libwebp/src/vp8.c

// Copyright 2010 Google Inc.
//
// This code is licensed under the same terms as WebM:
//  Software License Agreement:  http://www.webmproject.org/license/software/
//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
// -----------------------------------------------------------------------------
//
// main entry for the decoder
//
// Author: Skal (pascal.massimino@gmail.com)

#include <stdlib.h>
#include "vp8i.h"

//-----------------------------------------------------------------------------
// VP8Decoder

static void SetOk(VP8Decoder* const dec) {
  dec->status_ = 0;
  dec->error_msg_ = "OK";
}

void VP8InitIo(VP8Io* const io) {
  if (io) {
    memset(io, 0, sizeof(*io));
  }
}

VP8Decoder* VP8New() {
  VP8Decoder* dec = (VP8Decoder*)calloc(1, sizeof(VP8Decoder));
  if (dec) {
    SetOk(dec);
    dec->ready_ = 0;
  }
  return dec;
}

int VP8Status(VP8Decoder* const dec) {
  if (!dec) return 2;
  return dec->status_;
}

const char* VP8StatusMessage(VP8Decoder* const dec) {
  if (!dec) return "no object";
  if (!dec->error_msg_) return "OK";
  return dec->error_msg_;
}

void VP8Delete(VP8Decoder* const dec) {
  if (dec) {
    VP8Clear(dec);
    free(dec);
  }
}

int VP8SetError(VP8Decoder* const dec, int error, const char *msg) {
  dec->status_ = error;
  dec->error_msg_ = msg;
  dec->ready_ = 0;
  return 0;
}

//-----------------------------------------------------------------------------
// Header parsing

static void ResetSegmentHeader(VP8SegmentHeader* const hdr) {
  assert(hdr);
  hdr->use_segment_ = 0;
  hdr->update_map_ = 0;
  hdr->absolute_delta_ = 1;
  memset(hdr->quantizer_, 0, sizeof(hdr->quantizer_));
  memset(hdr->filter_strength_, 0, sizeof(hdr->filter_strength_));
}

// Paragraph 9.3
static int ParseSegmentHeader(VP8BitReader* br,
                              VP8SegmentHeader* hdr, VP8Proba* proba) {
  assert(br);
  assert(hdr);
  hdr->use_segment_ = VP8Get(br);
  if (hdr->use_segment_) {
    hdr->update_map_ = VP8Get(br);
    const int update_data = VP8Get(br);
    if (update_data) {
      hdr->absolute_delta_ = VP8Get(br);
      for (int s = 0; s < NUM_MB_SEGMENTS; ++s) {
        hdr->quantizer_[s] = VP8Get(br) ? VP8GetSignedValue(br, 7) : 0;
      }
      for (int s = 0; s < NUM_MB_SEGMENTS; ++s) {
        hdr->filter_strength_[s] = VP8Get(br) ? VP8GetSignedValue(br, 6) : 0;
      }
    }
    if (hdr->update_map_) {
      for (int s = 0; s < MB_FEATURE_TREE_PROBS; ++s) {
        proba->segments_[s] = VP8Get(br) ? VP8GetValue(br, 8) : 255u;
      }
    }
  } else {
    hdr->update_map_ = 0;
  }
  return 1;
}

// Paragraph 9.5
static int ParsePartitions(VP8Decoder* const dec,
                           const uint8_t* buf, uint32_t size) {
  VP8BitReader* const br = &dec->br_;
  dec->num_parts_ = 1 << VP8GetValue(br, 2);
  const uint8_t* sz = buf;
  const int last_part = dec->num_parts_ - 1;
  uint32_t offset = last_part * 3;
  if (size <= offset) {
    return 0;
  }
  for (int p = 0; p < last_part; ++p) {
    const uint32_t psize = sz[0] | (sz[1] << 8) | (sz[2] << 16);
    if (offset + psize > size) {
      return 0;
    }
    VP8Init(dec->parts_ + p, buf + offset, psize);
    offset += psize;
    sz += 3;
  }
  size -= offset;
  VP8Init(dec->parts_ + last_part, buf + offset, size);
  return 1;
}

