av1/decoder/obu.c

/*
 * Copyright (c) 2017, Alliance for Open Media. All rights reserved
 *
 * This source code is subject to the terms of the BSD 2 Clause License and
 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
 * was not distributed with this source code in the LICENSE file, you can
 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
 * Media Patent License 1.0 was not distributed with this source code in the
 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 */

#include <assert.h>

#include "./aom_config.h"

#include "aom/aom_codec.h"
#include "aom_dsp/bitreader_buffer.h"
#include "aom_ports/mem_ops.h"

#include "av1/common/common.h"
#include "av1/decoder/decoder.h"
#include "av1/decoder/decodeframe.h"
#include "av1/decoder/obu.h"

// Picture prediction structures (0-12 are predefined) in scalability metadata.
typedef enum {
  SCALABILITY_L1T2 = 0,
  SCALABILITY_L1T3 = 1,
  SCALABILITY_L2T1 = 2,
  SCALABILITY_L2T2 = 3,
  SCALABILITY_L2T3 = 4,
  SCALABILITY_S2T1 = 5,
  SCALABILITY_S2T2 = 6,
  SCALABILITY_S2T3 = 7,
  SCALABILITY_L2T2h = 8,
  SCALABILITY_L2T3h = 9,
  SCALABILITY_S2T1h = 10,
  SCALABILITY_S2T2h = 11,
  SCALABILITY_S2T3h = 12,
  SCALABILITY_SS = 13
} SCALABILITY_STRUCTURES;

int get_obu_type(uint8_t obu_header, OBU_TYPE *obu_type) {
  if (!obu_type) return -1;
  *obu_type = (OBU_TYPE)((obu_header >> 3) & 0xF);
  switch (*obu_type) {
    case OBU_SEQUENCE_HEADER:
    case OBU_TEMPORAL_DELIMITER:
    case OBU_FRAME_HEADER:
    case OBU_REDUNDANT_FRAME_HEADER:
    case OBU_FRAME:
    case OBU_TILE_GROUP:
    case OBU_METADATA:
    case OBU_PADDING: break;
    default: return -1;
  }
  return 0;
}

// Returns 1 when OBU type is valid, and 0 otherwise.
static int valid_obu_type(int obu_type) {
  int valid_type = 0;
  switch (obu_type) {
    case OBU_SEQUENCE_HEADER:
    case OBU_TEMPORAL_DELIMITER:
    case OBU_FRAME_HEADER:
    case OBU_REDUNDANT_FRAME_HEADER:
    case OBU_FRAME:
    case OBU_TILE_GROUP:
    case OBU_METADATA:
    case OBU_PADDING: valid_type = 1; break;
    default: break;
  }
  return valid_type;
}

// Parses OBU header and stores values in 'header'.
static aom_codec_err_t read_obu_header(struct aom_read_bit_buffer *rb,
                                       int is_annexb, ObuHeader *header) {
  if (!rb || !header) return AOM_CODEC_INVALID_PARAM;

  header->size = 1;

  // first bit is obu_forbidden_bit (0) according to R19
  aom_rb_read_bit(rb);

  header->type = (OBU_TYPE)aom_rb_read_literal(rb, 4);

  if (!valid_obu_type(header->type)) return AOM_CODEC_CORRUPT_FRAME;

  header->has_extension = aom_rb_read_bit(rb);
  header->has_length_field = aom_rb_read_bit(rb);

  if (!header->has_length_field && !is_annexb) {
    // section 5 obu streams must have length field set.
    return AOM_CODEC_UNSUP_BITSTREAM;
  }

  aom_rb_read_bit(rb);  // reserved

  const ptrdiff_t bit_buffer_byte_length = rb->bit_buffer_end - rb->bit_buffer;
  if (header->has_extension && bit_buffer_byte_length > 1) {
    header->size += 1;
    header->temporal_layer_id = aom_rb_read_literal(rb, 3);
    header->enhancement_layer_id = aom_rb_read_literal(rb, 2);
    aom_rb_read_literal(rb, 3);  // reserved
  }

  return AOM_CODEC_OK;
}

aom_codec_err_t aom_read_obu_header(uint8_t *buffer, size_t buffer_length,
                                    size_t *consumed, ObuHeader *header,
                                    int is_annexb) {
  if (buffer_length < 1 || !consumed || !header) return AOM_CODEC_INVALID_PARAM;

