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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This file contains an implementation of an H264 Annex-B video stream parser.
#include <stddef.h>
#include <stdint.h>
#include <sys/types.h>
#include <map>
#include <memory>
#include <vector>
#include "base/macros.h"
#include "base/optional.h"
#include "media/base/media_export.h"
#include "media/base/ranges.h"
#include "media/base/video_codecs.h"
#include "media/base/video_color_space.h"
#include "media/video/h264_bit_reader.h"
namespace gfx {
class Rect;
class Size;
} // namespace gfx
namespace media {
struct SubsampleEntry;
// For explanations of each struct and its members, see H.264 specification
// at
enum Type {
kUnspecified = 0,
kNonIDRSlice = 1,
kSliceDataA = 2,
kSliceDataB = 3,
kSliceDataC = 4,
kIDRSlice = 5,
kSEIMessage = 6,
kSPS = 7,
kPPS = 8,
kAUD = 9,
kEOSeq = 10,
kEOStream = 11,
kFiller = 12,
kSPSExt = 13,
kReserved14 = 14,
kReserved15 = 15,
kReserved16 = 16,
kReserved17 = 17,
kReserved18 = 18,
kCodedSliceAux = 19,
kCodedSliceExtension = 20,
// After (without) start code; we don't own the underlying memory
// and a shallow copy should be made when copying this struct.
const uint8_t* data;
off_t size; // From after start code to start code of next NALU (or EOS).
int nal_ref_idc;
int nal_unit_type;
enum {
kH264ScalingList4x4Length = 16,
kH264ScalingList8x8Length = 64,
enum H264ProfileIDC {
kProfileIDCBaseline = 66,
kProfileIDCConstrainedBaseline = kProfileIDCBaseline,
kProfileIDCMain = 77,
kProfileIDScalableBaseline = 83,
kProfileIDScalableHigh = 86,
kProfileIDCHigh = 100,
kProfileIDHigh10 = 110,
kProfileIDSMultiviewHigh = 118,
kProfileIDHigh422 = 122,
kProfileIDStereoHigh = 128,
kProfileIDHigh444Predictive = 244,
enum AspectRatioIdc {
kExtendedSar = 255,
enum {
// Constants for HRD parameters (spec ch. E.2.2).
kBitRateScaleConstantTerm = 6, // Equation E-37.
kCPBSizeScaleConstantTerm = 4, // Equation E-38.
kDefaultInitialCPBRemovalDelayLength = 24,
kDefaultDPBOutputDelayLength = 24,
kDefaultTimeOffsetLength = 24,
int profile_idc;
bool constraint_set0_flag;
bool constraint_set1_flag;
bool constraint_set2_flag;
bool constraint_set3_flag;
bool constraint_set4_flag;
bool constraint_set5_flag;
int level_idc;
int seq_parameter_set_id;
int chroma_format_idc;
bool separate_colour_plane_flag;
int bit_depth_luma_minus8;
int bit_depth_chroma_minus8;
bool qpprime_y_zero_transform_bypass_flag;
bool seq_scaling_matrix_present_flag;
int scaling_list4x4[6][kH264ScalingList4x4Length];
int scaling_list8x8[6][kH264ScalingList8x8Length];
int log2_max_frame_num_minus4;
int pic_order_cnt_type;
int log2_max_pic_order_cnt_lsb_minus4;
bool delta_pic_order_always_zero_flag;
int offset_for_non_ref_pic;
int offset_for_top_to_bottom_field;
int num_ref_frames_in_pic_order_cnt_cycle;
int expected_delta_per_pic_order_cnt_cycle; // calculated
int offset_for_ref_frame[255];
int max_num_ref_frames;
bool gaps_in_frame_num_value_allowed_flag;
int pic_width_in_mbs_minus1;
int pic_height_in_map_units_minus1;
bool frame_mbs_only_flag;
bool mb_adaptive_frame_field_flag;
bool direct_8x8_inference_flag;
bool frame_cropping_flag;
int frame_crop_left_offset;
int frame_crop_right_offset;
int frame_crop_top_offset;
int frame_crop_bottom_offset;
bool vui_parameters_present_flag;
int sar_width; // Set to 0 when not specified.
