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Diffstat (limited to 'media/libstagefright/codecs/mp3dec/src/pvmp3_decode_header.cpp')
| -rw-r--r-- | media/libstagefright/codecs/mp3dec/src/pvmp3_decode_header.cpp | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/media/libstagefright/codecs/mp3dec/src/pvmp3_decode_header.cpp b/media/libstagefright/codecs/mp3dec/src/pvmp3_decode_header.cpp new file mode 100644 index 0000000..d443b7c --- /dev/null +++ b/media/libstagefright/codecs/mp3dec/src/pvmp3_decode_header.cpp @@ -0,0 +1,194 @@ +/* ------------------------------------------------------------------ + * 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_decode_header.cpp + + Date: 09/21/2007 + +------------------------------------------------------------------------------ + REVISION HISTORY + + + Description: + +------------------------------------------------------------------------------ + INPUT AND OUTPUT DEFINITIONS + +Input + tbits *inputStream, bit stream + mp3Header *info, + uint32 *crc + Returns + + mp3Header *info, structure holding the parsed mp3 header info + uint32 *crc initialized crc computation + + +------------------------------------------------------------------------------ + FUNCTION DESCRIPTION + + gets mp3 header information + +------------------------------------------------------------------------------ + REQUIREMENTS + + +------------------------------------------------------------------------------ + REFERENCES + + [1] ISO MPEG Audio Subgroup Software Simulation Group (1996) + ISO 13818-3 MPEG-2 Audio Decoder - Lower Sampling Frequency Extension + +------------------------------------------------------------------------------ + PSEUDO-CODE + +------------------------------------------------------------------------------ +*/ + + +/*---------------------------------------------------------------------------- +; INCLUDES +----------------------------------------------------------------------------*/ + +#include "pvmp3_decode_header.h" +#include "pvmp3_crc.h" +#include "pvmp3_getbits.h" +#include "pvmp3_seek_synch.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_decode_header(tmp3Bits *inputStream, + mp3Header *info, + uint32 *crc) +{ + + ERROR_CODE err = NO_DECODING_ERROR; + uint32 temp; + + /* + * Verify that at least the header is complete + * Note that SYNC_WORD_LNGTH is in unit of bits, but inputBufferCurrentLength + * is in unit of bytes. + */ + if (inputStream->inputBufferCurrentLength < ((SYNC_WORD_LNGTH + 21) >> 3)) + { + return NO_ENOUGH_MAIN_DATA_ERROR; + } + + /* + * MPEG Audio Version ID + */ + temp = getUpTo17bits(inputStream, SYNC_WORD_LNGTH); + if ((temp & SYNC_WORD) != SYNC_WORD) + { + err = pvmp3_header_sync(inputStream); + + if (err != NO_DECODING_ERROR) + { + return err; + } + } + + temp = getNbits(inputStream, 21); // to avoid multiple bitstream accesses + + + switch (temp >> 19) /* 2 */ + { + case 0: + info->version_x = MPEG_2_5; + break; + case 2: + info->version_x = MPEG_2; + break; + case 3: + info->version_x = MPEG_1; + break; + default: + info->version_x = INVALID_VERSION; + err = UNSUPPORTED_LAYER; + break; + } + + info->layer_description = 4 - ((temp << 13) >> 30); /* 2 */ + info->error_protection = !((temp << 15) >> 31); /* 1 */ + + if (info->error_protection) + { + *crc = 0xffff; /* CRC start value */ + calculate_crc((temp << 16) >> 16, 16, crc); + } + + info->bitrate_index = (temp << 16) >> 28; /* 4 */ + info->sampling_frequency = (temp << 20) >> 30; /* 2 */ + info->padding = (temp << 22) >> 31; /* 1 */ + info->extension = (temp << 23) >> 31; /* 1 */ + info->mode = (temp << 24) >> 30; /* 2 */ + info->mode_ext = (temp << 26) >> 30; /* 2 */ + info->copyright = (temp << 27) >> 31; /* 1 */ + info->original = (temp << 28) >> 31; /* 1 */ + info->emphasis = (temp << 30) >> 30; /* 2 */ + + + if (!info->bitrate_index || info->sampling_frequency == 3) + { + err = UNSUPPORTED_FREE_BITRATE; + } + + return(err); +} + |