// Paragraph 9.4
static int ParseFilterHeader(VP8BitReader* br, VP8Decoder* const dec) {
  VP8FilterHeader* const hdr = &dec->filter_hdr_;
  hdr->simple_    = VP8Get(br);
  hdr->level_     = VP8GetValue(br, 6);
  hdr->sharpness_ = VP8GetValue(br, 3);
  hdr->use_lf_delta_ = VP8Get(br);
  if (hdr->use_lf_delta_) {
    if (VP8Get(br)) {   // update lf-delta?
      for (int i = 0; i < NUM_REF_LF_DELTAS; ++i) {
        if (VP8Get(br)) {
          hdr->ref_lf_delta_[i] = VP8GetSignedValue(br, 6);
        }
      }
      for (int i = 0; i < NUM_MODE_LF_DELTAS; ++i) {
        if (VP8Get(br)) {
          hdr->mode_lf_delta_[i] = VP8GetSignedValue(br, 6);
        }
      }
    }
  }
  dec->filter_type_ = (hdr->level_ == 0) ? 0 : hdr->simple_ ? 1 : 2;
  if (dec->filter_type_ > 0) {    // precompute filter levels per segment
    if (dec->segment_hdr_.use_segment_) {
      for (int s = 0; s < NUM_MB_SEGMENTS; ++s) {
        int strength = dec->segment_hdr_.filter_strength_[s];
        if (!dec->segment_hdr_.absolute_delta_) {
          strength += hdr->level_;
        }
        dec->filter_levels_[s] = strength;
      }
    } else {
      dec->filter_levels_[0] = hdr->level_;
    }
  }
  return 1;
}

static inline uint32_t get_le32(const uint8_t* const data) {
  return data[0] | (data[1] << 8) | (data[2] << 16) | (data[3] << 24);
}

// Topmost call
int VP8GetHeaders(VP8Decoder* const dec, VP8Io* const io) {
  if (dec == NULL) {
    return 0;
  }
  SetOk(dec);
  if (io == NULL || io->data == NULL || io->data_size <= 4) {
    return VP8SetError(dec, 2, "null VP8Io passed to VP8GetHeaders()");
  }
  const uint8_t* buf = io->data;
  uint32_t buf_size = io->data_size;
  if (buf_size < 4) {
    return VP8SetError(dec, 2, "Not enough data to parse frame header");
  }

  // Skip over valid RIFF headers
  if (!memcmp(buf, "RIFF", 4)) {
    if (buf_size < 20 + 4) {
      return VP8SetError(dec, 2, "RIFF: Truncated header.");
    }
    if (memcmp(buf + 8, "WEBP", 4)) {   // wrong image file signature
      return VP8SetError(dec, 2, "RIFF: WEBP signature not found.");
    }
    const uint32_t riff_size = get_le32(buf + 4);
    if (memcmp(buf + 12, "VP8 ", 4)) {
      return VP8SetError(dec, 2, "RIFF: Invalid compression format.");
    }
    const uint32_t chunk_size = get_le32(buf + 16);
    if ((chunk_size > riff_size + 8) || (chunk_size & 1)) {
      return VP8SetError(dec, 2, "RIFF: Inconsistent size information.");
    }
    buf += 20;
    buf_size -= 20;
  }

  // Paragraph 9.1
  VP8FrameHeader* const frm_hdr = &dec->frm_hdr_;
  const uint32_t bits = buf[0] | (buf[1] << 8) | (buf[2] << 16);
  frm_hdr->key_frame_ = !(bits & 1);
  frm_hdr->profile_ = (bits >> 1) & 7;
  frm_hdr->show_ = (bits >> 4) & 1;
  frm_hdr->partition_length_ = (bits >> 5);
  buf += 3;
  buf_size -= 3;

