amrdecode.cpp

实现3GPP的GSM中AMR语音的CODECS。

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 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
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 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied.
 * See the License for the specific language governing permissions
 * and limitations under the License.
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 */
/****************************************************************************************
Portions of this file are derived from the following 3GPP standard:

    3GPP TS 26.073
    ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec
    Available from http://www.3gpp.org

(C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC)
Permission to distribute, modify and use this file under the standard license
terms listed above has been obtained from the copyright holder.
****************************************************************************************/
/*
------------------------------------------------------------------------------


 Pathname: ./audio/gsm-amr/c/src/amrdecode.c

     Date: 05/23/2001
------------------------------------------------------------------------------
 REVISION HISTORY

 Description:       AMRDecode now doesn't call getbits() or put_header_in().
                    It also now obtains a new bit_offset value from a constant
                    rather than from the returned value of getbits().

 Description:       AMRDecode now returns byte_offset rather than bit_offset,
                    so the program can access the next frame that is byte
                    aligned rather than packed without padding.

 Description:       The structure types Speech_Decode_FrameState are now
                    passed into amrdecode( ) using void pointers, so that
                    higher level functions don't need to know anything about
                    this structure type.

 Description: Changed input argument list. Added code to handle incoming DTX
              frames, and added call to wmf_to_ets function prior to calling
              GSMFrameDecode.

 Description: Made the following changes per comments from Phase 2/3 review:
              1. Changed all references to bit_offset to byte_offset.

 Description: Added input_type to the function interface and modified code
              to check type of conversion that needs to be made.

 Description: Modified pseudo-code to include IF2 and ETS input formats.
              Removed byte_offset from input list. Renamed speech_bits
              to speech_bits_ptr.

 Description: Added dec_input_format_tab.h in Include section. Modified
              pseudo-code to use correct table names. Renamed input_type to
              input_format and speech_bits to speech_bits_ptr.

 Description: Removed *prev_mode_ptr in the input argument list.

 Description: Made the following changes per comments from Phase 2/3 review:
              1. Removed dec_input_format_tab.h from Include section.
              2. Changed type definition of raw_pcm_buffer in the I/O
                 definition section.

 Description: Renamed WmfBytesPerFrame to WmfDecBytesPerFrame, and
              If2BytesPerFrame to If2DecBytesPerFrame.

 Description: Modified code so that the ETS testvectors could be fed directly
              to this function.

 Description: Changed '&' to '&&' in the setting of rx_type and mode for
              AMR_SID < frame_type < NO_DATA case.

 Description: Added code comments and made some code optimizations per Phase
              2/3 review comments.

 Description: Added conditional compile around the call to GSMFrameDecode to
              allow amrdecode.c to be used in the ETS reference console.

 Description:

------------------------------------------------------------------------------
*/

/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "amrdecode.h"
#include "cnst.h"
#include "typedef.h"
#include "frame.h"
#include "sp_dec.h"
#include "wmf_to_ets.h"
#include "if2_to_ets.h"
#include "frame_type_3gpp.h"

/*----------------------------------------------------------------------------
; MACROS
; Define module specific macros here
----------------------------------------------------------------------------*/


/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/


/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
; Function Prototype declaration
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL STORE/BUFFER/POINTER DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/

/*
------------------------------------------------------------------------------
 FUNCTION NAME: AMRDecode
------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    state_data      = pointer to a structure (type void)

    frame_type      = 3GPP frame type (enum Frame_Type_3GPP)

    speech_bits_ptr = pointer to the beginning of the raw encoded speech bits
                      for the current frame to be decoded (unsigned char)

    raw_pcm_buffer  = pointer to the output pcm outputs array (Word16)

    input_format    = input format used; valid values are AMR_WMF, AMR_IF2,
                      and AMR_ETS (Word16)

 Outputs:
    raw_pcm_buffer contains the newly decoded linear PCM speech samples
    state_data->prev_mode contains the new mode

 Returns:
    byte_offset     = address offset of the next frame to be processed or
                      error condition flag (-1) (int)

 Global Variables Used:
    WmfDecBytesPerFrame = table containing the number of core AMR data bytes
                          used by each codec mode for WMF input format (const
                          int)

    If2DecBytesPerFrame = table containing the number of core AMR data bytes
                          used by each codec mode for IF2 input format (const
                          int)

 Local Variables Needed:
    None

------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

 This function is the top level entry function to the GSM AMR Decoder library.

