; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/
-#define FIND_ADTS_ERROR -1
/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
UInt32 test_for_syncword;
UInt32 syncword = *(pSyncword);
+
/*
* Determine the maximum number of bits available to this function for
* the syncword search.
test_for_syncword ^= syncword;
/*
- * Scan bit-by-bit through the bitstream, until the function either
- * runs out of bits, or finds the syncword.
+ * Scan byte-by-byte through the bitstream, until the function either
+ * runs out of bytes, or finds the syncword.
*/
while ((test_for_syncword != 0) && (search_length > 0))
{
- search_length--;
+ search_length -= 8;
- adts_header <<= 1;
- adts_header |= getbits(1, pInputStream);
+ adts_header <<= 8;
+ adts_header |= get9_n_lessbits(8, pInputStream);
test_for_syncword = adts_header & syncword_mask;
test_for_syncword ^= syncword;
}
- if (search_length == 0)
+ if (search_length <= 0)
{
- status = FIND_ADTS_ERROR;
+ status = MP4AUDEC_LOST_FRAME_SYNC;
}
- /*
- * Return the syncword's position in the bitstream. Correct placement
- * of the syncword will result in byte_align_offset == 0.
- * If the syncword is found not to be byte-aligned, then return
- * the degree of disalignment, so further decoding can
- * be shifted as necessary.
- *
- */
- pInputStream->byteAlignOffset =
- (pInputStream->usedBits - syncword_length) & 0x7;
+ *(pSyncword) = adts_header;
} /* END if (pInputStream->usedBits < ...) */
-
else
{
- status = FIND_ADTS_ERROR;
+ status = MP4AUDEC_LOST_FRAME_SYNC;
}
- *(pSyncword) = adts_header;
-
return (status);
} /* find_adts_syncword() */
+
+
+
+/*----------------------------------------------------------------------------
+ FUNCTION DESCRIPTION
+
+ This module get the distance in bytes between the current and next sync word
+ then compare the content of the fix header (28 bits).
+
+ If no match is found, the function returns
+ status == MP4AUDEC_LOST_FRAME_SYNC, and reset the success counter *pInvoke
+
+------------------------------------------------------------------------------
+ INPUT AND OUTPUT DEFINITIONS
+
+ Inputs:
+
+ adts_var_header 28 bit content of the variable part of the adts header
+ [UInt32]
+
+ pSyncword = Pointer to variable containing the syncword that the
+ function should be scanning for in the buffer. [ UInt32 * ]
+
+ pInputStream = Pointer to a BITS structure, used by the function getbits
+ to retrieve data from the bitstream. [ BITS * ]
+
+ pInvoke = Pointer holding the success adts counter. [ Int * ]
+
+
+----------------------------------------------------------------------------*/
+
+/*----------------------------------------------------------------------------
+; FUNCTION CODE
+----------------------------------------------------------------------------*/
+
+
+Int validate_adts_syncword(
+ UInt32 adts_var_header,
+ UInt32 *pSyncword,
+ BITS *pInputStream,
+ Int *pInvoke)
+{
+
+ UInt32 frame_length;
+ UInt32 tmp;
+ Int status = SUCCESS;
+
+ /*
+ * frame_length is a 13-bit field which indicates the length,
+ * in bytes, of the frame including error_check and headers.
+ * This information can theoretically be used to help verify syncwords.
+ * adts_var_header is 28 bits long, need to remove 13-bit conformed by
+ * buffer fullnes and headerless frame info , and mask the rest
+ */
+ frame_length = ((UInt)(adts_var_header >> 13)) & 0x1FFF;
+
+ /* push current location, to validate 2 consecutive sync words */
+ tmp = pInputStream->usedBits;
+
+ /* Jump to next sync word, based on info on the header */
+ pInputStream->usedBits += (frame_length << 3)
+ - LENGTH_FIXED_HEADER - LENGTH_VARIABLE_HEADER;
+
+
+ if ((Int)pInputStream->usedBits <
+ ((Int)pInputStream->availableBits - LENGTH_FIXED_HEADER))
+ {
+ uint32 temp = getbits(LENGTH_FIXED_HEADER, pInputStream);
+ /*
+ * Check if fixed header in the very next predicted frame matches
+ */
+ if ((*(pSyncword) & MASK_28BITS) != temp)
+ {
+ *(pInvoke) = 0; /* reset valid adts frame counter */
+ status = MP4AUDEC_LOST_FRAME_SYNC; /* no match means a false lock on sync word */
+ }
+ }
+ else
+ {
+ status = MP4AUDEC_LOST_FRAME_SYNC; /* no match means a false lock on sync word */
+ }
+ /* pop current location */
+ pInputStream->usedBits = tmp;
+
+ return (status);
+
+} /* validate_adts_syncword() */
+
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/
-#define LENGTH_VARIABLE_HEADER 28
-#define LENGTH_FIXED_HEADER 28
-#define LENGTH_SYNCWORD 15
-#define LENGTH_CRC 16
-
-#define ID_BIT_FILTER 0x7FFB
-#define SYNCWORD_15BITS 0x7FF8
-#define MASK_28BITS 0x0FFFFFFFL
+#define NUM_OF_TRIES (5)
/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
Int CorrectlyReadFramesCount)
{
UInt32 adts_header;
+ UInt32 adts_var_header = 0;
UInt lower_16;
- Int status = SUCCESS;
+ Int status = MP4AUDEC_LOST_FRAME_SYNC;
UInt channel_configuration;
+
/*
- * Search for the LONG ADTS syncword (comprised of the entire fixed header)
- * if the number of CorrectlyReadFrames is > CorrectlyReadFramesCount
- *
- * Otherwise, search for just the short syncword.
