/*
* Copyright (c) 2021, Hunter Salyer <thefalsehonesty@gmail.com>
* Copyright (c) 2022-2023, Gregory Bertilson <Zaggy1024@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Debug.h>
#include <AK/Function.h>
#include <AK/Math.h>
#include <AK/Optional.h>
#include <AK/Time.h>
#include <AK/Utf8View.h>
#include <LibCore/MappedFile.h>
#include "Reader.h"
namespace Media::Matroska {
#define TRY_READ(expression) DECODER_TRY(DecoderErrorCategory::Corrupted, expression)
// RFC 8794 - Extensible Binary Meta Language
// https://datatracker.ietf.org/doc/html/rfc8794
constexpr u32 EBML_MASTER_ELEMENT_ID = 0x1A45DFA3;
constexpr u32 EBML_CRC32_ELEMENT_ID = 0xBF;
constexpr u32 EBML_VOID_ELEMENT_ID = 0xEC;
// Matroska elements' IDs and types are listed at this URL:
// https://www.matroska.org/technical/elements.html
constexpr u32 SEGMENT_ELEMENT_ID = 0x18538067;
constexpr u32 DOCTYPE_ELEMENT_ID = 0x4282;
constexpr u32 DOCTYPE_VERSION_ELEMENT_ID = 0x4287;
constexpr u32 SEEK_HEAD_ELEMENT_ID = 0x114D9B74;
constexpr u32 SEEK_ELEMENT_ID = 0x4DBB;
constexpr u32 SEEK_ID_ELEMENT_ID = 0x53AB;
constexpr u32 SEEK_POSITION_ELEMENT_ID = 0x53AC;
constexpr u32 SEGMENT_INFORMATION_ELEMENT_ID = 0x1549A966;
constexpr u32 TRACK_ELEMENT_ID = 0x1654AE6B;
constexpr u32 CLUSTER_ELEMENT_ID = 0x1F43B675;
constexpr u32 TIMESTAMP_SCALE_ID = 0x2AD7B1;
constexpr u32 MUXING_APP_ID = 0x4D80;
constexpr u32 WRITING_APP_ID = 0x5741;
constexpr u32 DURATION_ID = 0x4489;
// Tracks
constexpr u32 TRACK_ENTRY_ID = 0xAE;
constexpr u32 TRACK_NUMBER_ID = 0xD7;
constexpr u32 TRACK_UID_ID = 0x73C5;
constexpr u32 TRACK_TYPE_ID = 0x83;
constexpr u32 TRACK_LANGUAGE_ID = 0x22B59C;
constexpr u32 TRACK_CODEC_ID = 0x86;
constexpr u32 TRACK_CODEC_PRIVATE = 0x63A2;
constexpr u32 TRACK_TIMESTAMP_SCALE_ID = 0x23314F;
constexpr u32 TRACK_OFFSET_ID = 0x537F;
constexpr u32 TRACK_VIDEO_ID = 0xE0;
constexpr u32 TRACK_AUDIO_ID = 0xE1;
// Video
constexpr u32 PIXEL_WIDTH_ID = 0xB0;
constexpr u32 PIXEL_HEIGHT_ID = 0xBA;
constexpr u32 COLOR_ENTRY_ID = 0x55B0;
constexpr u32 PRIMARIES_ID = 0x55BB;
constexpr u32 TRANSFER_CHARACTERISTICS_ID = 0x55BA;
constexpr u32 MATRIX_COEFFICIENTS_ID = 0x55B1;
constexpr u32 RANGE_ID = 0x55B9;
constexpr u32 BITS_PER_CHANNEL_ID = 0x55B2;
// Audio
constexpr u32 CHANNELS_ID = 0x9F;
constexpr u32 BIT_DEPTH_ID = 0x6264;
// Clusters
constexpr u32 SIMPLE_BLOCK_ID = 0xA3;
constexpr u32 TIMESTAMP_ID = 0xE7;
// Cues
constexpr u32 CUES_ID = 0x1C53BB6B;
constexpr u32 CUE_POINT_ID = 0xBB;
constexpr u32 CUE_TIME_ID = 0xB3;
constexpr u32 CUE_TRACK_POSITIONS_ID = 0xB7;
constexpr u32 CUE_TRACK_ID = 0xF7;
constexpr u32 CUE_CLUSTER_POSITION_ID = 0xF1;
constexpr u32 CUE_RELATIVE_POSITION_ID = 0xF0;
constexpr u32 CUE_CODEC_STATE_ID = 0xEA;
constexpr u32 CUE_REFERENCE_ID = 0xDB;
DecoderErrorOr<Reader> Reader::from_file(StringView path)
{
auto mapped_file = DECODER_TRY(DecoderErrorCategory::IO, Core::MappedFile::map(path));
return from_mapped_file(move(mapped_file));
}
DecoderErrorOr<Reader> Reader::from_mapped_file(NonnullOwnPtr<Core::MappedFile> mapped_file)
{
auto reader = TRY(from_data(mapped_file->bytes()));
reader.m_mapped_file = make_ref_counted<Core::SharedMappedFile>(move(mapped_file));
return reader;
}
DecoderErrorOr<Reader> Reader::from_data(ReadonlyBytes data)
{
Reader reader(data);
TRY(reader.parse_initial_data());
return reader;
}
// Returns the position of the first element that is read from this master element.
static DecoderErrorOr<size_t> parse_master_element(Streamer& streamer, [[maybe_unused]] StringView element_name, Function<DecoderErrorOr<IterationDecision>(u64)> element_consumer)
{
auto element_data_size = TRY_READ(streamer.read_variable_size_integer());
dbgln_if(MATROSKA_DEBUG, "{} has {} octets of data.", element_name, element_data_size);
bool first_element = true;
auto first_element_position = streamer.position();
streamer.push_octets_read();
while (streamer.octets_read() < element_data_size) {
dbgln_if(MATROSKA_TRACE_DEBUG, "====== Reading element ======");
auto element_id = TRY_READ(streamer.read_variable_size_integer(false));
dbgln_if(MATROSKA_TRACE_DEBUG, "{:s} element ID is {:#010x}", element_name, element_id);
if (element_id == EBML_CRC32_ELEMENT_ID) {
// The CRC-32 Element contains a 32-bit Cyclic Redundancy Check value of all the
// Element Data of the Parent Element as stored except for the CRC-32 Element itself.