  VP8PictureHeader* const pic_hdr = &dec->pic_hdr_;
  if (frm_hdr->key_frame_) {
    // Paragraph 9.2
    if (buf_size < 7) {
      return VP8SetError(dec, 2, "cannot parse picture header");
    }
    if (buf[0] != 0x9d || buf[1] != 0x01 || buf[2] != 0x2a) {
      return VP8SetError(dec, 2, "Bad code word");
    }
    pic_hdr->width_ = ((buf[4] << 8) | buf[3]) & 0x3fff;
    pic_hdr->xscale_ = buf[4] >> 6;   // ratio: 1, 5/4 5/3 or 2
    pic_hdr->height_ = ((buf[6] << 8) | buf[5]) & 0x3fff;
    pic_hdr->yscale_ = buf[6] >> 6;
    buf += 7;
    buf_size -= 7;

    dec->mb_w_ = (pic_hdr->width_ + 15) >> 4;
    dec->mb_h_ = (pic_hdr->height_ + 15) >> 4;
    io->width = pic_hdr->width_;
    io->height = pic_hdr->height_;

    VP8ResetProba(&dec->proba_);
    ResetSegmentHeader(&dec->segment_hdr_);
    dec->segment_ = 0;    // default for intra
  }

  VP8BitReader* const br = &dec->br_;
  VP8Init(br, buf, buf_size);
  buf += frm_hdr->partition_length_;
  buf_size -= frm_hdr->partition_length_;
  if (frm_hdr->key_frame_) {
    pic_hdr->colorspace_ = VP8Get(br);
    pic_hdr->clamp_type_ = VP8Get(br);
  }
  if (!ParseSegmentHeader(br, &dec->segment_hdr_, &dec->proba_)) {
    return VP8SetError(dec, 2, "cannot parse segment header");
  }
  // Filter specs
  if (!ParseFilterHeader(br, dec)) {
    return VP8SetError(dec, 2, "cannot parse filter header");
  }
  if (!ParsePartitions(dec, buf, buf_size)) {
    return VP8SetError(dec, 2, "cannot parse partitions");
  }

  // quantizer change
  VP8ParseQuant(dec);

  // Frame buffer marking
  if (!frm_hdr->key_frame_) {
    // Paragraph 9.7
#ifndef ONLY_KEYFRAME_CODE
    dec->buffer_flags_ = VP8Get(br) << 0;   // update golden
    dec->buffer_flags_ |= VP8Get(br) << 1;  // update alt ref
    if (!(dec->buffer_flags_ & 1)) {
      dec->buffer_flags_ |= VP8GetValue(br, 2) << 2;
    }
    if (!(dec->buffer_flags_ & 2)) {
      dec->buffer_flags_ |= VP8GetValue(br, 2) << 4;
    }
    dec->buffer_flags_ |= VP8Get(br) << 6;    // sign bias golden
    dec->buffer_flags_ |= VP8Get(br) << 7;    // sign bias alt ref
#else
    return VP8SetError(dec, 2, "Not a key frame.");
#endif
  } else {
    dec->buffer_flags_ = 0x003 | 0x100;
  }

  // Paragraph 9.8
  dec->update_proba_ = VP8Get(br);
  if (!dec->update_proba_) {    // save for later restore
    dec->proba_saved_ = dec->proba_;
  }

#ifndef ONLY_KEYFRAME_CODE
  dec->buffer_flags_ &= 1 << 8;
  dec->buffer_flags_ |=
      (frm_hdr->key_frame_ || VP8Get(br)) << 8;    // refresh last frame
#endif

  VP8ParseProba(br, dec);