+ * Loop NUM_OF_TRIES times until succesfully locking into a sync word
+ * Success requires match and validation.
+ * Search is done over the available buffered data.
*/
- if (*(pInvoke) > CorrectlyReadFramesCount)
+ for (int k = 0 ; ((k < NUM_OF_TRIES) && (status != SUCCESS)); k++)
{
- /*
- * Find the long ADTS syncword
- * (comprised of the entire ADTS fixed header)
- */
-
- status = find_adts_syncword(pSyncword,
- &(pVars->inputStream),
- LENGTH_FIXED_HEADER,
- MASK_28BITS);
- }
- else
- {
-
- *(pSyncword) = SYNCWORD_15BITS;
-
- status = find_adts_syncword(pSyncword,
- &(pVars->inputStream),
- LENGTH_SYNCWORD,
- ID_BIT_FILTER);
-
- /*
- * Extract the data from the header following the syncword
- */
- adts_header = getbits((LENGTH_FIXED_HEADER - LENGTH_SYNCWORD),
- &(pVars->inputStream));
-
- *(pSyncword) <<= (LENGTH_FIXED_HEADER - LENGTH_SYNCWORD);
- *(pSyncword) |= adts_header;
-
- /* Denotes whether a CRC check should be performed */
- pVars->prog_config.CRC_absent = ((UInt)(adts_header >> 12)) & 0x0001;
-
- /*
- * All the unread bits in adts_header reside in the lower
- * 16-bits at this point. Perform a typecast for faster
- * execution on 16-bit processors.
- */
- lower_16 = (UInt)adts_header;
-
- /*
- * Profile consists of 2 bits, which indicate
- * the profile used.
- *
- * '00' AAC_MAIN profile
- * '01' AAC_LC (Low Complexity) profile
- * '10' AAC_SSR (Scaleable Sampling Rate) profile
- * '11' AAC_LTP (Long Term Prediction) profile
- */
- pVars->prog_config.profile = (lower_16 >> 10) & 0x3;
-
- if (((pVars->prog_config.profile + 1) == MP4AUDIO_AAC_SSR) ||
- ((pVars->prog_config.profile + 1) == MP4AUDIO_AAC_MAIN))
- {
- status = 1; /* Not supported, only LC and LTP */
- }
+ status = SUCCESS;
/*
- * Sampling_rate_idx consists of 4 bits
- * see Ref #1 for their interpretation.
+ * Sync words are always byte aligned
*/
- pVars->prog_config.sampling_rate_idx = (lower_16 >> 6) & 0xF;
+ byte_align(&(pVars->inputStream));
/*
- * private_bit is a bit for private use. ISO/IEC will not make
- * use of this bit in the future.
+ * Search for the LONG ADTS syncword (comprised of the entire fixed header)
+ * if the number of CorrectlyReadFrames is > CorrectlyReadFramesCount
*
- * We currently make no use of it, but parsing the information
- * from the bitstream could be easily implemented with the
- * following instruction...
- *
- * private_bit = (lower_16 & 0x0400) >> 10;
+ * Otherwise, search for just the short syncword.
*/
-
- /*
- * These 3 bits indicate the channel configuration used.
- *
- * If '0' then the channel configuration is unspecified here,
- * and must be given by a program configuration element in
- * the raw data block.
- *
- * If '1' then the channel configuration is MONO.