int sar_height; // Set to 0 when not specified.
bool bitstream_restriction_flag;
int max_num_reorder_frames;
int max_dec_frame_buffering;
bool timing_info_present_flag;
int num_units_in_tick;
int time_scale;
bool fixed_frame_rate_flag;
bool video_signal_type_present_flag;
int video_format;
bool video_full_range_flag;
bool colour_description_present_flag;
int colour_primaries;
int transfer_characteristics;
int matrix_coefficients;
// TODO(posciak): actually parse these instead of ParseAndIgnoreHRDParameters.
bool nal_hrd_parameters_present_flag;
int cpb_cnt_minus1;
int bit_rate_scale;
int cpb_size_scale;
int bit_rate_value_minus1[32];
int cpb_size_value_minus1[32];
bool cbr_flag[32];
int initial_cpb_removal_delay_length_minus_1;
int cpb_removal_delay_length_minus1;
int dpb_output_delay_length_minus1;
int time_offset_length;
bool low_delay_hrd_flag;
int chroma_array_type;
// Helpers to compute frequently-used values. These methods return
// base::nullopt if they encounter integer overflow. They do not verify that
// the results are in-spec for the given profile or level.
base::Optional<gfx::Size> GetCodedSize() const;
base::Optional<gfx::Rect> GetVisibleRect() const;
VideoColorSpace GetColorSpace() const;
int pic_parameter_set_id;
int seq_parameter_set_id;
bool entropy_coding_mode_flag;
bool bottom_field_pic_order_in_frame_present_flag;
int num_slice_groups_minus1;
// TODO(posciak): Slice groups not implemented, could be added at some point.
int num_ref_idx_l0_default_active_minus1;
int num_ref_idx_l1_default_active_minus1;
bool weighted_pred_flag;
int weighted_bipred_idc;
int pic_init_qp_minus26;
int pic_init_qs_minus26;
int chroma_qp_index_offset;
bool deblocking_filter_control_present_flag;
bool constrained_intra_pred_flag;
bool redundant_pic_cnt_present_flag;
bool transform_8x8_mode_flag;
bool pic_scaling_matrix_present_flag;
int scaling_list4x4[6][kH264ScalingList4x4Length];
int scaling_list8x8[6][kH264ScalingList8x8Length];
int second_chroma_qp_index_offset;
struct MEDIA_EXPORT H264ModificationOfPicNum {
int modification_of_pic_nums_idc;
union {
int abs_diff_pic_num_minus1;
int long_term_pic_num;
struct MEDIA_EXPORT H264WeightingFactors {
bool luma_weight_flag;
bool chroma_weight_flag;
int luma_weight[32];
int luma_offset[32];
int chroma_weight[32][2];
int chroma_offset[32][2];
struct MEDIA_EXPORT H264DecRefPicMarking {
int memory_mgmnt_control_operation;
int difference_of_pic_nums_minus1;
int long_term_pic_num;
int long_term_frame_idx;
int max_long_term_frame_idx_plus1;
struct MEDIA_EXPORT H264SliceHeader {
enum { kRefListSize = 32, kRefListModSize = kRefListSize };
enum Type {
kPSlice = 0,
kBSlice = 1,
kISlice = 2,
kSPSlice = 3,
kSISlice = 4,
bool IsPSlice() const;
bool IsBSlice() const;
bool IsISlice() const;
bool IsSPSlice() const;
bool IsSISlice() const;
bool idr_pic_flag; // from NAL header
int nal_ref_idc; // from NAL header
const uint8_t* nalu_data; // from NAL header
off_t nalu_size; // from NAL header
off_t header_bit_size; // calculated
int first_mb_in_slice;
int slice_type;
int pic_parameter_set_id;
int colour_plane_id; // TODO(posciak): use this!