// When the CRC-32 Element is present, the CRC-32 Element MUST be the first ordered
// EBML Element within its Parent Element for easier reading.
if (!first_element)
return DecoderError::corrupted("CRC32 element must be the first child"sv);
// All Top-Level Elements of an EBML Document that are Master Elements SHOULD include a
// CRC-32 Element as a Child Element. The CRC in use is the IEEE-CRC-32 algorithm as used
// in the [ISO3309] standard and in Section 8.1.1.6.2 of [ITU.V42], with initial value of
// 0xFFFFFFFF. The CRC value MUST be computed on a little-endian bytestream and MUST use
// little-endian storage.
// FIXME: Currently we skip the CRC-32 Element instead of checking it. It may be worth
// verifying the contents of the SeekHead, Segment Info, and Tracks Elements.
// Note that Cluster Elements tend to be quite large, so verifying their integrity
// will result in longer buffering times in streamed contexts, so it may not be
// worth the effort checking those. It would also prevent error correction in
// video codecs from taking effect.
TRY_READ(streamer.read_unknown_element());
continue;
}
if (element_id == EBML_VOID_ELEMENT_ID) {
// Used to void data or to avoid unexpected behaviors when using damaged data.
// The content is discarded. Also used to reserve space in a subelement for later use.
TRY_READ(streamer.read_unknown_element());
continue;
}
auto result = element_consumer(element_id);
if (result.is_error())
return DecoderError::format(result.error().category(), "{} -> {}", element_name, result.error().description());
if (result.release_value() == IterationDecision::Break)
break;
dbgln_if(MATROSKA_TRACE_DEBUG, "Read {} octets of the {} so far.", streamer.octets_read(), element_name);
first_element = false;
}
streamer.pop_octets_read();
return first_element_position;
}
static DecoderErrorOr<EBMLHeader> parse_ebml_header(Streamer& streamer)
{
EBMLHeader header;
TRY(parse_master_element(streamer, "Header"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case DOCTYPE_ELEMENT_ID:
header.doc_type = TRY_READ(streamer.read_string());
dbgln_if(MATROSKA_DEBUG, "Read DocType attribute: {}", header.doc_type);
break;
case DOCTYPE_VERSION_ELEMENT_ID:
header.doc_type_version = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_DEBUG, "Read DocTypeVersion attribute: {}", header.doc_type_version);
break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
return header;
}
DecoderErrorOr<void> Reader::parse_initial_data()
{
Streamer streamer { m_data };
auto first_element_id = TRY_READ(streamer.read_variable_size_integer(false));
dbgln_if(MATROSKA_TRACE_DEBUG, "First element ID is {:#010x}\n", first_element_id);
if (first_element_id != EBML_MASTER_ELEMENT_ID)
return DecoderError::corrupted("First element was not an EBML header"sv);
m_header = TRY(parse_ebml_header(streamer));
dbgln_if(MATROSKA_DEBUG, "Parsed EBML header");
auto root_element_id = TRY_READ(streamer.read_variable_size_integer(false));
if (root_element_id != SEGMENT_ELEMENT_ID)
return DecoderError::corrupted("Second element was not a segment element"sv);
m_segment_contents_size = TRY_READ(streamer.read_variable_size_integer());
m_segment_contents_position = streamer.position();
dbgln_if(MATROSKA_TRACE_DEBUG, "Segment is at {} with size {}, available size is {}", m_segment_contents_position, m_segment_contents_size, m_data.size() - m_segment_contents_position);
m_segment_contents_size = min(m_segment_contents_size, m_data.size() - m_segment_contents_position);
return {};
}
static DecoderErrorOr<void> parse_seek_head(Streamer& streamer, size_t base_position, HashMap<u32, size_t>& table)
{
TRY(parse_master_element(streamer, "SeekHead"sv, [&](u64 seek_head_child_id) -> DecoderErrorOr<IterationDecision> {
if (seek_head_child_id == SEEK_ELEMENT_ID) {
Optional<u64> seek_id;
Optional<u64> seek_position;
TRY(parse_master_element(streamer, "Seek"sv, [&](u64 seek_entry_child_id) -> DecoderErrorOr<IterationDecision> {
switch (seek_entry_child_id) {
case SEEK_ID_ELEMENT_ID:
seek_id = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Seek Element ID value {:#010x}", seek_id.value());
break;
case SEEK_POSITION_ELEMENT_ID:
seek_position = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Seek Position value {}", seek_position.value());
break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
if (!seek_id.has_value())
return DecoderError::corrupted("Seek entry is missing the element ID"sv);
if (!seek_position.has_value())
return DecoderError::corrupted("Seek entry is missing the seeking position"sv);
if (seek_id.value() > NumericLimits<u32>::max())
return DecoderError::corrupted("Seek entry's element ID is too large"sv);
dbgln_if(MATROSKA_TRACE_DEBUG, "Seek entry found with ID {:#010x} and position {} offset from SeekHead at {}", seek_id.value(), seek_position.value(), base_position);
// FIXME: SeekHead can reference another SeekHead, we should recursively parse all SeekHeads.