  // TODO(tomfinegan): Set the error handler here and throughout this file, and
  // confirm parsing work done via aom_read_bit_buffer is successful.
  struct aom_read_bit_buffer rb = { buffer, buffer + buffer_length, 0, NULL,
                                    NULL };
  aom_codec_err_t parse_result = read_obu_header(&rb, is_annexb, header);
  if (parse_result == AOM_CODEC_OK) *consumed = header->size;
  return parse_result;
}

static int is_obu_in_current_operating_point(AV1Decoder *pbi,
                                             ObuHeader obu_header) {
  if (!pbi->current_operating_point) {
    return 1;
  }

  if ((pbi->current_operating_point >> obu_header.temporal_layer_id) & 0x1 &&
      (pbi->current_operating_point >> (obu_header.enhancement_layer_id + 8)) &
          0x1) {
    return 1;
  }
  return 0;
}

static uint32_t read_temporal_delimiter_obu() { return 0; }

static uint32_t read_sequence_header_obu(AV1Decoder *pbi,
                                         struct aom_read_bit_buffer *rb) {
  AV1_COMMON *const cm = &pbi->common;
  uint32_t saved_bit_offset = rb->bit_offset;

  cm->profile = av1_read_profile(rb);

  SequenceHeader *seq_params = &cm->seq_params;

  // Still picture or not
  seq_params->still_picture = aom_rb_read_bit(rb);

  uint8_t operating_points_minus1_cnt = aom_rb_read_literal(rb, 5);
  pbi->common.enhancement_layers_cnt = operating_points_minus1_cnt + 1;
  int i;
  for (i = 0; i < operating_points_minus1_cnt + 1; i++) {
    seq_params->operating_point_idc[i] = aom_rb_read_literal(rb, 12);
    seq_params->level[i] = aom_rb_read_literal(rb, 4);
    seq_params->decoder_rate_model_param_present_flag[i] =
        aom_rb_read_literal(rb, 1);
    if (seq_params->decoder_rate_model_param_present_flag[i]) {
      seq_params->decode_to_display_rate_ratio[i] = aom_rb_read_literal(rb, 12);
      seq_params->initial_display_delay[i] = aom_rb_read_literal(rb, 24);
      seq_params->extra_frame_buffers[i] = aom_rb_read_literal(rb, 4);
    }
  }
  // This decoder supports all levels.  Choose the first operating point
  pbi->current_operating_point = seq_params->operating_point_idc[0];

  read_sequence_header(cm, rb);

  av1_read_bitdepth_colorspace_sampling(cm, rb, pbi->allow_lowbitdepth);

  av1_read_timing_info_header(cm, rb);

  cm->film_grain_params_present = aom_rb_read_bit(rb);

  av1_check_trailing_bits(pbi, rb);

  pbi->sequence_header_ready = 1;

  return ((rb->bit_offset - saved_bit_offset + 7) >> 3);
}

static uint32_t read_frame_header_obu(AV1Decoder *pbi,
                                      struct aom_read_bit_buffer *rb,
                                      const uint8_t *data,
                                      const uint8_t **p_data_end) {
  av1_decode_frame_headers_and_setup(pbi, rb, data, p_data_end);
  return (uint32_t)(pbi->uncomp_hdr_size);
}

static uint32_t read_tile_group_header(AV1Decoder *pbi,
                                       struct aom_read_bit_buffer *rb,
                                       int *startTile, int *endTile) {
  AV1_COMMON *const cm = &pbi->common;
  uint32_t saved_bit_offset = rb->bit_offset;
  int tile_start_and_end_present_flag = 0;
  const int num_tiles = pbi->common.tile_rows * pbi->common.tile_cols;

  if (!pbi->common.large_scale_tile && num_tiles > 1) {
    tile_start_and_end_present_flag = aom_rb_read_bit(rb);
  }
  if (pbi->common.large_scale_tile || num_tiles == 1 ||
      !tile_start_and_end_present_flag) {
    *startTile = 0;
    *endTile = num_tiles - 1;
    return ((rb->bit_offset - saved_bit_offset + 7) >> 3);
  }

  *startTile = aom_rb_read_literal(rb, cm->log2_tile_rows + cm->log2_tile_cols);
  *endTile = aom_rb_read_literal(rb, cm->log2_tile_rows + cm->log2_tile_cols);

  return ((rb->bit_offset - saved_bit_offset + 7) >> 3);
}

static uint32_t read_one_tile_group_obu(AV1Decoder *pbi,
                                        struct aom_read_bit_buffer *rb,
                                        int is_first_tg, const uint8_t *data,
                                        const uint8_t *data_end,
                                        const uint8_t **p_data_end,
                                        int *is_last_tg) {
  AV1_COMMON *const cm = &pbi->common;
  int startTile, endTile;
  uint32_t header_size, tg_payload_size;

  header_size = read_tile_group_header(pbi, rb, &startTile, &endTile);
  if (startTile > endTile) return header_size;
  data += header_size;
  av1_decode_tg_tiles_and_wrapup(pbi, data, data_end, p_data_end, startTile,
                                 endTile, is_first_tg);

  tg_payload_size = (uint32_t)(*p_data_end - data);