int frame_num;
bool field_pic_flag;
bool bottom_field_flag;
int idr_pic_id;
int pic_order_cnt_lsb;
int delta_pic_order_cnt_bottom;
int delta_pic_order_cnt0;
int delta_pic_order_cnt1;
int redundant_pic_cnt;
bool direct_spatial_mv_pred_flag;
bool num_ref_idx_active_override_flag;
int num_ref_idx_l0_active_minus1;
int num_ref_idx_l1_active_minus1;
bool ref_pic_list_modification_flag_l0;
bool ref_pic_list_modification_flag_l1;
H264ModificationOfPicNum ref_list_l0_modifications[kRefListModSize];
H264ModificationOfPicNum ref_list_l1_modifications[kRefListModSize];
int luma_log2_weight_denom;
int chroma_log2_weight_denom;
bool luma_weight_l0_flag;
bool chroma_weight_l0_flag;
H264WeightingFactors pred_weight_table_l0;
bool luma_weight_l1_flag;
bool chroma_weight_l1_flag;
H264WeightingFactors pred_weight_table_l1;
bool no_output_of_prior_pics_flag;
bool long_term_reference_flag;
bool adaptive_ref_pic_marking_mode_flag;
H264DecRefPicMarking ref_pic_marking[kRefListSize];
int cabac_init_idc;
int slice_qp_delta;
bool sp_for_switch_flag;
int slice_qs_delta;
int disable_deblocking_filter_idc;
int slice_alpha_c0_offset_div2;
int slice_beta_offset_div2;
// Calculated.
// Size in bits of dec_ref_pic_marking() syntax element.
size_t dec_ref_pic_marking_bit_size;
size_t pic_order_cnt_bit_size;
struct H264SEIRecoveryPoint {
int recovery_frame_cnt;
bool exact_match_flag;
bool broken_link_flag;
int changing_slice_group_idc;
struct MEDIA_EXPORT H264SEIMessage {
enum Type {
kSEIRecoveryPoint = 6,
int type;
int payload_size;
union {
// Placeholder; in future more supported types will contribute to more
// union members here.
H264SEIRecoveryPoint recovery_point;
// Class to parse an Annex-B H.264 stream,
// as specified in chapters 7 and Annex B of the H.264 spec.
class MEDIA_EXPORT H264Parser {
enum Result {
kInvalidStream, // error in stream
kUnsupportedStream, // stream not supported by the parser
kEOStream, // end of stream
// Find offset from start of data to next NALU start code
// and size of found start code (3 or 4 bytes).
// If no start code is found, offset is pointing to the first unprocessed byte
// (i.e. the first byte that was not considered as a possible start of a start
// code) and |*start_code_size| is set to 0.
// Preconditions:
// - |data_size| >= 0
// Postconditions:
// - |*offset| is between 0 and |data_size| included.
// It is strictly less than |data_size| if |data_size| > 0.
// - |*start_code_size| is either 0, 3 or 4.
static bool FindStartCode(const uint8_t* data,
off_t data_size,
off_t* offset,
off_t* start_code_size);
// Wrapper for FindStartCode() that skips over start codes that
// may appear inside of |encrypted_ranges_|.
// Returns true if a start code was found. Otherwise returns false.
static bool FindStartCodeInClearRanges(const uint8_t* data,
off_t data_size,
const Ranges<const uint8_t*>& ranges,
off_t* offset,
off_t* start_code_size);
static VideoCodecProfile ProfileIDCToVideoCodecProfile(int profile_idc);
// Parses the input stream and returns all the NALUs through |nalus|. Returns
// false if the stream is invalid.
static bool ParseNALUs(const uint8_t* stream,
size_t stream_size,
std::vector<H264NALU>* nalus);
void Reset();
// Set current stream pointer to |stream| of |stream_size| in bytes,
// |stream| owned by caller.
// |subsamples| contains information about what parts of |stream| are
// encrypted.
void SetStream(const uint8_t* stream, off_t stream_size);
void SetEncryptedStream(const uint8_t* stream,
off_t stream_size,
const std::vector<SubsampleEntry>& subsamples);
// Read the stream to find the next NALU, identify it and return
// that information in |*nalu|. This advances the stream to the beginning
// of this NALU, but not past it, so subsequent calls to NALU-specific
// parsing functions (ParseSPS, etc.) will parse this NALU.
// If the caller wishes to skip the current NALU, it can call this function
// again, instead of any NALU-type specific parse functions below.
Result AdvanceToNextNALU(H264NALU* nalu);
// NALU-specific parsing functions.