  // sanitized state
  dec->ready_ = 1;
  return 1;
}

//-----------------------------------------------------------------------------
// Residual decoding (Paragraph 13.2 / 13.3)

static const uint8_t kBands[16 + 1] = {
  0, 1, 2, 3, 6, 4, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7,
  0  // extra entry as sentinel
};

static const uint8_t kCat3[] = {173, 148, 140, 0};
static const uint8_t kCat4[] = {176, 155, 140, 135, 0};
static const uint8_t kCat5[] = {180, 157, 141, 134, 130, 0};
static const uint8_t kCat6[] =
  {254, 254, 243, 230, 196, 177, 153, 140, 133, 130, 129, 0};
static const uint8_t * const kCat3456[] = { kCat3, kCat4, kCat5, kCat6 };
static const uint8_t kZigzag[16] = {
  0, 1, 4, 8,  5, 2, 3, 6,  9, 12, 13, 10,  7, 11, 14, 15
};

typedef const uint8_t PROBA_ARRAY[NUM_CTX][NUM_PROBAS];

static int GetCoeffs(VP8BitReader* const br,
                     const uint8_t (*prob)[NUM_CTX][NUM_PROBAS],
                     int ctx, const uint16_t dq[2], int n, int16_t* out) {
  const uint8_t* p = prob[kBands[n]][ctx];
  if (!VP8GetBit(br, p[0])) {   // first EOB is more a 'CBP' bit.
    return -1;
  }
  while (1) {
    ++n;
    if (!VP8GetBit(br, p[1])) {
      p = prob[kBands[n]][0];
    } else {  // non zero coeff
      int v;
      if (!VP8GetBit(br, p[2])) {
        p = prob[kBands[n]][1];
        v = 1;
      } else {
        if (!VP8GetBit(br, p[3])) {
          if (!VP8GetBit(br, p[4])) {
            v = 2;
          } else {
            v = 3 + VP8GetBit(br, p[5]);
          }
        } else {
          if (!VP8GetBit(br, p[6])) {
            if (!VP8GetBit(br, p[7])) {
              v = 5 + VP8GetBit(br, 159);
            } else {
              v = 7 + 2 * VP8GetBit(br, 165) + VP8GetBit(br, 145);
            }
          } else {
            const int bit1 = VP8GetBit(br, p[8]);
            const int bit0 = VP8GetBit(br, p[9 + bit1]);
            const int cat = 2 * bit1 + bit0;
            v = 0;
            for (const uint8_t* tab = kCat3456[cat]; *tab; ++tab) {
              v += v + VP8GetBit(br, *tab);
            }
            v += 3 + (8 << cat);
          }
        }
        p = prob[kBands[n]][2];
      }
      const int j = kZigzag[n - 1];
      out[j] = VP8GetSigned(br, v) * dq[j > 0];
      if (n == 16) break;
      if (!VP8GetBit(br, p[0])) {   // EOB
        return n;
      }
    }
  }
  return 15;
}

// Table to unpack four bits into four bytes
static const uint8_t kUnpackTab[16][4] = {
  {0, 0, 0, 0},  {1, 0, 0, 0},  {0, 1, 0, 0},  {1, 1, 0, 0},
  {0, 0, 1, 0},  {1, 0, 1, 0},  {0, 1, 1, 0},  {1, 1, 1, 0},
  {0, 0, 0, 1},  {1, 0, 0, 1},  {0, 1, 0, 1},  {1, 1, 0, 1},
  {0, 0, 1, 1},  {1, 0, 1, 1},  {0, 1, 1, 1},  {1, 1, 1, 1} };

