blob: fd170864bc6be511e4cf78c2af2b07209ff98131 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
using System;
using System.Buffers.Binary;
using Jellyfin.MediaEncoding.Keyframes.Matroska.Models;
using NEbml.Core;
namespace Jellyfin.MediaEncoding.Keyframes.Matroska.Extensions;
/// <summary>
/// Extension methods for the <see cref="EbmlReader"/> class.
/// </summary>
internal static class EbmlReaderExtensions
{
/// <summary>
/// Traverses the current container to find the element with <paramref name="identifier"/> identifier.
/// </summary>
/// <param name="reader">An instance of <see cref="EbmlReader"/>.</param>
/// <param name="identifier">The element identifier.</param>
/// <returns>A value indicating whether the element was found.</returns>
internal static bool FindElement(this EbmlReader reader, ulong identifier)
{
while (reader.ReadNext())
{
if (reader.ElementId.EncodedValue == identifier)
{
return true;
}
}
return false;
}
/// <summary>
/// Reads the current position in the file as an unsigned integer converted from binary.
/// </summary>
/// <param name="reader">An instance of <see cref="EbmlReader"/>.</param>
/// <returns>The unsigned integer.</returns>
internal static uint ReadUIntFromBinary(this EbmlReader reader)
{
var buffer = new byte[4];
reader.ReadBinary(buffer, 0, 4);
return BinaryPrimitives.ReadUInt32BigEndian(buffer);
}
/// <summary>
/// Reads from the start of the file to retrieve the SeekHead segment.
/// </summary>
/// <param name="reader">An instance of <see cref="EbmlReader"/>.</param>
/// <returns>Instance of <see cref="SeekHead"/>.</returns>
internal static SeekHead ReadSeekHead(this EbmlReader reader)
{
reader = reader ?? throw new ArgumentNullException(nameof(reader));
if (reader.ElementPosition != 0)
{
throw new InvalidOperationException("File position must be at 0");
}
// Skip the header
if (!reader.FindElement(MatroskaConstants.SegmentContainer))
{
throw new InvalidOperationException("Expected a segment container");
}
reader.EnterContainer();
long? tracksPosition = null;
long? cuesPosition = null;
long? infoPosition = null;
// The first element should be a SeekHead otherwise we'll have to search manually
if (!reader.FindElement(MatroskaConstants.SeekHead))
{
throw new InvalidOperationException("Expected a SeekHead");
}
reader.EnterContainer();
while (reader.FindElement(MatroskaConstants.Seek))
{
reader.EnterContainer();
reader.ReadNext();
var type = (ulong)reader.ReadUIntFromBinary();
switch (type)
{
case MatroskaConstants.Tracks:
reader.ReadNext();
tracksPosition = (long)reader.ReadUInt();
break;
case MatroskaConstants.Cues:
reader.ReadNext();
cuesPosition = (long)reader.ReadUInt();
break;
case MatroskaConstants.Info:
reader.ReadNext();
infoPosition = (long)reader.ReadUInt();
break;
}
reader.LeaveContainer();
if (tracksPosition.HasValue && cuesPosition.HasValue && infoPosition.HasValue)
{
break;
}
}
reader.LeaveContainer();
if (!tracksPosition.HasValue || !cuesPosition.HasValue || !infoPosition.HasValue)
{
throw new InvalidOperationException("SeekHead is missing or does not contain Info, Tracks and Cues positions. SeekHead referencing another SeekHead is not supported");
}
return new SeekHead(infoPosition.Value, tracksPosition.Value, cuesPosition.Value);
}
/// <summary>
/// Reads from SegmentContainer to retrieve the Info segment.
/// </summary>
/// <param name="reader">An instance of <see cref="EbmlReader"/>.</param>
/// <param name="position">The position of the info segment relative to the Segment container.</param>
/// <returns>Instance of <see cref="Info"/>.</returns>
internal static Info ReadInfo(this EbmlReader reader, long position)
{
reader.ReadAt(position);
double? duration = null;
reader.EnterContainer();
// Mandatory element
reader.FindElement(MatroskaConstants.TimestampScale);
var timestampScale = reader.ReadUInt();
if (reader.FindElement(MatroskaConstants.Duration))
{
duration = reader.ReadFloat();
}
reader.LeaveContainer();
return new Info((long)timestampScale, duration);
}
/// <summary>
/// Enters the Tracks segment and reads all tracks to find the specified type.
/// </summary>
/// <param name="reader">Instance of <see cref="EbmlReader"/>.</param>
/// <param name="tracksPosition">The relative position of the tracks segment.</param>
/// <param name="type">The track type identifier.</param>
/// <returns>The first track number with the specified type.</returns>
/// <exception cref="InvalidOperationException">Stream type is not found.</exception>
internal static ulong FindFirstTrackNumberByType(this EbmlReader reader, long tracksPosition, ulong type)
{
reader.ReadAt(tracksPosition);
reader.EnterContainer();
while (reader.FindElement(MatroskaConstants.TrackEntry))
{
reader.EnterContainer();
// Mandatory element
reader.FindElement(MatroskaConstants.TrackNumber);
var trackNumber = reader.ReadUInt();
// Mandatory element
reader.FindElement(MatroskaConstants.TrackType);
var trackType = reader.ReadUInt();
reader.LeaveContainer();
if (trackType == MatroskaConstants.TrackTypeVideo)
{
reader.LeaveContainer();
return trackNumber;
}
}
reader.LeaveContainer();
throw new InvalidOperationException($"No stream with type {type} found");
}
}
|