// These should be called after AdvanceToNextNALU().
// SPSes and PPSes are owned by the parser class and the memory for their
// structures is managed here, not by the caller, as they are reused
// across NALUs.
// Parse an SPS/PPS NALU and save their data in the parser, returning id
// of the parsed structure in |*pps_id|/|*sps_id|.
// To get a pointer to a given SPS/PPS structure, use GetSPS()/GetPPS(),
// passing the returned |*sps_id|/|*pps_id| as parameter.
// TODO(posciak,fischman): consider replacing returning Result from Parse*()
// methods with a scoped_ptr and adding an AtEOS() function to check for EOS
// if Parse*() return NULL.
Result ParseSPS(int* sps_id);
Result ParsePPS(int* pps_id);
// Return a pointer to SPS/PPS with given |sps_id|/|pps_id| or NULL if not
// present.
const H264SPS* GetSPS(int sps_id) const;
const H264PPS* GetPPS(int pps_id) const;
// Slice headers and SEI messages are not used across NALUs by the parser
// and can be discarded after current NALU, so the parser does not store
// them, nor does it manage their memory.
// The caller has to provide and manage it instead.
// Parse a slice header, returning it in |*shdr|. |*nalu| must be set to
// the NALU returned from AdvanceToNextNALU() and corresponding to |*shdr|.
Result ParseSliceHeader(const H264NALU& nalu, H264SliceHeader* shdr);
// Parse a SEI message, returning it in |*sei_msg|, provided and managed
// by the caller.
Result ParseSEI(H264SEIMessage* sei_msg);
// Move the stream pointer to the beginning of the next NALU,
// i.e. pointing at the next start code.
// Return true if a NALU has been found.
// If a NALU is found:
// - its size in bytes is returned in |*nalu_size| and includes
// the start code as well as the trailing zero bits.
// - the size in bytes of the start code is returned in |*start_code_size|.
bool LocateNALU(off_t* nalu_size, off_t* start_code_size);
// Exp-Golomb code parsing as specified in chapter 9.1 of the spec.
// Read one unsigned exp-Golomb code from the stream and return in |*val|.
Result ReadUE(int* val);
// Read one signed exp-Golomb code from the stream and return in |*val|.
Result ReadSE(int* val);
// Parse scaling lists (see spec).
Result ParseScalingList(int size, int* scaling_list, bool* use_default);
Result ParseSPSScalingLists(H264SPS* sps);
Result ParsePPSScalingLists(const H264SPS& sps, H264PPS* pps);
// Parse optional VUI parameters in SPS (see spec).
Result ParseVUIParameters(H264SPS* sps);
// Set |hrd_parameters_present| to true only if they are present.
Result ParseAndIgnoreHRDParameters(bool* hrd_parameters_present);
// Parse reference picture lists' modifications (see spec).
Result ParseRefPicListModifications(H264SliceHeader* shdr);
Result ParseRefPicListModification(int num_ref_idx_active_minus1,
H264ModificationOfPicNum* ref_list_mods);
// Parse prediction weight table (see spec).
Result ParsePredWeightTable(const H264SPS& sps, H264SliceHeader* shdr);
// Parse weighting factors (see spec).
Result ParseWeightingFactors(int num_ref_idx_active_minus1,
int chroma_array_type,
int luma_log2_weight_denom,
int chroma_log2_weight_denom,
H264WeightingFactors* w_facts);
// Parse decoded reference picture marking information (see spec).
Result ParseDecRefPicMarking(H264SliceHeader* shdr);
// Pointer to the current NALU in the stream.
const uint8_t* stream_;
// Bytes left in the stream after the current NALU.
off_t bytes_left_;
H264BitReader br_;
// PPSes and SPSes stored for future reference.
std::map<int, std::unique_ptr<H264SPS>> active_SPSes_;
std::map<int, std::unique_ptr<H264PPS>> active_PPSes_;
// Ranges of encrypted bytes in the buffer passed to
// SetEncryptedStream().
Ranges<const uint8_t*> encrypted_ranges_;
} // namespace media
#endif // MEDIA_VIDEO_H264_PARSER_H_