

            {

                /* Don't kill speakers if some weird mapping does not gets 1:1 */

                if( stdc_count_ones(p_dec->fmt_out.audio.i_physical_channels) != frame.channels )

                    memset( p_out->p_buffer, 0, p_out->i_buffer );

            }

            /* FIXME: replace when aout_channel_reorder can take samples from a different buffer */

            if( b_reorder )

                DoReordering( (uint32_t *)p_out->p_buffer, samples,

                              frame.samples / frame.channels, frame.channels,

                              pi_neworder_table );

            else

                 memcpy( p_out->p_buffer, samples, p_out->i_buffer );

            if( p_sys->b_discontinuity )

            {

                p_out->i_flags |= BLOCK_FLAG_DISCONTINUITY;

                p_sys->b_discontinuity = false;

            }

            decoder_QueueAudio( p_dec, p_out );

        }

        else

        {

            date_Increment( &p_sys->date, frame.samples / frame.channels );

        }

        FlushBuffer( p_sys, frame.bytesconsumed ? frame.bytesconsumed : SIZE_MAX );

        if( p_sys->p_block && p_sys->p_block->i_buffer == 1 )

        {

            /* Drop byte of padding */

            FlushBuffer( p_sys, 0 );

        }

    }

    return VLCDEC_SUCCESS;

}

/*****************************************************************************

 * Close:

 *****************************************************************************/

static void Close( vlc_object_t *p_this )

{

    decoder_t *p_dec = (decoder_t *)p_this;

    decoder_sys_t *p_sys = p_dec->p_sys;

    NeAACDecClose( p_sys->hfaad );

    FlushBuffer( p_sys, SIZE_MAX );

    free( p_sys );

}

/*****************************************************************************

 * DoReordering: do some channel re-ordering (the ac3 channel order is

 *   different from the aac one).

 *****************************************************************************/

static void DoReordering( uint32_t *p_out, uint32_t *p_in, int i_samples,

                          int i_nb_channels, uint8_t *pi_chan_positions )

{

#if HAVE_FPU

    #define CAST_SAMPLE(a) a

#else

    #define CAST_SAMPLE(a) ((uint16_t *)a)

#endif

    /* Do the actual reordering */

    for( int i = 0; i < i_samples; i++ )

    {

        for( int j = 0; j < i_nb_channels; j++ )

        {

            CAST_SAMPLE(p_out)[i * i_nb_channels + pi_chan_positions[j]] =

                CAST_SAMPLE(p_in)[i * i_nb_channels + j];

        }

    }

}