Add isolated FFmpeg movie decoder shim

2026-07-22 00:17:27 -04:00
parent f53056818d
commit 760f84e218
16 changed files with 1118 additions and 36 deletions
--- a/godot/FfmpegMovieNative.cs
+++ b/godot/FfmpegMovieNative.cs
@@ -0,0 +1,162 @@
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+using Age.Engine.Sys4;
+using Microsoft.Win32.SafeHandles;
+
+internal readonly record struct FfmpegMovieInfo(
+    int Width,
+    int Height,
+    long StopTimeMs,
+    int FrameRateNumerator,
+    int FrameRateDenominator,
+    bool HasAudio);
+
+internal sealed record FfmpegVideoFrame(RgbaImage Image, long PresentationTimeMs);
+
+/// <summary>Sequential, unpaced access to the project-owned FFmpeg C ABI for isolated probes and playback.</summary>
+internal sealed class FfmpegMovieSession : IDisposable
+{
+    private FfmpegMovieHandle _handle;
+    public FfmpegMovieInfo Info { get; }
+
+    public FfmpegMovieSession(MoviePayload movie)
+    {
+        ArgumentNullException.ThrowIfNull(movie);
+        if (FfmpegMovieNative.AbiVersion() != 1)
+            throw new InvalidOperationException("unsupported age_movie_ffmpeg ABI version");
+
+        byte[] error = new byte[1024];
+        int result = FfmpegMovieNative.Open(movie.Bytes, (nuint)movie.Bytes.Length,
+            out _handle, out var nativeInfo, error, (nuint)error.Length);
+        if (result != 0 || _handle.IsInvalid)
+        {
+            _handle?.Dispose();
+            throw new InvalidDataException(
+                $"FFmpeg movie open failed for {movie.Name}: {FfmpegMovieNative.DecodeUtf8(error)}");
+        }
+        Info = new FfmpegMovieInfo(nativeInfo.Width, nativeInfo.Height, nativeInfo.StopTimeMs,
+            nativeInfo.FrameRateNumerator, nativeInfo.FrameRateDenominator, nativeInfo.HasAudio != 0);
+        if (Info.Width <= 0 || Info.Height <= 0 || Info.StopTimeMs <= 0)
+        {
+            _handle.Dispose();
+            throw new InvalidDataException(
+                $"FFmpeg returned invalid metadata for {movie.Name}: {Info.Width}x{Info.Height}, {Info.StopTimeMs} ms");
+        }
+    }
+
+    public bool TryDecodeNextVideoFrame(out FfmpegVideoFrame frame)
+    {
+        ObjectDisposedException.ThrowIf(_handle.IsClosed, this);
+        byte[] pixels = new byte[checked(Info.Width * Info.Height * 4)];
+        int result = FfmpegMovieNative.DecodeVideo(_handle, pixels, (nuint)pixels.Length, out long ptsMs);
+        if (result == FfmpegMovieNative.EndOfFile)
+        {
+            frame = default!;
+            return false;
+        }
+        if (result != FfmpegMovieNative.Frame)
+            throw new InvalidDataException($"FFmpeg movie decode failed: {FfmpegMovieNative.LastError(_handle)}");
+        frame = new FfmpegVideoFrame(new RgbaImage(Info.Width, Info.Height, pixels), ptsMs);
+        return true;
+    }
+
+    public void Dispose() => _handle.Dispose();
+}
+
+internal sealed class FfmpegMovieHandle : SafeHandleZeroOrMinusOneIsInvalid
+{
+    private FfmpegMovieHandle() : base(ownsHandle: true) { }
+    protected override bool ReleaseHandle()
+    {
+        FfmpegMovieNative.Close(handle);
+        return true;
+    }
+}
+
+internal static class FfmpegMovieNative
+{
+    internal const int EndOfFile = 0;
+    internal const int Frame = 1;
+    private const string LibraryName = "age_movie_ffmpeg";
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct NativeInfo
+    {
+        public int Width;