if (table.contains(seek_id.value())) {
dbgln_if(MATROSKA_DEBUG, "Warning: Duplicate seek entry with ID {:#010x} at position {}", seek_id.value(), seek_position.value());
return IterationDecision::Continue;
}
DECODER_TRY_ALLOC(table.try_set(seek_id.release_value(), base_position + seek_position.release_value()));
} else {
dbgln_if(MATROSKA_TRACE_DEBUG, "Unknown SeekHead child element ID {:#010x}", seek_head_child_id);
}
return IterationDecision::Continue;
}));
return {};
}
DecoderErrorOr<Optional<size_t>> Reader::find_first_top_level_element_with_id([[maybe_unused]] StringView element_name, u32 element_id)
{
dbgln_if(MATROSKA_DEBUG, "====== Finding element {} with ID {:#010x} ======", element_name, element_id);
if (m_seek_entries.contains(element_id)) {
dbgln_if(MATROSKA_TRACE_DEBUG, "Cache hit!");
return m_seek_entries.get(element_id).release_value();
}
Streamer streamer { m_data };
if (m_last_top_level_element_position != 0)
TRY_READ(streamer.seek_to_position(m_last_top_level_element_position));
else
TRY_READ(streamer.seek_to_position(m_segment_contents_position));
Optional<size_t> position;
while (streamer.position() < m_segment_contents_position + m_segment_contents_size) {
auto found_element_id = TRY_READ(streamer.read_variable_size_integer(false));
auto found_element_position = streamer.position();
dbgln_if(MATROSKA_TRACE_DEBUG, "Found element ID {:#010x} with position {}.", found_element_id, found_element_position);
if (found_element_id == SEEK_HEAD_ELEMENT_ID) {
dbgln_if(MATROSKA_TRACE_DEBUG, "Found SeekHead, parsing it into the lookup table.");
m_seek_entries.clear();
TRY(parse_seek_head(streamer, found_element_position, m_seek_entries));
m_last_top_level_element_position = 0;
if (m_seek_entries.contains(element_id)) {
dbgln_if(MATROSKA_TRACE_DEBUG, "SeekHead hit!");
position = m_seek_entries.get(element_id).release_value();
break;
}
continue;
}
auto result = streamer.read_unknown_element();
if (result.is_error())
return DecoderError::format(DecoderErrorCategory::Corrupted, "While seeking to {}: {}", element_name, result.release_error().string_literal());
m_last_top_level_element_position = streamer.position();
DECODER_TRY_ALLOC(m_seek_entries.try_set(found_element_id, found_element_position));
if (found_element_id == element_id) {
position = found_element_position;
break;
}
dbgln_if(MATROSKA_TRACE_DEBUG, "Skipped to position {}.", m_last_top_level_element_position);
}
return position;
}
static DecoderErrorOr<SegmentInformation> parse_information(Streamer& streamer)
{
SegmentInformation segment_information;
TRY(parse_master_element(streamer, "Segment Information"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case TIMESTAMP_SCALE_ID:
segment_information.set_timestamp_scale(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_DEBUG, "Read TimestampScale attribute: {}", segment_information.timestamp_scale());
break;
case MUXING_APP_ID:
segment_information.set_muxing_app(TRY_READ(streamer.read_string()));
dbgln_if(MATROSKA_DEBUG, "Read MuxingApp attribute: {}", segment_information.muxing_app().as_string());
break;
case WRITING_APP_ID:
segment_information.set_writing_app(TRY_READ(streamer.read_string()));
dbgln_if(MATROSKA_DEBUG, "Read WritingApp attribute: {}", segment_information.writing_app().as_string());
break;
case DURATION_ID:
segment_information.set_duration_unscaled(TRY_READ(streamer.read_float()));
dbgln_if(MATROSKA_DEBUG, "Read Duration attribute: {}", segment_information.duration_unscaled().value());
break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
return segment_information;
}
DecoderErrorOr<SegmentInformation> Reader::segment_information()
{
if (m_segment_information.has_value())
return m_segment_information.value();
auto position = TRY(find_first_top_level_element_with_id("Segment Information"sv, SEGMENT_INFORMATION_ELEMENT_ID));
if (!position.has_value())
return DecoderError::corrupted("No Segment Information element found"sv);
Streamer streamer { m_data };
TRY_READ(streamer.seek_to_position(position.release_value()));
m_segment_information = TRY(parse_information(streamer));
return m_segment_information.value();
}
DecoderErrorOr<void> Reader::ensure_tracks_are_parsed()
{
if (!m_tracks.is_empty())
return {};
auto position = TRY(find_first_top_level_element_with_id("Tracks"sv, TRACK_ELEMENT_ID));
if (!position.has_value())
return DecoderError::corrupted("No Tracks element found"sv);
Streamer streamer { m_data };
TRY_READ(streamer.seek_to_position(position.release_value()));
TRY(parse_tracks(streamer));
return {};
}
static DecoderErrorOr<TrackEntry::ColorFormat> parse_video_color_information(Streamer& streamer)
{
TrackEntry::ColorFormat color_format {};
TRY(parse_master_element(streamer, "Colour"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case PRIMARIES_ID:
color_format.color_primaries = static_cast<ColorPrimaries>(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Colour's Primaries attribute: {}", color_primaries_to_string(color_format.color_primaries));
break;
case TRANSFER_CHARACTERISTICS_ID:
color_format.transfer_characteristics = static_cast<TransferCharacteristics>(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Colour's TransferCharacteristics attribute: {}", transfer_characteristics_to_string(color_format.transfer_characteristics));
break;
case MATRIX_COEFFICIENTS_ID:
color_format.matrix_coefficients = static_cast<MatrixCoefficients>(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Colour's MatrixCoefficients attribute: {}", matrix_coefficients_to_string(color_format.matrix_coefficients));
break;
case RANGE_ID:
color_format.range = static_cast<TrackEntry::ColorRange>(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Colour's Range attribute: {}", to_underlying(color_format.range));
break;
case BITS_PER_CHANNEL_ID:
color_format.bits_per_channel = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Colour's BitsPerChannel attribute: {}", color_format.bits_per_channel);
break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
return color_format;
}
static DecoderErrorOr<TrackEntry::VideoTrack> parse_video_track_information(Streamer& streamer)
{
TrackEntry::VideoTrack video_track {};
TRY(parse_master_element(streamer, "VideoTrack"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case PIXEL_WIDTH_ID:
video_track.pixel_width = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read VideoTrack's PixelWidth attribute: {}", video_track.pixel_width);
break;
case PIXEL_HEIGHT_ID:
video_track.pixel_height = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read VideoTrack's PixelHeight attribute: {}", video_track.pixel_height);
break;
case COLOR_ENTRY_ID:
video_track.color_format = TRY(parse_video_color_information(streamer));
break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
return video_track;
}
static DecoderErrorOr<TrackEntry::AudioTrack> parse_audio_track_information(Streamer& streamer)
{
TrackEntry::AudioTrack audio_track {};
TRY(parse_master_element(streamer, "AudioTrack"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case CHANNELS_ID:
audio_track.channels = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read AudioTrack's Channels attribute: {}", audio_track.channels);
break;
case BIT_DEPTH_ID:
audio_track.bit_depth = TRY_READ(streamer.read_u64());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read AudioTrack's BitDepth attribute: {}", audio_track.bit_depth);
break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
return audio_track;
}
static DecoderErrorOr<NonnullRefPtr<TrackEntry>> parse_track_entry(Streamer& streamer)
{
auto track_entry = DECODER_TRY_ALLOC(try_make_ref_counted<TrackEntry>());
TRY(parse_master_element(streamer, "Track"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case TRACK_NUMBER_ID:
track_entry->set_track_number(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read TrackNumber attribute: {}", track_entry->track_number());
break;
case TRACK_UID_ID:
track_entry->set_track_uid(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read TrackUID attribute: {}", track_entry->track_uid());
break;
case TRACK_TYPE_ID:
track_entry->set_track_type(static_cast<TrackEntry::TrackType>(TRY_READ(streamer.read_u64())));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read TrackType attribute: {}", to_underlying(track_entry->track_type()));
break;
case TRACK_LANGUAGE_ID:
track_entry->set_language(DECODER_TRY_ALLOC(String::from_byte_string(TRY_READ(streamer.read_string()))));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Track's Language attribute: {}", track_entry->language());
break;
case TRACK_CODEC_ID:
track_entry->set_codec_id(DECODER_TRY_ALLOC(String::from_byte_string(TRY_READ(streamer.read_string()))));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Track's CodecID attribute: {}", track_entry->codec_id());
break;
case TRACK_CODEC_PRIVATE: {
auto codec_private_data = TRY_READ(streamer.read_raw_octets(TRY_READ(streamer.read_variable_size_integer())));
DECODER_TRY_ALLOC(track_entry->set_codec_private_data(codec_private_data));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Track's CodecID attribute: {}", track_entry->codec_id());
break;
}
case TRACK_TIMESTAMP_SCALE_ID:
track_entry->set_timestamp_scale(TRY_READ(streamer.read_float()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Track's TrackTimestampScale attribute: {}", track_entry->timestamp_scale());
break;
case TRACK_OFFSET_ID:
track_entry->set_timestamp_offset(TRY_READ(streamer.read_variable_size_signed_integer()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read Track's TrackOffset attribute: {}", track_entry->timestamp_offset());
break;
case TRACK_VIDEO_ID:
track_entry->set_video_track(TRY(parse_video_track_information(streamer)));
break;
case TRACK_AUDIO_ID:
track_entry->set_audio_track(TRY(parse_audio_track_information(streamer)));
break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
return track_entry;
}
DecoderErrorOr<void> Reader::parse_tracks(Streamer& streamer)
{
TRY(parse_master_element(streamer, "Tracks"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
if (element_id == TRACK_ENTRY_ID) {
auto track_entry = TRY(parse_track_entry(streamer));
dbgln_if(MATROSKA_DEBUG, "Parsed track {}", track_entry->track_number());
DECODER_TRY_ALLOC(m_tracks.try_set(track_entry->track_number(), track_entry));
} else {
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
return {};
}
DecoderErrorOr<void> Reader::for_each_track(TrackEntryCallback callback)
{
TRY(ensure_tracks_are_parsed());
for (auto const& track_entry : m_tracks) {
auto decision = TRY(callback(track_entry.value));
if (decision == IterationDecision::Break)
break;
}
return {};
}
DecoderErrorOr<void> Reader::for_each_track_of_type(TrackEntry::TrackType type, TrackEntryCallback callback)
{
return for_each_track([&](TrackEntry const& track_entry) -> DecoderErrorOr<IterationDecision> {
if (track_entry.track_type() != type)
return IterationDecision::Continue;
return callback(track_entry);
});
}
DecoderErrorOr<NonnullRefPtr<TrackEntry>> Reader::track_for_track_number(u64 track_number)
{
TRY(ensure_tracks_are_parsed());
auto optional_track_entry = m_tracks.get(track_number);
if (!optional_track_entry.has_value())