 First, it checks the input format type (input_format) to determine the type
 of de-formattting that needs to be done. If input_format is AMR_WMF, the input
 data is in WMF (aka, non-IF2) format and the function wmf_to_ets will be
 called to convert to the ETS format (1 bit/word, where 1 word = 16 bits),
 and byte_offset will be updated according to the contents of WmfDecBytesPerFrame
 table.

 If input_format is AMR_IF2, the input data is in IF2 format [1] and the
 function if2_to_ets will be called to convert to the ETS format, and
 byte_offset will be updated according to the contents of If2DecBytesPerFrame
 table.

 The codec mode and receive frame type is initialized based on the incoming
 frame_type.

 If input_format is AMR_ETS, the input data is in the ETS format. The receive
 frame type is set to the value in the first location of the buffer pointed to
 by speech_bits_ptr. Then, the encoded speech parameters in the buffer pointed
 to by speech_bits is copied to dec_ets_input_bfr and the type will be changed
 from unsigned char to Word16. Lastly, if the receive frame type is not
 RX_NO_DATA, the mode is obtained from the buffer pointed to by
 speech_bits_ptr, offset by MAX_SERIAL_SIZE+1, otherwise, the mode is set to
 the previous mode (found the in state_data->prev_mode).

 If input_format is an unsupported format, byte_offset will be set to -1, to
 indicate an error condition has occurred, and the function will exit.

 If there are no errors, GSMFrameDecode is called to decode a 20 ms frame. It
 puts the decoded linear PCM samples in the buffer pointed to by
 raw_pcm_buffer. Then, the prev_mode field of the structure pointed to by
 state_data is updated to the current mode.

 This function returns the new byte_offset value to indicate the address
 offset of the next speech frame to be decoded.

------------------------------------------------------------------------------
 REQUIREMENTS

 None

------------------------------------------------------------------------------
 REFERENCES

 [1] "AMR Speech Codec Frame Structure", 3GPP TS 26.101 version 4.1.0
     Release 4, June 2001

------------------------------------------------------------------------------
 PSEUDO-CODE

 Note: AMRSID_RXTYPE_BIT_OFFSET = 35
       AMRSID_RXMODE_BIT_OFFSET = 36
       NUM_AMRSID_RXMODE_BITS = 3


 // Set up Decoder state structure pointer
 Speech_Decode_FrameState *decoder_state
            = (Speech_Decode_FrameState *) state_data

 // Determine type of de-formatting

 // Decode WMF or IF2 frames
 IF ((input_format == AMR_RX_WMF) | (input_format == AMR_RX_IF2))
 THEN
     IF (input_format == AMR_RX_WMF)
     THEN
         // Convert incoming packetized raw WMF data to ETS format
         CALL wmf_to_ets(frame_type = frame_type
                         input_ptr = speech_bits_ptr
                         output_ptr = &dec_ets_input_bfr)
           MODIFYING(nothing)
           RETURNING(nothing)

         // Address offset of the start of next frame
         byte_offset = WmfDecBytesPerFrame[frame_type]

     ELSEIF (input_format == AMR_RX_IF2)
     THEN
         // Convert incoming packetized raw IF2 data to ETS format
         CALL if2_to_ets(frame_type = frame_type
                         input_ptr = speech_bits_ptr
                         output_ptr = &dec_ets_input_bfr)
           MODIFYING(nothing)
           RETURNING(nothing)

         // Address offset of the start of next frame
         byte_offset = If2DecBytesPerFrame[frame_type]

     ENDIF

       // Determine AMR codec mode and AMR RX frame type
     IF (frame_type <= AMR_122)
     THEN
         mode = (enum Mode) frame_type;
         rx_type = RX_SPEECH_GOOD;

     ELSEIF (frame_type == AMR_SID)
     THEN
         // Clear mode store prior to reading mode info from input buffer