// Macro to pack four LSB of four bytes into four bits.
#define PACK(X, S) \
  ((((*(uint32_t*)(X)) * 0x01020408U) & 0xff000000) >> (S))

typedef const uint8_t (*Proba_t)[NUM_CTX][NUM_PROBAS];  // for const-casting
static int ParseResiduals(VP8Decoder* const dec,
                          VP8MB* const mb, VP8BitReader* const token_br) {
  int out_t_nz, out_l_nz, first;
  Proba_t ac_prob;
  const VP8QuantMatrix* q = &dec->dqm_[dec->segment_];
  int16_t* dst = dec->coeffs_;
  VP8MB* const left_mb = dec->mb_info_ - 1;
  memset(dst, 0, 384 * sizeof(*dst));
  if (!dec->is_i4x4_) {    // parse DC
    int16_t dc[16] = { 0 };
    const int ctx = mb->dc_nz_ + left_mb->dc_nz_;
    const int last = GetCoeffs(token_br, (Proba_t)dec->proba_.coeffs_[1],
                               ctx, q->y2_mat_, 0, dc);
    mb->dc_nz_ = left_mb->dc_nz_ = (last >= 0);
    first = 1;
    ac_prob = (Proba_t)dec->proba_.coeffs_[0];
    VP8TransformWHT(dc, dst);
  } else {
    first = 0;
    ac_prob = (Proba_t)dec->proba_.coeffs_[3];
  }

  uint8_t nz_ac[4], nz_dc[4];
  uint32_t non_zero_ac = 0;
  uint32_t non_zero_dc = 0;

  uint8_t tnz[4], lnz[4];
  memcpy(tnz, kUnpackTab[mb->nz_ & 0xf], sizeof(tnz));
  memcpy(lnz, kUnpackTab[left_mb->nz_ & 0xf], sizeof(lnz));
  for (int y = 0; y < 4; ++y) {
    int l = lnz[y];
    for (int x = 0; x < 4; ++x) {
      const int ctx = l + tnz[x];
      const int last = GetCoeffs(token_br, ac_prob, ctx,
                                 q->y1_mat_, first, dst);
      nz_dc[x] = (dst[0] != 0);
      nz_ac[x] = (last > 0);
      tnz[x] = l = (last >= 0);
      dst += 16;
    }
    lnz[y] = l;
    non_zero_dc |= PACK(nz_dc, 24 - y * 4);
    non_zero_ac |= PACK(nz_ac, 24 - y * 4);
  }
  out_t_nz = PACK(tnz, 24);
  out_l_nz = PACK(lnz, 24);

  memcpy(tnz, kUnpackTab[mb->nz_ >> 4], sizeof(tnz));
  memcpy(lnz, kUnpackTab[left_mb->nz_ >> 4], sizeof(lnz));
  for (int ch = 0; ch < 4; ch += 2) {
    for (int y = 0; y < 2; ++y) {
      int l = lnz[ch + y];
      for (int x = 0; x < 2; ++x) {
        const int ctx = l + tnz[ch + x];
        const int last =
            GetCoeffs(token_br, (Proba_t)dec->proba_.coeffs_[2],
                      ctx, q->uv_mat_, 0, dst);
        nz_dc[y * 2 + x] = (dst[0] != 0);
        nz_ac[y * 2 + x] = (last > 0);
        tnz[ch + x] = l = (last >= 0);
        dst += 16;
      }
      lnz[ch + y] = l;
    }
    non_zero_dc |= PACK(nz_dc, 8 - ch * 2);
    non_zero_ac |= PACK(nz_ac, 8 - ch * 2);
  }
  out_t_nz |= PACK(tnz, 20);
  out_l_nz |= PACK(lnz, 20);
  mb->nz_ = out_t_nz;
  left_mb->nz_ = out_l_nz;

  dec->non_zero_ac_ = non_zero_ac;
  dec->non_zero_ = non_zero_ac | non_zero_dc;
  mb->skip_ = !dec->non_zero_;

  return 1;
}
#undef PACK

//-----------------------------------------------------------------------------
// Main loop

static void SendBlock(VP8Decoder* const dec, VP8Io* io) {
  if (io->put) {
    io->mb_x = dec->mb_x_ * 16;
    io->mb_y = dec->mb_y_ * 16;
    io->mb_w = io->width - io->mb_x;
    io->mb_h = io->height - io->mb_y;
    if (io->mb_w > 16) io->mb_w = 16;
    if (io->mb_h > 16) io->mb_h = 16;
    io->put(io);
  }
}

