LibVideo: Abstract media container format demuxing

This creates an abstract Demuxer class to allow multiple container
container formats to be easily used by video playback systems.

Userland/Libraries/LibVideo/Track.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2022, Gregory Bertilson <zaggy1024@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/HashFunctions.h>
+#include <AK/Traits.h>
+#include <AK/Types.h>
+
+namespace Video {
+
+enum class TrackType : u32 {
+    Video,
+    Audio,
+    Subtitles,
+};
+
+struct Track {
+public:
+    Track(TrackType type, size_t identifier)
+        : m_type(type)
+        , m_identifier(identifier)
+    {
+    }
+
+    TrackType type() { return m_type; }
+    size_t identifier() const { return m_identifier; }
+
+    bool operator==(Track const& other) const
+    {
+        return m_type == other.m_type && m_identifier == other.m_identifier;
+    }
+    unsigned hash() const
+    {
+        return pair_int_hash(to_underlying(m_type), m_identifier);
+    }
+
+private:
+    TrackType m_type;
+    size_t m_identifier;
+};
+
+}
+
+template<>
+struct AK::Traits<Video::Track> : public GenericTraits<Video::Track> {
+    static unsigned hash(Video::Track const& t) { return t.hash(); }
+};