1 /*

     2 * Copyright (c) 2010 Ixonos Plc.

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

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

     6 * which accompanies this distribution, and is available

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

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - Initial contribution

    11 *

    12 * Contributors:

    13 * Ixonos Plc

    14 *

    15 * Description:

    16 *

    17 */

    18 

    19 

    20 /**************************************************************************

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

    22 

    23   Author(s): Juha Ojanpera

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

    25   *************************************************************************/

    26 

    27 /*-- project headers --*/

    28 #include "mpaud.h"

    29 #include "mpheader.h"

    30 #include "mp3tool.h"

    31 

    32 /**************************************************************************

    33   Internal Objects

    34   *************************************************************************/

    35 

    36 /**************************************************************************

    37   Title        : L3BitReservoir

    38 

    39   Purpose      : Layer III bit reservoir subroutine.

    40 

    41   Usage        : y = L3BitReservoir(mp)

    42 

    43   Input        : mp - mp3 stream parameters

    44 

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

    46                      Value -1 indicates that an error has occured during

    47                      decoding (invalid bitstream syntax found)

    48 

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

    50                  sense that decoding of current frame should not be continued.

    51                  Instead, the decoder should be re-initialized.

    52 

    53   Author(s)    : Juha Ojanpera

    54   *************************************************************************/

    55 

    56 INLINE int16

    57 L3BitReservoir(CMPAudDec *mp)

    58 {

    59   int16 bytes_to_discard;

    60   int16 flush_main;

    61   int32 bits_read;

    62   TBitStream *br;

    63 

    64   br = &mp->br;

    65 

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

    67 

    68   if(mp->WasSeeking == FALSE)

    69   {

    70     /*-- Byte alignment. --*/

    71     bits_read = BsGetBitsRead(br);

    72     flush_main = (int16) (bits_read & 7);

    73     if(flush_main)

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

    75 

    76     /*

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

    78      */

    79     if(mp->SkipBr == FALSE)

    80     {

    81       BsClearBitsRead(br);

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

    83     }

    84 

    85     /*

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

    87      * frame to find the start of next frame.

    88      */

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

    90     

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

    92     BsClearBitsRead(br);

    93     

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

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

    96     

    97     if(bytes_to_discard < 0)

    98     {

    99       BsClearBitsRead(br);

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

   101       mp->SkipBr = TRUE;

   102       return (-1);

   103     }

   104 

   105     mp->SkipBr = FALSE;

   106 

   107     if(bytes_to_discard)

   108     {

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

   110       BsSkipNBits(br, bytes_to_discard << 3);

   111     }

   112   }

   113   else

   114   {

   115     bytes_to_discard = 0;

   116 

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

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

   119 

   120     mp->SkipBr = FALSE;

   121     mp->WasSeeking = FALSE;

   122     

   123     if(mp->side_info->main_data_begin)

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

   125 

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

   127     BsClearBitsRead(br);

   128   }

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

   130 

   131   return (bytes_to_discard);

   132 }

   133 

   134 /**************************************************************************

   135   Title        : DeleteMPAudDec

   136 

   137   Purpose      : Releases resources allocated to the mp3 decoder core.

   138 

   139   Usage        : y = DeleteMPAudDec(mpAud)

   140 

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

   142 

   143   Output       : y     - NULL

   144 

   145   Author(s)    : Juha Ojanpera

   146   *************************************************************************/

   147 

   148 

   149 INLINE uint8

   150 GetLayer3Version(TMpTransportHandle *tHandle)

   151 {

   152   uint8 mp_version;

   153   

   154   /*

   155    * Which version of mp3 ?

   156    */

   157   if(version(&tHandle->header))

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

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

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

   161   else

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

   163 

   164   return (mp_version);

   165 }