  // TODO(shan):  For now, assume all tile groups received in order
  *is_last_tg = endTile == cm->tile_rows * cm->tile_cols - 1;
  return header_size + tg_payload_size;
}

static void read_metadata_private_data(const uint8_t *data, size_t sz) {
  for (size_t i = 0; i < sz; i++) {
    mem_get_le16(data);
    data += 2;
  }
}

static void read_metadata_hdr_cll(const uint8_t *data) {
  mem_get_le16(data);
  mem_get_le16(data + 2);
}

static void read_metadata_hdr_mdcv(const uint8_t *data) {
  for (int i = 0; i < 3; i++) {
    mem_get_le16(data);
    data += 2;
    mem_get_le16(data);
    data += 2;
  }

  mem_get_le16(data);
  data += 2;
  mem_get_le16(data);
  data += 2;
  mem_get_le16(data);
  data += 2;
  mem_get_le16(data);
}

static void scalability_structure(struct aom_read_bit_buffer *rb) {
  int enhancement_layers_cnt = aom_rb_read_literal(rb, 2);
  int enhancement_layer_dimensions_present_flag = aom_rb_read_literal(rb, 1);
  int enhancement_layer_description_present_flag = aom_rb_read_literal(rb, 1);
  int temporal_group_description_flag = aom_rb_read_literal(rb, 1);
  aom_rb_read_literal(rb, 3);  // reserved

  if (enhancement_layer_dimensions_present_flag) {
    int i;
    for (i = 0; i < enhancement_layers_cnt + 1; i++) {
      aom_rb_read_literal(rb, 16);
      aom_rb_read_literal(rb, 16);
    }
  }
  if (enhancement_layer_description_present_flag) {
    int i;
    for (i = 0; i < enhancement_layers_cnt + 1; i++) {
      aom_rb_read_literal(rb, 8);
    }
  }
  if (temporal_group_description_flag) {
    int i, j, temporal_group_size;
    temporal_group_size = aom_rb_read_literal(rb, 8);
    for (i = 0; i < temporal_group_size; i++) {
      aom_rb_read_literal(rb, 3);
      aom_rb_read_literal(rb, 1);
      int temporal_group_ref_cnt = aom_rb_read_literal(rb, 2);
      aom_rb_read_literal(rb, 2);
      for (j = 0; j < temporal_group_ref_cnt; j++) {
        aom_rb_read_literal(rb, 8);
      }
    }
  }
}

static void read_metadata_scalability(const uint8_t *data, size_t sz) {
  struct aom_read_bit_buffer rb = { data, data + sz, 0, NULL, NULL };
  int scalability_mode_idc = aom_rb_read_literal(&rb, 8);
  if (scalability_mode_idc == SCALABILITY_SS) {
    scalability_structure(&rb);
  }
}

static size_t read_metadata(const uint8_t *data, size_t sz) {
  if (sz < 2) return sz;  // Invalid data size.
  const OBU_METADATA_TYPE metadata_type = (OBU_METADATA_TYPE)mem_get_le16(data);

  if (metadata_type == OBU_METADATA_TYPE_PRIVATE_DATA) {
    read_metadata_private_data(data + 2, sz - 2);
  } else if (metadata_type == OBU_METADATA_TYPE_HDR_CLL) {
    read_metadata_hdr_cll(data + 2);
  } else if (metadata_type == OBU_METADATA_TYPE_HDR_MDCV) {
    read_metadata_hdr_mdcv(data + 2);
  } else if (metadata_type == OBU_METADATA_TYPE_SCALABILITY) {
    read_metadata_scalability(data + 2, sz - 2);
  }

  return sz;
}

static aom_codec_err_t read_obu_size(const uint8_t *data,
                                     size_t bytes_available,
                                     size_t *const obu_size,
                                     size_t *const length_field_size) {
  uint64_t u_obu_size = 0;
  if (aom_uleb_decode(data, bytes_available, &u_obu_size, length_field_size) !=
      0) {
    return AOM_CODEC_CORRUPT_FRAME;
  }

  *obu_size = (size_t)u_obu_size;
  return AOM_CODEC_OK;
}

void av1_decode_frame_from_obus(struct AV1Decoder *pbi, const uint8_t *data,
                                const uint8_t *data_end,
                                const uint8_t **p_data_end) {
  AV1_COMMON *const cm = &pbi->common;
  int frame_decoding_finished = 0;
  int is_first_tg_obu_received = 1;
  int frame_header_received = 0;
  int frame_header_size = 0;
  int seq_header_received = 0;
  size_t seq_header_size = 0;
  ObuHeader obu_header;
  memset(&obu_header, 0, sizeof(obu_header));

  if (data_end < data) {
    cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
    return;
  }