- * If '2' then the channel configuration is STEREO
- *
- * 3-7 represent channel configurations which this library
- * will not support in the forseeable future.
- */
- channel_configuration = (lower_16 >> 2) & 0x7;
- /* do not support more than 2 channels */
- if (channel_configuration > 2)
+ if (*(pInvoke) > CorrectlyReadFramesCount)
{
- status = 1;
+ /*
+ * Find the long ADTS syncword
+ * (comprised of the entire ADTS fixed header)
+ */
+
+ status = find_adts_syncword(pSyncword,
+ &(pVars->inputStream),
+ LENGTH_FIXED_HEADER,
+ MASK_28BITS);
+
+ if (status == MP4AUDEC_LOST_FRAME_SYNC)
+ {
+ break; /* No sync word found in the available data */
+ }
+
+ /* Grab the bits in the ADTS variable header */
+ adts_var_header = getbits(LENGTH_VARIABLE_HEADER, &(pVars->inputStream));
+
+ /*
+ * Validate sync word by checking next header a the distance specified in
+ * the current header
+ */
+ status = validate_adts_syncword(adts_var_header,
+ pSyncword,
+ &(pVars->inputStream),
+ pInvoke);
+
+ if (status == MP4AUDEC_LOST_FRAME_SYNC)
+ {
+ pVars->inputStream.usedBits -= LENGTH_VARIABLE_HEADER;
+
+ continue; /* No sync word could be validated, keep searching long sync word */
+ }
}
-
- /*
- * The following 2 bits encode copyright information.
- * original_copy is '0' if there is no copyright in the bitstream.
- * '1' if the bitstream is copyright protected.
- *
- * home is '0' for a copy, '1' for an original.
- *
- * PacketVideo currently does nothing with this information,
- * however, parsing the data from the bitstream could be easily
- * implemented with the following instructions...
- *
- * original_copy = (lower_16 >> 1) & 0x1;
- *
- * home = (lower_16 & 0x1);
- *
- */
-
- /* Set up based on information extracted from the ADTS FIXED header */
-
- /* This equals 1 for STEREO, 0 for MONO */
- if (channel_configuration)
- {
- channel_configuration--;
- }
- pVars->prog_config.front.ele_is_cpe[0] = channel_configuration;
-
- /* This value is constant for both MONO and STEREO */
- pVars->prog_config.front.num_ele = 1;
-
- /* ADTS does not specify this tag value - do we even use it? */
- pVars->prog_config.front.ele_tag[0] = 0;
-
- /* Disable all mix related variables */
- pVars->prog_config.mono_mix.present = 0;
- pVars->prog_config.stereo_mix.present = 0;
- pVars->prog_config.matrix_mix.present = 0;
-
- /* enter configuration into MC_Info structure */
- if (status == SUCCESS)
+ else
{
- /* profile + 1 == audioObjectType */
- status =
- set_mc_info(
- &(pVars->mc_info),
- (tMP4AudioObjectType)(pVars->prog_config.profile + 1),
- pVars->prog_config.sampling_rate_idx,
- pVars->prog_config.front.ele_tag[0],
- pVars->prog_config.front.ele_is_cpe[0],
- pVars->winmap, /* changed from pVars->pWinSeqInfo, */
- pVars->SFBWidth128);
- } /* if (status == SUCCESS) */
+ *(pSyncword) = SYNCWORD_15BITS;
+
+ status = find_adts_syncword(pSyncword,
+ &(pVars->inputStream),
+ LENGTH_SYNCWORD,
+ ID_BIT_FILTER);
+
+ if (status == MP4AUDEC_LOST_FRAME_SYNC)
+ {
+ break; /* No sync word found in the available data */
+ }
+
+ /*
+ * Extract the data from the header following the syncword
+ */
+ adts_header = getbits((LENGTH_FIXED_HEADER - LENGTH_SYNCWORD),
+ &(pVars->inputStream));
+
+ /* Assembling possible long ADTS syncword */
+ *(pSyncword) <<= (LENGTH_FIXED_HEADER - LENGTH_SYNCWORD);
+ *(pSyncword) |= adts_header;
+
+ /* Grab the bits in the ADTS variable header */
+ adts_var_header = getbits(LENGTH_VARIABLE_HEADER, &(pVars->inputStream));
+
+ /*
+ * Validate sync word by checking next header a the distance specified in
+ * the current header
+ */
+
+ status = validate_adts_syncword(adts_var_header,
+ pSyncword,
+ &(pVars->inputStream),
+ pInvoke);
+
+ if (status == MP4AUDEC_LOST_FRAME_SYNC)
+ {
+ pVars->inputStream.usedBits -= (LENGTH_VARIABLE_HEADER + LENGTH_SYNCWORD);
+
+ continue; /* No sync word could be validated, keep searching initial sync word */
+ }
+
+
+ /* Denotes whether a CRC check should be performed 1 == NO, 0 == YES */
+ pVars->prog_config.CRC_absent =
+ ((UInt)(*(pSyncword) >> (LENGTH_FIXED_HEADER - LENGTH_SYNCWORD))) & 1;
+
+ /*
+ * All the unread bits in adts_header reside in the lower
+ * 16-bits at this point. Perform a typecast for faster
+ * execution on 16-bit processors.