return DecoderError::format(DecoderErrorCategory::Invalid, "No track found with number {}", track_number);
return *optional_track_entry.release_value();
}
DecoderErrorOr<size_t> Reader::track_count()
{
TRY(ensure_tracks_are_parsed());
return m_tracks.size();
}
constexpr size_t get_element_id_size(u32 element_id)
{
return sizeof(element_id) - (count_leading_zeroes(element_id) / 8);
}
static DecoderErrorOr<Cluster> parse_cluster(Streamer& streamer, u64 timestamp_scale)
{
Optional<u64> timestamp;
auto first_element_position = TRY(parse_master_element(streamer, "Cluster"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case TIMESTAMP_ID:
timestamp = TRY_READ(streamer.read_u64());
return IterationDecision::Break;
default:
TRY_READ(streamer.read_unknown_element());
}
return IterationDecision::Continue;
}));
if (!timestamp.has_value())
return DecoderError::corrupted("Cluster was missing a timestamp"sv);
if (first_element_position == 0)
return DecoderError::corrupted("Cluster had no children"sv);
dbgln_if(MATROSKA_TRACE_DEBUG, "Seeking back to position {}", first_element_position);
TRY_READ(streamer.seek_to_position(first_element_position));
Cluster cluster;
cluster.set_timestamp(Duration::from_nanoseconds(timestamp.release_value() * timestamp_scale));
return cluster;
}
static DecoderErrorOr<Block> parse_simple_block(Streamer& streamer, Duration cluster_timestamp, u64 segment_timestamp_scale, TrackEntry const& track)
{
Block block;
auto content_size = TRY_READ(streamer.read_variable_size_integer());
auto position_before_track_number = streamer.position();
block.set_track_number(TRY_READ(streamer.read_variable_size_integer()));
// https://www.matroska.org/technical/notes.html
// Block Timestamps:
// The Block Element and SimpleBlock Element store their timestamps as signed integers,
// relative to the Cluster\Timestamp value of the Cluster they are stored in. To get the
// timestamp of a Block or SimpleBlock in nanoseconds you have to use the following formula:
// `( Cluster\Timestamp + ( block timestamp * TrackTimestampScale ) ) * TimestampScale`
//
// When a CodecDelay Element is set, its value MUST be subtracted from each Block timestamp
// of that track. To get the timestamp in nanoseconds of the first frame in a Block or
// SimpleBlock, the formula becomes:
// `( ( Cluster\Timestamp + ( block timestamp * TrackTimestampScale ) ) * TimestampScale ) - CodecDelay`
auto raw_timestamp_offset = TRY_READ(streamer.read_i16());
Checked<i64> timestamp_offset_ns = AK::clamp_to<i64>(static_cast<double>(raw_timestamp_offset * AK::clamp_to<i64>(segment_timestamp_scale)) * track.timestamp_scale());
timestamp_offset_ns.saturating_sub(AK::clamp_to<i64>(track.codec_delay()));
// This is only mentioned in the elements specification under TrackOffset.
// https://www.matroska.org/technical/elements.html
timestamp_offset_ns.saturating_add(AK::clamp_to<i64>(track.timestamp_offset()));
Duration timestamp_offset = Duration::from_nanoseconds(timestamp_offset_ns.value());
block.set_timestamp(cluster_timestamp + timestamp_offset);
auto flags = TRY_READ(streamer.read_octet());
block.set_only_keyframes((flags & (1u << 7u)) != 0);
block.set_invisible((flags & (1u << 3u)) != 0);
block.set_lacing(static_cast<Block::Lacing>((flags & 0b110u) >> 1u));
block.set_discardable((flags & 1u) != 0);
auto total_frame_content_size = content_size - (streamer.position() - position_before_track_number);
Vector<ReadonlyBytes> frames;
if (block.lacing() == Block::Lacing::EBML) {
auto octets_read_before_frame_sizes = streamer.octets_read();
auto frame_count = TRY_READ(streamer.read_octet()) + 1;
Vector<u64> frame_sizes;
frame_sizes.ensure_capacity(frame_count);
u64 frame_size_sum = 0;
u64 previous_frame_size;
auto first_frame_size = TRY_READ(streamer.read_variable_size_integer());
frame_sizes.append(first_frame_size);
frame_size_sum += first_frame_size;
previous_frame_size = first_frame_size;
for (int i = 0; i < frame_count - 2; i++) {
auto frame_size_difference = TRY_READ(streamer.read_variable_size_signed_integer());
u64 frame_size;
// FIXME: x - (-y) == x + y?
if (frame_size_difference < 0)
frame_size = previous_frame_size - (-frame_size_difference);
else
frame_size = previous_frame_size + frame_size_difference;
frame_sizes.append(frame_size);
frame_size_sum += frame_size;
previous_frame_size = frame_size;
}
frame_sizes.append(total_frame_content_size - frame_size_sum - (streamer.octets_read() - octets_read_before_frame_sizes));
for (int i = 0; i < frame_count; i++) {
// FIXME: ReadonlyBytes instead of copying the frame data?
auto current_frame_size = frame_sizes.at(i);
frames.append(TRY_READ(streamer.read_raw_octets(current_frame_size)));
}
} else if (block.lacing() == Block::Lacing::FixedSize) {
auto frame_count = TRY_READ(streamer.read_octet()) + 1;
auto individual_frame_size = total_frame_content_size / frame_count;
for (int i = 0; i < frame_count; i++)
frames.append(TRY_READ(streamer.read_raw_octets(individual_frame_size)));
} else {
frames.append(TRY_READ(streamer.read_raw_octets(total_frame_content_size)));
}
block.set_frames(move(frames));
return block;
}
DecoderErrorOr<SampleIterator> Reader::create_sample_iterator(u64 track_number)
{
auto optional_position = TRY(find_first_top_level_element_with_id("Cluster"sv, CLUSTER_ELEMENT_ID));
if (!optional_position.has_value())
return DecoderError::corrupted("No clusters are present in the segment"sv);
ReadonlyBytes segment_view = m_data.slice(m_segment_contents_position, m_segment_contents_size);
// We need to have the element ID included so that the iterator knows where it is.
