libMpegTPDec/src/tpdec_adts.cpp

/* -----------------------------------------------------------------------------
Software License for The Fraunhofer FDK AAC Codec Library for Android

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 1.    INTRODUCTION
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that implements the MPEG Advanced Audio Coding ("AAC") encoding and decoding
scheme for digital audio. This FDK AAC Codec software is intended to be used on
a wide variety of Android devices.

AAC's HE-AAC and HE-AAC v2 versions are regarded as today's most efficient
general perceptual audio codecs. AAC-ELD is considered the best-performing
full-bandwidth communications codec by independent studies and is widely
deployed. AAC has been standardized by ISO and IEC as part of the MPEG
specifications.

Patent licenses for necessary patent claims for the FDK AAC Codec (including
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Commercially-licensed AAC software libraries, including floating-point versions
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5.    CONTACT INFORMATION

Fraunhofer Institute for Integrated Circuits IIS
Attention: Audio and Multimedia Departments - FDK AAC LL
Am Wolfsmantel 33
91058 Erlangen, Germany

www.iis.fraunhofer.de/amm
amm-info@iis.fraunhofer.de
----------------------------------------------------------------------------- */

/******************* MPEG transport format decoder library *********************

   Author(s):   Josef Hoepfl

   Description: ADTS interface

*******************************************************************************/

#include "tpdec_adts.h"

#include "FDK_bitstream.h"

void adtsRead_CrcInit(
    HANDLE_ADTS pAdts) /*!< pointer to adts crc info stucture */
{
  FDKcrcInit(&pAdts->crcInfo, 0x8005, 0xFFFF, 16);
}

int adtsRead_CrcStartReg(
    HANDLE_ADTS pAdts,        /*!< pointer to adts stucture */
    HANDLE_FDK_BITSTREAM hBs, /*!< handle to current bit buffer structure */
    int mBits                 /*!< number of bits in crc region */
) {
  if (pAdts->bs.protection_absent) {
    return 0;
  }

  return (FDKcrcStartReg(&pAdts->crcInfo, hBs, mBits));
}

void adtsRead_CrcEndReg(
    HANDLE_ADTS pAdts,        /*!< pointer to adts crc info stucture */
    HANDLE_FDK_BITSTREAM hBs, /*!< handle to current bit buffer structure */
    int reg                   /*!< crc region */
) {
  if (pAdts->bs.protection_absent == 0) {
    FDKcrcEndReg(&pAdts->crcInfo, hBs, reg);
  }
}

TRANSPORTDEC_ERROR adtsRead_CrcCheck(HANDLE_ADTS pAdts) {
  TRANSPORTDEC_ERROR ErrorStatus = TRANSPORTDEC_OK;
  USHORT crc;

  if (pAdts->bs.protection_absent) return TRANSPORTDEC_OK;

  crc = FDKcrcGetCRC(&pAdts->crcInfo);
  if (crc != pAdts->crcReadValue) {
    return (TRANSPORTDEC_CRC_ERROR);
  }

  return (ErrorStatus);
}

#define Adts_Length_SyncWord 12
#define Adts_Length_Id 1
#define Adts_Length_Layer 2
#define Adts_Length_ProtectionAbsent 1
#define Adts_Length_Profile 2
#define Adts_Length_SamplingFrequencyIndex 4
#define Adts_Length_PrivateBit 1
#define Adts_Length_ChannelConfiguration 3
#define Adts_Length_OriginalCopy 1
#define Adts_Length_Home 1
#define Adts_Length_CopyrightIdentificationBit 1
#define Adts_Length_CopyrightIdentificationStart 1
#define Adts_Length_FrameLength 13
#define Adts_Length_BufferFullness 11
#define Adts_Length_NumberOfRawDataBlocksInFrame 2
#define Adts_Length_CrcCheck 16

TRANSPORTDEC_ERROR adtsRead_DecodeHeader(HANDLE_ADTS pAdts,
                                         CSAudioSpecificConfig *pAsc,
                                         HANDLE_FDK_BITSTREAM hBs,
                                         const INT ignoreBufferFullness) {
  INT crcReg;

  INT valBits;
  INT cmp_buffer_fullness;
  int i, adtsHeaderLength;

  STRUCT_ADTS_BS bs;

