diff options
Diffstat (limited to 'media/libaom/src/tools/obu_parser.cc')
| -rw-r--r-- | media/libaom/src/tools/obu_parser.cc | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/media/libaom/src/tools/obu_parser.cc b/media/libaom/src/tools/obu_parser.cc new file mode 100644 index 000000000..7d71386ce --- /dev/null +++ b/media/libaom/src/tools/obu_parser.cc @@ -0,0 +1,190 @@ +/* + * 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 <string.h> + +#include <cstdio> +#include <string> + +#include "aom/aom_codec.h" +#include "aom/aom_integer.h" +#include "aom_ports/mem_ops.h" +#include "av1/common/obu_util.h" +#include "tools/obu_parser.h" + +namespace aom_tools { + +// Basic OBU syntax +// 8 bits: Header +// 7 +// forbidden bit +// 6,5,4,3 +// type bits +// 2 +// extension flag bit +// 1 +// has size field bit +// 0 +// reserved bit +const uint32_t kObuForbiddenBitMask = 0x1; +const uint32_t kObuForbiddenBitShift = 7; +const uint32_t kObuTypeBitsMask = 0xF; +const uint32_t kObuTypeBitsShift = 3; +const uint32_t kObuExtensionFlagBitMask = 0x1; +const uint32_t kObuExtensionFlagBitShift = 2; +const uint32_t kObuHasSizeFieldBitMask = 0x1; +const uint32_t kObuHasSizeFieldBitShift = 1; + +// When extension flag bit is set: +// 8 bits: extension header +// 7,6,5 +// temporal ID +// 4,3 +// spatial ID +// 2,1,0 +// reserved bits +const uint32_t kObuExtTemporalIdBitsMask = 0x7; +const uint32_t kObuExtTemporalIdBitsShift = 5; +const uint32_t kObuExtSpatialIdBitsMask = 0x3; +const uint32_t kObuExtSpatialIdBitsShift = 3; + +bool ValidObuType(int obu_type) { + switch (obu_type) { + case OBU_SEQUENCE_HEADER: + case OBU_TEMPORAL_DELIMITER: + case OBU_FRAME_HEADER: + case OBU_TILE_GROUP: + case OBU_METADATA: + case OBU_FRAME: + case OBU_REDUNDANT_FRAME_HEADER: + case OBU_TILE_LIST: + case OBU_PADDING: return true; + } + return false; +} + +bool ParseObuHeader(uint8_t obu_header_byte, ObuHeader *obu_header) { + const int forbidden_bit = + (obu_header_byte >> kObuForbiddenBitShift) & kObuForbiddenBitMask; + if (forbidden_bit) { + fprintf(stderr, "Invalid OBU, forbidden bit set.\n"); + return false; + } + + obu_header->type = static_cast<OBU_TYPE>( + (obu_header_byte >> kObuTypeBitsShift) & kObuTypeBitsMask); + if (!ValidObuType(obu_header->type)) { + fprintf(stderr, "Invalid OBU type: %d.\n", obu_header->type); + return false; + } + + obu_header->has_extension = + (obu_header_byte >> kObuExtensionFlagBitShift) & kObuExtensionFlagBitMask; + obu_header->has_size_field = + (obu_header_byte >> kObuHasSizeFieldBitShift) & kObuHasSizeFieldBitMask; + return true; +} + +bool ParseObuExtensionHeader(uint8_t ext_header_byte, ObuHeader *obu_header) { + obu_header->temporal_layer_id = + (ext_header_byte >> kObuExtTemporalIdBitsShift) & + kObuExtTemporalIdBitsMask; + obu_header->spatial_layer_id = + (ext_header_byte >> kObuExtSpatialIdBitsShift) & kObuExtSpatialIdBitsMask; + + return true; +} + +void PrintObuHeader(const ObuHeader *header) { + printf( + " OBU type: %s\n" + " extension: %s\n", + aom_obu_type_to_string(static_cast<OBU_TYPE>(header->type)), + header->has_extension ? "yes" : "no"); + if (header->has_extension) { + printf( + " temporal_id: %d\n" + " spatial_id: %d\n", + header->temporal_layer_id, header->temporal_layer_id); + } +} + +bool DumpObu(const uint8_t *data, int length, int *obu_overhead_bytes) { + const int kObuHeaderSizeBytes = 1; + const int kMinimumBytesRequired = 1 + kObuHeaderSizeBytes; + int consumed = 0; + int obu_overhead = 0; + ObuHeader obu_header; + while (consumed < length) { + const int remaining = length - consumed; + if (remaining < kMinimumBytesRequired) { + fprintf(stderr, + "OBU parse error. Did not consume all data, %d bytes remain.\n", + remaining); + return false; + } + + int obu_header_size = 0; + + memset(&obu_header, 0, sizeof(obu_header)); + const uint8_t obu_header_byte = *(data + consumed); + if (!ParseObuHeader(obu_header_byte, &obu_header)) { + fprintf(stderr, "OBU parsing failed at offset %d.\n", consumed); + return false; + } + + ++obu_overhead; + ++obu_header_size; + + if (obu_header.has_extension) { + const uint8_t obu_ext_header_byte = + *(data + consumed + kObuHeaderSizeBytes); + if (!ParseObuExtensionHeader(obu_ext_header_byte, &obu_header)) { + fprintf(stderr, "OBU extension parsing failed at offset %d.\n", + consumed + kObuHeaderSizeBytes); + return false; + } + + ++obu_overhead; + ++obu_header_size; + } + + PrintObuHeader(&obu_header); + + uint64_t obu_size = 0; + size_t length_field_size = 0; + if (aom_uleb_decode(data + consumed + obu_header_size, + remaining - obu_header_size, &obu_size, + &length_field_size) != 0) { + fprintf(stderr, "OBU size parsing failed at offset %d.\n", + consumed + obu_header_size); + return false; + } + int current_obu_length = static_cast<int>(obu_size); + if (obu_header_size + static_cast<int>(length_field_size) + + current_obu_length > + remaining) { + fprintf(stderr, "OBU parsing failed: not enough OBU data.\n"); + return false; + } + consumed += obu_header_size + static_cast<int>(length_field_size) + + current_obu_length; + printf(" length: %d\n", + static_cast<int>(obu_header_size + length_field_size + + current_obu_length)); + } + + if (obu_overhead_bytes != nullptr) *obu_overhead_bytes = obu_overhead; + printf(" TU size: %d\n", consumed); + + return true; +} + +} // namespace aom_tools |