auto position = optional_position.value() - get_element_id_size(CLUSTER_ELEMENT_ID) - m_segment_contents_position;
dbgln_if(MATROSKA_DEBUG, "Creating sample iterator starting at {} relative to segment at {}", position, m_segment_contents_position);
return SampleIterator(this->m_mapped_file, segment_view, TRY(track_for_track_number(track_number)), TRY(segment_information()).timestamp_scale(), position);
}
static DecoderErrorOr<CueTrackPosition> parse_cue_track_position(Streamer& streamer)
{
CueTrackPosition track_position;
bool had_cluster_position = false;
TRY_READ(parse_master_element(streamer, "CueTrackPositions"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case CUE_TRACK_ID:
track_position.set_track_number(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read CueTrackPositions track number {}", track_position.track_number());
break;
case CUE_CLUSTER_POSITION_ID:
track_position.set_cluster_position(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read CueTrackPositions cluster position {}", track_position.cluster_position());
had_cluster_position = true;
break;
case CUE_RELATIVE_POSITION_ID:
track_position.set_block_offset(TRY_READ(streamer.read_u64()));
dbgln_if(MATROSKA_TRACE_DEBUG, "Read CueTrackPositions relative position {}", track_position.block_offset());
break;
case CUE_CODEC_STATE_ID:
// Mandatory in spec, but not present in files? 0 means use TrackEntry's codec state.
// FIXME: Do something with this value.
dbgln_if(MATROSKA_DEBUG, "Found CodecState, skipping");
TRY_READ(streamer.read_unknown_element());
break;
case CUE_REFERENCE_ID:
return DecoderError::not_implemented();
default:
TRY_READ(streamer.read_unknown_element());
break;
}
return IterationDecision::Continue;
}));
if (track_position.track_number() == 0)
return DecoderError::corrupted("Track number was not present or 0"sv);
if (!had_cluster_position)
return DecoderError::corrupted("Cluster was missing the cluster position"sv);
return track_position;
}
static DecoderErrorOr<CuePoint> parse_cue_point(Streamer& streamer, u64 timestamp_scale)
{
CuePoint cue_point;
TRY(parse_master_element(streamer, "CuePoint"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case CUE_TIME_ID: {
// On https://www.matroska.org/technical/elements.html, spec says of the CueTime element:
// > Absolute timestamp of the seek point, expressed in Matroska Ticks -- ie in nanoseconds; see timestamp-ticks.
// Matroska Ticks are specified in https://www.matroska.org/technical/notes.html:
// > For such elements, the timestamp value is stored directly in nanoseconds.
// However, my test files appear to use Segment Ticks, which uses the segment's timestamp scale, and Mozilla's nestegg parser agrees:
// https://github.com/mozilla/nestegg/tree/ec6adfbbf979678e3058cc4695257366f39e290b/src/nestegg.c#L1941
// https://github.com/mozilla/nestegg/tree/ec6adfbbf979678e3058cc4695257366f39e290b/src/nestegg.c#L2411-L2416
// https://github.com/mozilla/nestegg/tree/ec6adfbbf979678e3058cc4695257366f39e290b/src/nestegg.c#L1383-L1392
// Other fields that specify Matroska Ticks may also use Segment Ticks instead, who knows :^(
auto timestamp = Duration::from_nanoseconds(static_cast<i64>(TRY_READ(streamer.read_u64()) * timestamp_scale));
cue_point.set_timestamp(timestamp);
dbgln_if(MATROSKA_DEBUG, "Read CuePoint timestamp {}ms", cue_point.timestamp().to_milliseconds());
break;
}
case CUE_TRACK_POSITIONS_ID: {
auto track_position = TRY_READ(parse_cue_track_position(streamer));
DECODER_TRY_ALLOC(cue_point.track_positions().try_set(track_position.track_number(), track_position));
break;
}
default:
TRY_READ(streamer.read_unknown_element());
break;
}
return IterationDecision::Continue;
}));
if (cue_point.timestamp().is_negative())
return DecoderError::corrupted("CuePoint was missing a timestamp"sv);
if (cue_point.track_positions().is_empty())
return DecoderError::corrupted("CuePoint was missing track positions"sv);
return cue_point;
}
DecoderErrorOr<void> Reader::parse_cues(Streamer& streamer)
{
m_cues.clear();
TRY(parse_master_element(streamer, "Cues"sv, [&](u64 element_id) -> DecoderErrorOr<IterationDecision> {
switch (element_id) {
case CUE_POINT_ID: {
auto cue_point = TRY(parse_cue_point(streamer, TRY(segment_information()).timestamp_scale()));
// FIXME: Verify that these are already in order of timestamp. If they are not, return a corrupted error for now,
// but if it turns out that Matroska files with out-of-order cue points are valid, sort them instead.
for (auto track_position_entry : cue_point.track_positions()) {
if (!m_cues.contains(track_position_entry.key))
DECODER_TRY_ALLOC(m_cues.try_set(track_position_entry.key, Vector<CuePoint>()));
Vector<CuePoint>& cue_points_for_track = m_cues.get(track_position_entry.key).release_value();
cue_points_for_track.append(cue_point);
}
break;
}
default:
return DecoderError::format(DecoderErrorCategory::Corrupted, "Unknown Cues child ID {:#010x}", element_id);
}
return IterationDecision::Continue;
}));
return {};
}
DecoderErrorOr<void> Reader::ensure_cues_are_parsed()
{
if (m_cues_have_been_parsed)
return {};
auto position = TRY(find_first_top_level_element_with_id("Cues"sv, CUES_ID));
if (!position.has_value())
return DecoderError::corrupted("No Tracks element found"sv);
Streamer streamer { m_data };
TRY_READ(streamer.seek_to_position(position.release_value()));
TRY(parse_cues(streamer));
m_cues_have_been_parsed = true;
return {};
}
DecoderErrorOr<void> Reader::seek_to_cue_for_timestamp(SampleIterator& iterator, Duration const& timestamp)
{
auto const& cue_points = MUST(cue_points_for_track(iterator.m_track->track_number())).release_value();
// Take a guess at where in the cues the timestamp will be and correct from there.