static int ParseFrame(VP8Decoder* const dec, VP8Io* io) {
  int ok = 1;
  VP8BitReader* const br = &dec->br_;

  for (dec->mb_y_ = 0; dec->mb_y_ < dec->mb_h_; ++dec->mb_y_) {
    memset(dec->intra_l_, B_DC_PRED, sizeof(dec->intra_l_));
    VP8MB* const left = dec->mb_info_ - 1;
    left->nz_ = 0;
    left->dc_nz_ = 0;
    VP8BitReader* token_br = &dec->parts_[dec->mb_y_ & (dec->num_parts_ - 1)];
    for (dec->mb_x_ = 0; dec->mb_x_ < dec->mb_w_;  dec->mb_x_++) {
      VP8MB* const info = dec->mb_info_ + dec->mb_x_;

      // Note: we don't save segment map (yet), as we don't expect
      // to decode more than 1 keyframe.
      if (dec->segment_hdr_.update_map_) {
        // Hardcoded tree parsing
        dec->segment_ = !VP8GetBit(br, dec->proba_.segments_[0]) ?
              VP8GetBit(br, dec->proba_.segments_[1]) :
          2 + VP8GetBit(br, dec->proba_.segments_[2]);
      }
      info->skip_ = dec->use_skip_proba_ ? VP8GetBit(br, dec->skip_p_) : 0;

      VP8ParseIntraMode(br, dec);

      if (!info->skip_) {
        if (!ParseResiduals(dec, info, token_br)) {
          ok = 0;
          break;
        }
      } else {
        left->nz_ = info->nz_ = 0;
        if (!dec->is_i4x4_) {
          left->dc_nz_ = info->dc_nz_ = 0;
        }
        dec->non_zero_ = 0;
        dec->non_zero_ac_ = 0;
      }
      VP8ReconstructBlock(dec);

      // Store filter params
      if (dec->filter_type_ > 0) {
        VP8StoreBlock(dec);
      } else {  // We're done. Send block to user at once.
        SendBlock(dec, io);
      }
    }
    if (!ok) {
      break;
    }
    if (dec->filter_type_ > 0) {   // filter a row
      VP8FilterRow(dec, io);
    }
    if (dec->br_.eof_ || token_br->eof_) {
      ok = 0;
      break;
    }
  }

  // Finish
  if (!dec->update_proba_) {
    dec->proba_ = dec->proba_saved_;
  }
  return ok;
}

// Main entry point
int VP8Decode(VP8Decoder* const dec, VP8Io* const io) {
  if (dec == NULL) {
    return 0;
  }
  if (io == NULL) {
    return VP8SetError(dec, 2, "NULL VP8Io parameter in VP8Decode().");
  }

  if (!dec->ready_) {
    if (!VP8GetHeaders(dec, io)) {
      return 0;
    }
  }
  assert(dec->ready_);

  // will allocate memory and prepare everything.
  if (!VP8InitFrame(dec, io)) {
    VP8Clear(dec);
    return VP8SetError(dec, 3, "Allocation failed");
  }

  // set-up
  if (io->setup) io->setup(io);

  // Main decoding loop
  if (!ParseFrame(dec, io)) {
    VP8Clear(dec);
    return VP8SetError(dec, 3, "Frame decoding failed");
  }

  // tear-down
  if (io->teardown) io->teardown(io);

  dec->ready_ = 0;
  return 1;
}

void VP8Clear(VP8Decoder* const dec) {
  if (dec == NULL) {
    return;
  }
  if (dec->mem_) {
    free(dec->mem_);
  }
  dec->mem_ = NULL;
  dec->mem_size_ = 0;
  memset(&dec->br_, 0, sizeof(dec->br_));
  dec->ready_ = 0;
}