  // decode frame as a series of OBUs
  while (!frame_decoding_finished && !cm->error.error_code) {
    struct aom_read_bit_buffer rb;
    size_t payload_size = 0;
    size_t decoded_payload_size = 0;
    size_t obu_payload_offset = 0;
    const size_t bytes_available = data_end - data;

    if (bytes_available < 1) {
      cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
      return;
    }

    size_t length_field_size = 0;
    size_t obu_size = 0;
    if (cm->is_annexb) {
      if (read_obu_size(data, bytes_available, &obu_size, &length_field_size) !=
          AOM_CODEC_OK) {
        cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
        return;
      }
    }
    if (data_end < data + length_field_size) {
      cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
      return;
    }
    av1_init_read_bit_buffer(pbi, &rb, data + length_field_size, data_end);

    const aom_codec_err_t status =
        read_obu_header(&rb, cm->is_annexb, &obu_header);
    if (status != AOM_CODEC_OK) {
      cm->error.error_code = status;
      return;
    }

    if (!cm->is_annexb) {
      if (read_obu_size(data + obu_header.size,
                        bytes_available - obu_header.size, &payload_size,
                        &length_field_size) != AOM_CODEC_OK) {
        cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
        return;
      }
      av1_init_read_bit_buffer(
          pbi, &rb, data + length_field_size + obu_header.size, data_end);
    } else {
      payload_size = obu_size - obu_header.size;
    }

    data += length_field_size + obu_header.size;
    if (data_end < data) {
      cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
      return;
    }

    cm->temporal_layer_id = obu_header.temporal_layer_id;
    cm->enhancement_layer_id = obu_header.enhancement_layer_id;

    switch (obu_header.type) {
      case OBU_TEMPORAL_DELIMITER:
        decoded_payload_size = read_temporal_delimiter_obu();
        break;
      case OBU_SEQUENCE_HEADER:
        if (!seq_header_received) {
          decoded_payload_size = read_sequence_header_obu(pbi, &rb);
          seq_header_size = decoded_payload_size;
          seq_header_received = 1;
        } else {
          // Seeing another sequence header, skip as all sequence headers
          // are requred to be identical.
          if (payload_size != seq_header_size) {
            cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
            return;
          }
          decoded_payload_size = seq_header_size;
        }
        break;
      case OBU_FRAME_HEADER:
      case OBU_REDUNDANT_FRAME_HEADER:
      case OBU_FRAME:
        // don't decode obu if it's not in current operating mode
        if (!is_obu_in_current_operating_point(pbi, obu_header)) {
          decoded_payload_size = payload_size;
          break;
        }
        // Only decode first frame header received
        if (!frame_header_received) {
          av1_init_read_bit_buffer(pbi, &rb, data, data_end);
          frame_header_size = read_frame_header_obu(pbi, &rb, data, p_data_end);
          frame_header_received = 1;
        }
        decoded_payload_size = frame_header_size;
        if (cm->show_existing_frame) {
          frame_decoding_finished = 1;
          break;
        }
        if (obu_header.type != OBU_FRAME) break;
        obu_payload_offset = frame_header_size;
        AOM_FALLTHROUGH_INTENDED;  // fall through to read tile group.
      case OBU_TILE_GROUP:
        if (!frame_header_received) {
          cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
          return;
        }
        if (data_end < data + obu_payload_offset ||
            data_end < data + payload_size) {
          cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
          return;
        }
        // don't decode obu if it's not in current operating mode
        if (!is_obu_in_current_operating_point(pbi, obu_header)) {
          decoded_payload_size = payload_size;
          break;
        }
        decoded_payload_size += read_one_tile_group_obu(
            pbi, &rb, is_first_tg_obu_received, data + obu_payload_offset,
            data + payload_size, p_data_end, &frame_decoding_finished);
        is_first_tg_obu_received = 0;
        break;
      case OBU_METADATA:
        // don't decode obu if it's not in current operating mode
        if (!is_obu_in_current_operating_point(pbi, obu_header)) {
          decoded_payload_size = payload_size;
          break;
        }
        decoded_payload_size = read_metadata(data, payload_size);
        break;
      case OBU_PADDING:
      default:
        // Skip unrecognized OBUs
        decoded_payload_size = payload_size;
        break;
    }

    // Check that the signalled OBU size matches the actual amount of data read
    if (decoded_payload_size > payload_size) {
      cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
      return;
    }

    // If there are extra padding bytes, they should all be zero
    while (decoded_payload_size < payload_size) {
      uint8_t padding_byte = data[decoded_payload_size++];
      if (padding_byte != 0) {
        cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
        return;
      }
    }

    data += payload_size;
    if (data_end < data) {
      cm->error.error_code = AOM_CODEC_CORRUPT_FRAME;
      return;
    }
  }
}