  CProgramConfig oldPce;
  /* Store the old PCE temporarily. Maybe we'll need it later if we
     have channelConfig=0 and no PCE in this frame. */
  FDKmemcpy(&oldPce, &pAsc->m_progrConfigElement, sizeof(CProgramConfig));

  valBits = FDKgetValidBits(hBs) + ADTS_SYNCLENGTH;

  if (valBits < ADTS_HEADERLENGTH) {
    return TRANSPORTDEC_NOT_ENOUGH_BITS;
  }

  /* adts_fixed_header */
  bs.mpeg_id = FDKreadBits(hBs, Adts_Length_Id);
  bs.layer = FDKreadBits(hBs, Adts_Length_Layer);
  bs.protection_absent = FDKreadBits(hBs, Adts_Length_ProtectionAbsent);
  bs.profile = FDKreadBits(hBs, Adts_Length_Profile);
  bs.sample_freq_index = FDKreadBits(hBs, Adts_Length_SamplingFrequencyIndex);
  bs.private_bit = FDKreadBits(hBs, Adts_Length_PrivateBit);
  bs.channel_config = FDKreadBits(hBs, Adts_Length_ChannelConfiguration);
  bs.original = FDKreadBits(hBs, Adts_Length_OriginalCopy);
  bs.home = FDKreadBits(hBs, Adts_Length_Home);

  /* adts_variable_header */
  bs.copyright_id = FDKreadBits(hBs, Adts_Length_CopyrightIdentificationBit);
  bs.copyright_start =
      FDKreadBits(hBs, Adts_Length_CopyrightIdentificationStart);
  bs.frame_length = FDKreadBits(hBs, Adts_Length_FrameLength);
  bs.adts_fullness = FDKreadBits(hBs, Adts_Length_BufferFullness);
  bs.num_raw_blocks =
      FDKreadBits(hBs, Adts_Length_NumberOfRawDataBlocksInFrame);
  bs.num_pce_bits = 0;

  adtsHeaderLength = ADTS_HEADERLENGTH;

  if (valBits < bs.frame_length * 8) {
    goto bail;
  }

  if (!bs.protection_absent) {
    FDKcrcReset(&pAdts->crcInfo);
    FDKpushBack(hBs, 56); /* complete fixed and variable header! */
    crcReg = FDKcrcStartReg(&pAdts->crcInfo, hBs, 0);
    FDKpushFor(hBs, 56);
  }

  if (!bs.protection_absent && bs.num_raw_blocks > 0) {
    if ((INT)FDKgetValidBits(hBs) < bs.num_raw_blocks * 16) {
      goto bail;
    }
    for (i = 0; i < bs.num_raw_blocks; i++) {
      pAdts->rawDataBlockDist[i] = (USHORT)FDKreadBits(hBs, 16);
      adtsHeaderLength += 16;
    }
    /* Change raw data blocks to delta values */
    pAdts->rawDataBlockDist[bs.num_raw_blocks] =
        bs.frame_length - 7 - bs.num_raw_blocks * 2 - 2;
    for (i = bs.num_raw_blocks; i > 0; i--) {
      pAdts->rawDataBlockDist[i] -= pAdts->rawDataBlockDist[i - 1];
    }
  }

  /* adts_error_check */
  if (!bs.protection_absent) {
    USHORT crc_check;

    FDKcrcEndReg(&pAdts->crcInfo, hBs, crcReg);

    if ((INT)FDKgetValidBits(hBs) < Adts_Length_CrcCheck) {
      goto bail;
    }

    crc_check = FDKreadBits(hBs, Adts_Length_CrcCheck);
    adtsHeaderLength += Adts_Length_CrcCheck;

    pAdts->crcReadValue = crc_check;
    /* Check header CRC in case of multiple raw data blocks */
    if (bs.num_raw_blocks > 0) {
      if (pAdts->crcReadValue != FDKcrcGetCRC(&pAdts->crcInfo)) {
        return TRANSPORTDEC_CRC_ERROR;
      }
      /* Reset CRC for the upcoming raw_data_block() */
      FDKcrcReset(&pAdts->crcInfo);
    }
  }

  /* check if valid header */
  if ((bs.layer != 0) ||            // we only support MPEG ADTS
      (bs.sample_freq_index >= 13)  // we only support 96kHz - 7350kHz
  ) {
    FDKpushFor(hBs, bs.frame_length * 8);  // try again one frame later
    return TRANSPORTDEC_UNSUPPORTED_FORMAT;
  }

  /* special treatment of id-bit */
  if ((bs.mpeg_id == 0) && (pAdts->decoderCanDoMpeg4 == 0)) {
    /* MPEG-2 decoder cannot play MPEG-4 bitstreams */

    FDKpushFor(hBs, bs.frame_length * 8);  // try again one frame later
    return TRANSPORTDEC_UNSUPPORTED_FORMAT;
  }

  if (!ignoreBufferFullness) {
    cmp_buffer_fullness =
        bs.frame_length * 8 +
        bs.adts_fullness * 32 * getNumberOfEffectiveChannels(bs.channel_config);