+        public int Height;
+        public long StopTimeMs;
+        public int FrameRateNumerator;
+        public int FrameRateDenominator;
+        public int HasAudio;
+    }
+
+    static FfmpegMovieNative()
+    {
+        NativeLibrary.SetDllImportResolver(typeof(FfmpegMovieNative).Assembly, ResolveLibrary);
+    }
+
+    private static IntPtr ResolveLibrary(string libraryName, System.Reflection.Assembly assembly,
+                                         DllImportSearchPath? searchPath)
+    {
+        if (!string.Equals(libraryName, LibraryName, StringComparison.Ordinal)) return IntPtr.Zero;
+        string fileName = OperatingSystem.IsWindows()
+            ? "age_movie_ffmpeg.dll"
+            : OperatingSystem.IsMacOS() ? "libage_movie_ffmpeg.dylib" : "libage_movie_ffmpeg.so";
+        string? configured = Environment.GetEnvironmentVariable("AGE_FFMPEG_NATIVE_DIR");
+        string rid = OperatingSystem.IsWindows() ? "win-x64"
+            : OperatingSystem.IsMacOS() ? (RuntimeInformation.ProcessArchitecture == Architecture.Arm64 ? "osx-arm64" : "osx-x64")
+            : "linux-x64";
+        string[] candidates =
+        {
+            configured == null ? "" : Path.Combine(configured, fileName),
+            Path.Combine(AppContext.BaseDirectory, fileName),
+            Path.Combine(AppContext.BaseDirectory, "runtimes", rid, "native", fileName),
+        };
+        foreach (string candidate in candidates)
+            if (!string.IsNullOrEmpty(candidate) && File.Exists(candidate))
+                return NativeLibrary.Load(candidate);
+        throw new DllNotFoundException(
+            $"{fileName} was not found; set AGE_FFMPEG_NATIVE_DIR or package runtimes/{rid}/native");
+    }
+
+    internal static string DecodeUtf8(byte[] buffer)
+    {
+        int length = Array.IndexOf(buffer, (byte)0);
+        if (length < 0) length = buffer.Length;
+        return System.Text.Encoding.UTF8.GetString(buffer, 0, length);
+    }
+
+    internal static string LastError(FfmpegMovieHandle handle)
+    {
+        IntPtr text = LastErrorNative(handle);
+        return text == IntPtr.Zero ? "unknown decoder error" : Marshal.PtrToStringUTF8(text) ?? "unknown decoder error";
+    }
+
+    internal static uint AbiVersion() => AbiVersionNative();
+
+    [DllImport(LibraryName, EntryPoint = "age_movie_abi_version", CallingConvention = CallingConvention.Cdecl)]
+    private static extern uint AbiVersionNative();
+
+    [DllImport(LibraryName, EntryPoint = "age_movie_open", CallingConvention = CallingConvention.Cdecl)]
+    internal static extern int Open(
+        [In] byte[] bytes,
+        nuint length,
+        out FfmpegMovieHandle movie,
+        out NativeInfo info,
+        [Out] byte[] errorBuffer,
+        nuint errorBufferSize);
+
+    [DllImport(LibraryName, EntryPoint = "age_movie_decode_video", CallingConvention = CallingConvention.Cdecl)]
+    internal static extern int DecodeVideo(
+        FfmpegMovieHandle movie,
+        [Out] byte[] rgba,
+        nuint rgbaSize,
+        out long presentationTimeMs);
+
+    [DllImport(LibraryName, EntryPoint = "age_movie_last_error", CallingConvention = CallingConvention.Cdecl)]
+    private static extern IntPtr LastErrorNative(FfmpegMovieHandle movie);
+
+    [DllImport(LibraryName, EntryPoint = "age_movie_close", CallingConvention = CallingConvention.Cdecl)]
+    internal static extern void Close(IntPtr movie);
+}