Move movie runtime support to frontend

engine/Age.Engine.Frontend/IMovieDecoder.cs

@@ -0,0 +1,35 @@
+using System;
+using Age.Engine.Model;
+using Age.Engine.Sys4;
+
+internal readonly record struct MovieAudioInfo(int SampleRate, int Channels);
+internal sealed record MovieAudioChunk(float[] InterleavedStereo, int FrameCount, long PresentationTimeMs);
+
+/// <summary>
+/// Platform-neutral movie playback boundary. Construction is synchronous so metadata needed by the VM is
+/// available before op 0x236 returns; frame delivery and completion remain asynchronous.
+/// </summary>
+internal interface IMovieDecoder : IDisposable
+{
+    long? StopTimeMs { get; }
+    long InitialPositionMs => 0;
+    bool IsCompleted { get; }
+    string? Failure { get; }
+    long? FirstFramePresentationTimeMs => null;
+    bool TryTakeFrame(out RgbaImage frame);
+    MovieAudioInfo? AudioInfo => null;
+    bool AudioDecodingCompleted => true;
+    bool TryTakeAudioChunk(out MovieAudioChunk chunk)
+    {
+        chunk = default!;
+        return false;
+    }
+    void AdvancePlaybackClock(long elapsedMilliseconds) { }
+    void MarkAudioSubmitted() { }
+}
+
+internal interface IMovieDecoderFactory
+{
+    IMovieDecoder Open(
+        MoviePayload movie, long initialPositionMs = 0, long? presentationDurationMs = null);
+}