    /* Evaluate buffer fullness */
    if (bs.adts_fullness != 0x7FF) {
      if (pAdts->BufferFullnesStartFlag) {
        if (valBits < cmp_buffer_fullness) {
          /* Condition for start of decoding is not fulfilled */

          /* The current frame will not be decoded */
          FDKpushBack(hBs, adtsHeaderLength);

          if ((cmp_buffer_fullness + adtsHeaderLength) >
              (((8192 * 4) << 3) - 7)) {
            return TRANSPORTDEC_SYNC_ERROR;
          } else {
            return TRANSPORTDEC_NOT_ENOUGH_BITS;
          }
        } else {
          pAdts->BufferFullnesStartFlag = 0;
        }
      }
    }
  }

  /* Get info from ADTS header */
  AudioSpecificConfig_Init(pAsc);
  pAsc->m_aot = (AUDIO_OBJECT_TYPE)(bs.profile + 1);
  pAsc->m_samplingFrequencyIndex = bs.sample_freq_index;
  pAsc->m_samplingFrequency = SamplingRateTable[bs.sample_freq_index];
  pAsc->m_channelConfiguration = bs.channel_config;
  pAsc->m_samplesPerFrame = 1024;

  if (bs.channel_config == 0) {
    int pceBits = 0;
    UINT alignAnchor = FDKgetValidBits(hBs);

    if (FDKreadBits(hBs, 3) == ID_PCE) {
      /* Got luck! Parse the PCE */
      crcReg = adtsRead_CrcStartReg(pAdts, hBs, 0);

      CProgramConfig_Read(&pAsc->m_progrConfigElement, hBs, alignAnchor);

      adtsRead_CrcEndReg(pAdts, hBs, crcReg);
      pceBits = alignAnchor - FDKgetValidBits(hBs);
      /* store the number of PCE bits */
      bs.num_pce_bits = pceBits;
    } else {
      /* No PCE in this frame! Push back the ID tag bits. */
      FDKpushBack(hBs, 3);

      /* Encoders do not have to write a PCE in each frame.
         So if we already have a valid PCE we have to use it. */
      if (oldPce.isValid &&
          (bs.sample_freq_index ==
           pAdts->bs.sample_freq_index) /* we could compare the complete fixed
                                           header (bytes) here! */
          && (bs.channel_config == pAdts->bs.channel_config) /* == 0 */
          &&
          (bs.mpeg_id ==
           pAdts->bs.mpeg_id)) { /* Restore previous PCE which is still valid */
        FDKmemcpy(&pAsc->m_progrConfigElement, &oldPce, sizeof(CProgramConfig));
      } else if (bs.mpeg_id == 0) {
        /* If not it seems that we have a implicit channel configuration.
           This mode is not allowed in the context of ISO/IEC 14496-3.
           Skip this frame and try the next one. */
        FDKpushFor(hBs, (bs.frame_length << 3) - adtsHeaderLength - 3);
        return TRANSPORTDEC_UNSUPPORTED_FORMAT;
      }
      /* else {
         ISO/IEC 13818-7 implicit channel mapping is allowed.
         So just open the box of chocolates to see what we got.
      } */
    }
  }

  /* Copy bit stream data struct to persistent memory now, once we passed all
   * sanity checks above. */
  FDKmemcpy(&pAdts->bs, &bs, sizeof(STRUCT_ADTS_BS));

  return TRANSPORTDEC_OK;

bail:
  FDKpushBack(hBs, adtsHeaderLength);
  return TRANSPORTDEC_NOT_ENOUGH_BITS;
}

int adtsRead_GetRawDataBlockLength(HANDLE_ADTS pAdts, INT blockNum) {
  int length;

  if (pAdts->bs.num_raw_blocks == 0) {
    length =
        (pAdts->bs.frame_length - 7)
        << 3; /* aac_frame_length subtracted by the header size (7 bytes). */
    if (pAdts->bs.protection_absent == 0)
      length -= 16; /* substract 16 bit CRC */
  } else {
    if (pAdts->bs.protection_absent) {
      length = -1; /* raw data block length is unknown */
    } else {
      if (blockNum < 0 || blockNum > 3) {
        length = -1;
      } else {
        length = (pAdts->rawDataBlockDist[blockNum] << 3) - 16;
      }
    }
  }
  if (blockNum == 0 && length > 0) {
    length -= pAdts->bs.num_pce_bits;
  }
  return length;
}