auto duration = TRY(segment_information()).duration();
size_t index = 0;
if (duration.has_value())
index = clamp(((timestamp.to_nanoseconds() * cue_points.size()) / TRY(segment_information()).duration()->to_nanoseconds()), 0, cue_points.size() - 1);
CuePoint const* prev_cue_point = &cue_points[index];
dbgln_if(MATROSKA_DEBUG, "Finding Matroska cue points for timestamp {}ms starting from cue at {}ms", timestamp.to_milliseconds(), prev_cue_point->timestamp().to_milliseconds());
if (prev_cue_point->timestamp() == timestamp) {
TRY(iterator.seek_to_cue_point(*prev_cue_point));
return {};
}
if (prev_cue_point->timestamp() > timestamp) {
while (index > 0 && prev_cue_point->timestamp() > timestamp) {
prev_cue_point = &cue_points[--index];
dbgln_if(MATROSKA_DEBUG, "Checking previous cue point {}ms", prev_cue_point->timestamp().to_milliseconds());
}
TRY(iterator.seek_to_cue_point(*prev_cue_point));
return {};
}
while (++index < cue_points.size()) {
auto const& cue_point = cue_points[index];
dbgln_if(MATROSKA_DEBUG, "Checking future cue point {}ms", cue_point.timestamp().to_milliseconds());
if (cue_point.timestamp() > timestamp)
break;
prev_cue_point = &cue_point;
}
TRY(iterator.seek_to_cue_point(*prev_cue_point));
return {};
}
static DecoderErrorOr<void> search_clusters_for_keyframe_before_timestamp(SampleIterator& iterator, Duration const& timestamp)
{
#if MATROSKA_DEBUG
size_t inter_frames_count;
#endif
Optional<SampleIterator> last_keyframe;
while (true) {
SampleIterator rewind_iterator = iterator;
auto block = TRY(iterator.next_block());
if (block.only_keyframes()) {
last_keyframe.emplace(rewind_iterator);
#if MATROSKA_DEBUG
inter_frames_count = 0;
#endif
}
if (block.timestamp() > timestamp)
break;
#if MATROSKA_DEBUG
inter_frames_count++;
#endif
}
if (last_keyframe.has_value()) {
#if MATROSKA_DEBUG
dbgln("Seeked to a keyframe with {} inter frames to skip", inter_frames_count);
#endif
iterator = last_keyframe.release_value();
}
return {};
}
DecoderErrorOr<bool> Reader::has_cues_for_track(u64 track_number)
{
TRY(ensure_cues_are_parsed());
return m_cues.contains(track_number);
}
DecoderErrorOr<SampleIterator> Reader::seek_to_random_access_point(SampleIterator iterator, Duration timestamp)
{
if (TRY(has_cues_for_track(iterator.m_track->track_number()))) {
TRY(seek_to_cue_for_timestamp(iterator, timestamp));
VERIFY(iterator.last_timestamp().has_value());
return iterator;
}
if (!iterator.last_timestamp().has_value() || timestamp < iterator.last_timestamp().value()) {
// If the timestamp is before the iterator's current position, then we need to start from the beginning of the Segment.
iterator = TRY(create_sample_iterator(iterator.m_track->track_number()));
TRY(search_clusters_for_keyframe_before_timestamp(iterator, timestamp));
return iterator;
}
TRY(search_clusters_for_keyframe_before_timestamp(iterator, timestamp));
return iterator;
}
DecoderErrorOr<Optional<Vector<CuePoint> const&>> Reader::cue_points_for_track(u64 track_number)
{
TRY(ensure_cues_are_parsed());
return m_cues.get(track_number);
}
DecoderErrorOr<Block> SampleIterator::next_block()
{
if (m_position >= m_data.size())
return DecoderError::with_description(DecoderErrorCategory::EndOfStream, "Still at end of stream :^)"sv);
Streamer streamer { m_data };
TRY_READ(streamer.seek_to_position(m_position));
Optional<Block> block;
while (streamer.has_octet()) {
#if MATROSKA_TRACE_DEBUG
auto element_position = streamer.position();
#endif
auto element_id = TRY_READ(streamer.read_variable_size_integer(false));
#if MATROSKA_TRACE_DEBUG
dbgln("Iterator found element with ID {:#010x} at offset {} within the segment.", element_id, element_position);
#endif
if (element_id == CLUSTER_ELEMENT_ID) {
dbgln_if(MATROSKA_DEBUG, " Iterator is parsing new cluster.");
m_current_cluster = TRY(parse_cluster(streamer, m_segment_timestamp_scale));
} else if (element_id == SIMPLE_BLOCK_ID) {
dbgln_if(MATROSKA_TRACE_DEBUG, " Iterator is parsing new block.");
auto candidate_block = TRY(parse_simple_block(streamer, m_current_cluster->timestamp(), m_segment_timestamp_scale, m_track));
if (candidate_block.track_number() == m_track->track_number())
block = move(candidate_block);
} else {
dbgln_if(MATROSKA_TRACE_DEBUG, " Iterator is skipping unknown element with ID {:#010x}.", element_id);
TRY_READ(streamer.read_unknown_element());
}
m_position = streamer.position();
if (block.has_value()) {
m_last_timestamp = block->timestamp();
return block.release_value();
}
}
m_current_cluster.clear();
return DecoderError::with_description(DecoderErrorCategory::EndOfStream, "End of stream"sv);
}
DecoderErrorOr<void> SampleIterator::seek_to_cue_point(CuePoint const& cue_point)
{
// This is a private function. The position getter can return optional, but the caller should already know that this track has a position.
