| /* ------------------------------------------------------------------ |
| * Copyright (C) 1998-2009 PacketVideo |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * 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. |
| * ------------------------------------------------------------------- |
| */ |
| /* |
| ------------------------------------------------------------------------------ |
| |
| PacketVideo Corp. |
| MP3 Decoder Library |
| |
| Filename: pvmp3_seek_synch.cpp |
| |
| Functions: |
| pvmp3_seek_synch |
| pvmp3_header_sync |
| |
| |
| Date: 9/21/2007 |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| |
| Description: |
| |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| pvmp3_frame_synch |
| |
| Input |
| pExt = pointer to the external interface structure. See the file |
| pvmp3decoder_api.h for a description of each field. |
| Data type of pointer to a tPVMP3DecoderExternal |
| structure. |
| |
| pMem = void pointer to hide the internal implementation of the library |
| It is cast back to a tmp3dec_file structure. This structure |
| contains information that needs to persist between calls to |
| this function, or is too big to be placed on the stack, even |
| though the data is only needed during execution of this function |
| Data type void pointer, internally pointer to a tmp3dec_file |
| structure. |
| |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| search mp3 sync word, when found, it verifies, based on header parameters, |
| the locations of the very next sync word, |
| - if fails, then indicates a false sync, |
| - otherwise, it confirm synchronization of at least 2 consecutives frames |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| ------------------------------------------------------------------------------ |
| PSEUDO-CODE |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| |
| #include "pvmp3_seek_synch.h" |
| #include "pvmp3_getbits.h" |
| #include "s_tmp3dec_file.h" |
| #include "pv_mp3dec_fxd_op.h" |
| #include "pvmp3_tables.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 |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; EXTERNAL FUNCTION REFERENCES |
| ; Declare functions defined elsewhere and referenced in this module |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES |
| ; Declare variables used in this module but defined elsewhere |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; FUNCTION CODE |
| ----------------------------------------------------------------------------*/ |
| |
| |
| |
| ERROR_CODE pvmp3_frame_synch(tPVMP3DecoderExternal *pExt, |
| void *pMem) /* bit stream structure */ |
| { |
| uint16 val; |
| ERROR_CODE err; |
| |
| tmp3dec_file *pVars; |
| |
| pVars = (tmp3dec_file *)pMem; |
| |
| pVars->inputStream.pBuffer = pExt->pInputBuffer; |
| pVars->inputStream.usedBits = (pExt->inputBufferUsedLength << 3); // in bits |
| |
| |
| pVars->inputStream.inputBufferCurrentLength = (pExt->inputBufferCurrentLength); // in bits |
| |
| err = pvmp3_header_sync(&pVars->inputStream); |
| |
| if (err == NO_DECODING_ERROR) |
| { |
| /* validate synchronization by checking two consecutive sync words */ |
| |
| // to avoid multiple bitstream accesses |
| uint32 temp = getNbits(&pVars->inputStream, 21); |
| // put back whole header |
| pVars->inputStream.usedBits -= 21 + SYNC_WORD_LNGTH; |
| |
| int32 version; |
| |
| switch (temp >> 19) /* 2 */ |
| { |
| case 0: |
| version = MPEG_2_5; |
| break; |
| case 2: |
| version = MPEG_2; |
| break; |
| case 3: |
| version = MPEG_1; |
| break; |
| default: |
| version = INVALID_VERSION; |
| break; |
| } |
| |
| int32 freq_index = (temp << 20) >> 30; |
| |
| if (version != INVALID_VERSION && (freq_index != 3)) |
| { |
| int32 numBytes = fxp_mul32_Q28(mp3_bitrate[version][(temp<<16)>>28] << 20, |
| inv_sfreq[freq_index]); |
| |
| numBytes >>= (20 - version); |
| |
| if (version != MPEG_1) |
| { |
| numBytes >>= 1; |
| } |
| if ((temp << 22) >> 31) |
| { |
| numBytes++; |
| } |
| |
| if (numBytes > (int32)pVars->inputStream.inputBufferCurrentLength) |
| { |
| /* frame should account for padding and 2 bytes to check sync */ |
| pExt->CurrentFrameLength = numBytes + 3; |
| return (SYNCH_LOST_ERROR); |
| } |
| else if (numBytes == (int32)pVars->inputStream.inputBufferCurrentLength) |
| { |
| /* No enough data to validate, but current frame appears to be correct ( EOF case) */ |
| pExt->inputBufferUsedLength = pVars->inputStream.usedBits >> 3; |
| return (NO_DECODING_ERROR); |
| } |
| else |
| { |
| |
| int32 offset = pVars->inputStream.usedBits + ((numBytes) << 3); |
| |
| offset >>= INBUF_ARRAY_INDEX_SHIFT; |
| uint8 *pElem = pVars->inputStream.pBuffer + offset; |
| uint16 tmp1 = *(pElem++); |
| uint16 tmp2 = *(pElem); |
| |
| val = (tmp1 << 3); |
| val |= (tmp2 >> 5); |
| } |
| } |
| else |
| { |
| val = 0; // force mismatch |
| } |
| |
| if (val == SYNC_WORD) |
| { |
| pExt->inputBufferUsedLength = pVars->inputStream.usedBits >> 3; /// !!!!! |
| err = NO_DECODING_ERROR; |
| } |
| else |
| { |
| pExt->inputBufferCurrentLength = 0; |
| err = SYNCH_LOST_ERROR; |
| } |
| } |
| else |
| { |
| pExt->inputBufferCurrentLength = 0; |
| } |
| |
| return(err); |
| |
| } |
| |
| /* |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| |
| Description: |
| |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| pvmp3_header_sync |
| |
| Input |
| tmp3Bits *inputStream, structure holding the input stream parameters |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| search mp3 sync word |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| ------------------------------------------------------------------------------ |
| PSEUDO-CODE |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; FUNCTION CODE |
| ----------------------------------------------------------------------------*/ |
| |
| |
| ERROR_CODE pvmp3_header_sync(tmp3Bits *inputStream) |
| { |
| uint16 val; |
| uint32 availableBits = (inputStream->inputBufferCurrentLength << 3); // in bits |
| |
| // byte aligment |
| inputStream->usedBits = (inputStream->usedBits + 7) & 8; |
| |
| val = (uint16)getUpTo17bits(inputStream, SYNC_WORD_LNGTH); |
| |
| while (((val&SYNC_WORD) != SYNC_WORD) && (inputStream->usedBits < availableBits)) |
| { |
| val <<= 8; |
| val |= getUpTo9bits(inputStream, 8); |
| } |
| |
| if ((val&SYNC_WORD) == SYNC_WORD && (inputStream->usedBits < availableBits)) |
| { |
| return(NO_DECODING_ERROR); |
| } |
| else |
| { |
| return(SYNCH_LOST_ERROR); |
| } |
| |
| } |
| |