+ */
+ lower_16 = (UInt)adts_header;
+
+ /*
+ * Profile consists of 2 bits, which indicate
+ * the profile used.
+ *
+ * '00' AAC_MAIN profile
+ * '01' AAC_LC (Low Complexity) profile
+ * '10' AAC_SSR (Scaleable Sampling Rate) profile
+ * '11' AAC_LTP (Long Term Prediction) profile
+ */
+ pVars->prog_config.profile = (lower_16 >> 10) & 0x3;
+
+ if ((pVars->prog_config.profile + 1) == MP4AUDIO_AAC_SSR ||
+ (pVars->prog_config.profile + 1) == MP4AUDIO_AAC_MAIN)
+ {
+ status = 1; /* Not supported */
+ }
+
+ /*
+ * Sampling_rate_idx consists of 4 bits
+ * see Ref #1 for their interpretation.
+ */
+ pVars->prog_config.sampling_rate_idx = (lower_16 >> 6) & 0xF;
+
+ /*
+ * private_bit is a bit for private use. ISO/IEC will not make
+ * use of this bit in the future.
+ *
+ * We currently make no use of it, but parsing the information
+ * from the bitstream could be easily implemented with the
+ * following instruction...
+ *
+ * private_bit = (lower_16 & 0x0400) >> 10;
+ */
+
+ /*
+ * These 3 bits indicate the channel configuration used.
+ *
+ * If '0' then the channel configuration is unspecified here,
+ * and must be given by a program configuration element in
+ * the raw data block.
+ *
+ * If '1' then the channel configuration is MONO.
+ * If '2' then the channel configuration is STEREO
+ *
+ * 3-7 represent channel configurations which this library
+ * will not support in the forseeable future.
+ */
+ channel_configuration = (lower_16 >> 2) & 0x7;
+ /* do not support more than 2 channels */
+ if (channel_configuration > 2)
+ {
+ status = 1;
+ }
+
+ /*
+ * The following 2 bits encode copyright information.
+ * original_copy is '0' if there is no copyright in the bitstream.
+ * '1' if the bitstream is copyright protected.
+ *
+ * home is '0' for a copy, '1' for an original.
+ *
+ * PacketVideo currently does nothing with this information,
+ * however, parsing the data from the bitstream could be easily
+ * implemented with the following instructions...
+ *
+ * original_copy = (lower_16 >> 1) & 0x1;
+ *
+ * home = (lower_16 & 0x1);
+ *
+ */
+
+ /* Set up based on information extracted from the ADTS FIXED header */
+
+ /* This equals 1 for STEREO, 0 for MONO */
+ if (channel_configuration)
+ {
+ channel_configuration--;
+ }
+ pVars->prog_config.front.ele_is_cpe[0] = channel_configuration;
+
+ /* This value is constant for both MONO and STEREO */
+ pVars->prog_config.front.num_ele = 1;
+
+ /* ADTS does not specify this tag value - do we even use it? */
+ pVars->prog_config.front.ele_tag[0] = 0;
+
+ /* Disable all mix related variables */
+ pVars->prog_config.mono_mix.present = 0;
+ pVars->prog_config.stereo_mix.present = 0;
+ pVars->prog_config.matrix_mix.present = 0;
+
+ /* enter configuration into MC_Info structure */
+ if (status == SUCCESS)
+ {
+ /* profile + 1 == audioObjectType */
+ status = set_mc_info(
+ &(pVars->mc_info),
+ (tMP4AudioObjectType)(pVars->prog_config.profile + 1),
+ pVars->prog_config.sampling_rate_idx,
+ pVars->prog_config.front.ele_tag[0],
+ pVars->prog_config.front.ele_is_cpe[0],
+ pVars->winmap, /* changed from pVars->pWinSeqInfo, */
+ pVars->SFBWidth128);
+
+ } /* if (status == SUCCESS) */
#ifdef AAC_PLUS
- /*
- * For implicit signalling, no hint that sbr or ps is used, so we need to
- * check the sampling frequency of the aac content, if lesser or equal to
- * 24 KHz, by defualt upsample, otherwise, do nothing
- */
- if ((pVars->prog_config.sampling_rate_idx >= 6) && (pVars->aacPlusEnabled == TRUE))