auto const& cue_position = cue_point.position_for_track(m_track->track_number()).release_value();
Streamer streamer { m_data };
TRY_READ(streamer.seek_to_position(cue_position.cluster_position()));
auto element_id = TRY_READ(streamer.read_variable_size_integer(false));
if (element_id != CLUSTER_ELEMENT_ID)
return DecoderError::corrupted("Cue point's cluster position didn't point to a cluster"sv);
m_current_cluster = TRY(parse_cluster(streamer, m_segment_timestamp_scale));
dbgln_if(MATROSKA_DEBUG, "SampleIterator set to cue point at timestamp {}ms", m_current_cluster->timestamp().to_milliseconds());
m_position = streamer.position() + cue_position.block_offset();
m_last_timestamp = cue_point.timestamp();
return {};
}
ErrorOr<ByteString> Streamer::read_string()
{
auto string_length = TRY(read_variable_size_integer());
if (remaining() < string_length)
return Error::from_string_literal("String length extends past the end of the stream");
auto string_data = data_as_chars();
auto string_value = ByteString(string_data, strnlen(string_data, string_length));
TRY(read_raw_octets(string_length));
return string_value;
}
ErrorOr<u8> Streamer::read_octet()
{
if (!has_octet()) {
dbgln_if(MATROSKA_TRACE_DEBUG, "Ran out of stream data");
return Error::from_string_literal("Stream is out of data");
}
u8 byte = *data();
m_octets_read.last()++;
m_position++;
return byte;
}
ErrorOr<i16> Streamer::read_i16()
{
return (TRY(read_octet()) << 8) | TRY(read_octet());
}
ErrorOr<u64> Streamer::read_variable_size_integer(bool mask_length)
{
dbgln_if(MATROSKA_TRACE_DEBUG, "Reading VINT from offset {:p}", position());
auto length_descriptor = TRY(read_octet());
dbgln_if(MATROSKA_TRACE_DEBUG, "Reading VINT, first byte is {:#02x}", length_descriptor);
if (length_descriptor == 0)
return Error::from_string_literal("read_variable_size_integer: Length descriptor has no terminating set bit");
size_t length = 0;
while (length < 8) {
if (((length_descriptor >> (8 - length)) & 1) == 1)
break;
length++;
}
dbgln_if(MATROSKA_TRACE_DEBUG, "Reading VINT of total length {}", length);
if (length > 8)
return Error::from_string_literal("read_variable_size_integer: Length is too large");
u64 result;
if (mask_length)
result = length_descriptor & ~(1u << (8 - length));
else
result = length_descriptor;
dbgln_if(MATROSKA_TRACE_DEBUG, "Beginning of VINT is {:#02x}", result);
for (size_t i = 1; i < length; i++) {
u8 next_octet = TRY(read_octet());
dbgln_if(MATROSKA_TRACE_DEBUG, "Read octet of {:#02x}", next_octet);
result = (result << 8u) | next_octet;
dbgln_if(MATROSKA_TRACE_DEBUG, "New result is {:#010x}", result);
}
return result;
}
ErrorOr<i64> Streamer::read_variable_size_signed_integer()
{
auto length_descriptor = TRY(read_octet());
if (length_descriptor == 0)
return Error::from_string_literal("read_variable_sized_signed_integer: Length descriptor has no terminating set bit");
i64 length = 0;
while (length < 8) {
if (((length_descriptor >> (8 - length)) & 1) == 1)
break;
length++;
}
if (length > 8)
return Error::from_string_literal("read_variable_size_integer: Length is too large");
i64 result = length_descriptor & ~(1u << (8 - length));
for (i64 i = 1; i < length; i++) {
u8 next_octet = TRY(read_octet());
result = (result << 8u) | next_octet;
}
result -= AK::exp2<i64>(length * 7 - 1) - 1;
return result;
}
ErrorOr<ReadonlyBytes> Streamer::read_raw_octets(size_t num_octets)
{
if (remaining() < num_octets)
return Error::from_string_literal("Tried to drop octets past the end of the stream");
ReadonlyBytes result = { data(), num_octets };
m_position += num_octets;
m_octets_read.last() += num_octets;
return result;
}
ErrorOr<u64> Streamer::read_u64()
{
auto integer_length = TRY(read_variable_size_integer());
u64 result = 0;
for (size_t i = 0; i < integer_length; i++) {
result = (result << 8u) + TRY(read_octet());
}
return result;
}
ErrorOr<double> Streamer::read_float()
{
auto length = TRY(read_variable_size_integer());
if (length != 4u && length != 8u)
return Error::from_string_literal("Float size must be 4 or 8 bytes");
union {
u64 value;
float float_value;
double double_value;
} read_data;
read_data.value = 0;
for (size_t i = 0; i < length; i++) {
read_data.value = (read_data.value << 8u) + TRY(read_octet());
}
if (length == 4u)
return read_data.float_value;
return read_data.double_value;
}
ErrorOr<void> Streamer::read_unknown_element()
{
auto element_length = TRY(read_variable_size_integer());
dbgln_if(MATROSKA_TRACE_DEBUG, "Skipping unknown element of size {}.", element_length);
TRY(read_raw_octets(element_length));
return {};
}
ErrorOr<void> Streamer::seek_to_position(size_t position)
{
if (position >= m_data.size())
return Error::from_string_literal("Attempted to seek past the end of the stream");
m_position = position;
return {};
}
}
