/*

* Copyright (c) 2010 Ixonos Plc.

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - Initial contribution

*

* Contributors:

* Ixonos Plc

*

* Description:

*

*/

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

  mpaud.cpp - MPEG-1, MPEG-2 LSF and MPEG-2.5 layer III bitstream decoder.

  Author(s): Juha Ojanpera

  Copyright (c) 1999-2004 by Nokia Research Center, Speech and Audio Systems.

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

/*-- project headers --*/

#include "mpaud.h"

#include "mpheader.h"

#include "mp3tool.h"

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

  Internal Objects

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

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

  Title        : L3BitReservoir

  Purpose      : Layer III bit reservoir subroutine.

  Usage        : y = L3BitReservoir(mp)

  Input        : mp - mp3 stream parameters

  Output       : y - # of bytes discarded from the bit reservoir buffer.

                     Value -1 indicates that an error has occured during

                     decoding (invalid bitstream syntax found)

  Explanation  : Return value -1 should be regarded as a fatal error in the

                 sense that decoding of current frame should not be continued.

                 Instead, the decoder should be re-initialized.

  Author(s)    : Juha Ojanpera

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

INLINE int16

L3BitReservoir(CMPAudDec *mp)

{

  int16 bytes_to_discard;

  int16 flush_main;

  int32 bits_read;

  TBitStream *br;

  br = &mp->br;

  /*------------ Start of bit reservoir processing. ------------------*/

  if(mp->WasSeeking == FALSE)

  {

    /*-- Byte alignment. --*/

    bits_read = BsGetBitsRead(br);

    flush_main = (int16) (bits_read & 7);

    if(flush_main)

      BsSkipBits(br, (int16) (8 - flush_main));

    /*

     * Determine how many bits were left from the previous frame.

     */

    if(mp->SkipBr == FALSE)

    {

      BsClearBitsRead(br);

      BsSetBitsRead(br, (mp->PrevSlots << 3) - bits_read);

    }

    /*

     * Determine how many bytes need to be discarded from the previous

     * frame to find the start of next frame.

     */

    bytes_to_discard = (int16) ((BsGetBitsRead(br) >> 3) - mp->side_info->main_data_begin);

    /*-- Reset the bit reservoir bit counter. --*/

    BsClearBitsRead(br);

    /*-- # of slots available for this frame. --*/

    mp->PrevSlots = (int16) (mp->mpFileFormat->mainDataSlots + mp->side_info->main_data_begin);

    if(bytes_to_discard < 0)

    {

      BsClearBitsRead(br);

      BsSetBitsRead(br, mp->mpFileFormat->mainDataSlots << 3);

      mp->SkipBr = TRUE;

      return (-1);

    }

    mp->SkipBr = FALSE;

    if(bytes_to_discard)

    {

      mp->PrevSlots = (int16) (mp->PrevSlots + bytes_to_discard);

      BsSkipNBits(br, bytes_to_discard << 3);

    }

  }

  else

  {

    bytes_to_discard = 0;

    /*-- # of slots available for this frame. --*/

    mp->PrevSlots = (int16) (mp->mpFileFormat->mainDataSlots + mp->side_info->main_data_begin);

    mp->SkipBr = FALSE;

    mp->WasSeeking = FALSE;

    if(mp->side_info->main_data_begin)

      BsRewindNBits(br, mp->side_info->main_data_begin << 3);

    /*-- Reset the bit reservoir bit counter. --*/

    BsClearBitsRead(br);

  }

  /*-------------- End of bit reservoir processing. ------------------*/

  return (bytes_to_discard);

}

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

  Title        : DeleteMPAudDec

  Purpose      : Releases resources allocated to the mp3 decoder core.

  Usage        : y = DeleteMPAudDec(mpAud)

  Input        : mpAud - Layer I/II/III decoder core

  Output       : y     - NULL

  Author(s)    : Juha Ojanpera

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

INLINE uint8

GetLayer3Version(TMpTransportHandle *tHandle)

{

  uint8 mp_version;

  /*

   * Which version of mp3 ?

   */

  if(version(&tHandle->header))

    mp_version = 1; /*-- MPEG-1   --*/

  else if(!mp25version(&tHandle->header))

    mp_version = 2; /*-- MPEG-2   --*/

  else

    mp_version = 3; /*-- MPEG-2.5 --*/

  return (mp_version);

}