- {
- pVars->mc_info.upsamplingFactor = 2;
- pVars->prog_config.sampling_rate_idx -= 3;
- pVars->mc_info.sbrPresentFlag = 1;
- pVars->sbrDecoderData.SbrChannel[0].syncState = SBR_ACTIVE;
- pVars->sbrDecoderData.SbrChannel[1].syncState = SBR_ACTIVE;
- }
+ /* default as adts has limited number of bits and can't carry this info */
+ pVars->mc_info.ExtendedAudioObjectType = pVars->mc_info.audioObjectType; /* default */
+
+ /*
+ * For implicit signalling, no hint that sbr or ps is used, so we need to
+ * check the sampling frequency of the aac content, if lesser or equal to
+ * 24 KHz, by defualt upsample, otherwise, do nothing
+ */
+ if ((pVars->prog_config.sampling_rate_idx >= 6) && (pVars->aacPlusEnabled == TRUE))
+ {
+ pVars->mc_info.upsamplingFactor = 2;
+ pVars->prog_config.sampling_rate_idx -= 3;
+ pVars->mc_info.sbrPresentFlag = 1;
+ pVars->sbrDecoderData.SbrChannel[0].syncState = SBR_ACTIVE;
+ pVars->sbrDecoderData.SbrChannel[1].syncState = SBR_ACTIVE;
+ }
#endif
+ /*
+ * This keeps track of how many headers have been read in the file.
+ * After the three successful headers with the same configuration
+ * are read in, the entire ADTS fixed header is used as the syncword
+ * for a more robust 28-bit long syncword
+ */
+
+ if (status == SUCCESS)
+ {
+ (*pInvoke)++;
+ }
+ else
+ {
+ (*pInvoke) = 0;
+ }
+
+ } /* END if (*(pInvoke) > 3) */
+ }
- /*
- * The tag and is_cpe will be checked in huffdecode,
- * remove this check routine.
- */
- /*if (status == SUCCESS)
- *{
- * if ( (*pInvoke) != 0)
- * {
- * status =
- * check_mc_info(
- * &(pVars->mc_info),
- * &(pVars->savedMCInfo),
- * FALSE);
- * }
- * else
- * {
- * status =
- * check_mc_info(
- * &(pVars->mc_info),
- * &(pVars->savedMCInfo),
- * TRUE);
- * }
- *
- *}*/ /* if (status == SUCCESS) */
-
- /*
- * This keeps track of how many headers have been read in the file.
- * After the three successful headers with the same configuration
- * are read in, the entire ADTS fixed header is used as the syncword
- * for a more robust 28-bit long syncword
- */
-
- if (status == SUCCESS)
- {
- (*pInvoke)++;
- }
- else
- {
- (*pInvoke) = 0;
- }
-
- } /* END if (*(pInvoke) > 3) */
-
- /* Grab the bits in the ADTS variable header */
- adts_header = getbits(
- LENGTH_VARIABLE_HEADER,
- &(pVars->inputStream));
/*
* copyright_identification bit is a single bit of the 72-bit
* copyright_id field. This consists of a 8-bit copyright identifier
* copyright_id_start = ((UInt)(adts_header >> 26)) & 0x1;
*/
- /*
- * frame_length is a 13-bit field which indicates the length,
- * in bytes, of the frame including error_check and headers.
- * This information can theoretically be used to help verify syncwords.
- */
- pVars->prog_config.frame_length = ((UInt)(adts_header >> 13)) & 0x1FFF;
/*
* All the unread bits in adts_header reside in the lower
* 16-bits at this point. Perform a typecast for faster
* execution on 16-bit processors.
*/
- lower_16 = (UInt)adts_header;
+ lower_16 = (UInt)adts_var_header;
/*
* Indicates the number of 32-bit words remaining in the
if (pVars->prog_config.CRC_absent == 0)
{
- pVars->prog_config.CRC_check = (UInt)getbits(
- LENGTH_CRC,
- &(pVars->inputStream));
+ pVars->prog_config.CRC_check = (UInt)getbits(LENGTH_CRC,
+ &(pVars->inputStream));
}
- /* pVars->current_program = 0; */ /* shall be set after PCE is read */
-
return (status);
} /* END get_adts_header */
+
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