Fix media track marshalling and tests

LibVLCSharp.Tests/MediaTests.cs

@@ -101,7 +101,8 @@ namespace LibVLCSharp.Tests
         {
             var media = new Media(new LibVLC(), RealMp3Path);
             media.Parse();
-            Assert.AreEqual(1, media.Tracks);
+            Assert.AreEqual(media.Tracks.Single().Data.Audio.Channels, 2);
+            Assert.AreEqual(media.Tracks.Single().Data.Audio.Rate, 44100);
         }
 
         [Test]

LibVLCSharp/Shared/Helpers/MarshalExtensions.cs

@@ -54,10 +54,47 @@ namespace LibVLCSharp.Shared.Helpers
         /// </summary>
         /// <param name="s">TrackDescriptionStructure from interop</param>
         /// <returns>public TrackDescription to be consumed by the user</returns>
-        internal static MediaTrack Build(this MediaTrackStructure s) =>
-            new MediaTrack(s.Codec, s.OriginalFourcc, s.Id, s.TrackType, s.Profile, s.Level, s.Data, s.Bitrate,
-                Utf8StringMarshaler.GetInstance().MarshalNativeToManaged(s.Language) as string,
-                Utf8StringMarshaler.GetInstance().MarshalNativeToManaged(s.Description) as string);
+        internal static MediaTrack Build(this MediaTrackStructure s)
+        {
+            AudioTrack audioTrack = default;
+            VideoTrack videoTrack = default;
+            SubtitleTrack subtitleTrack = default;
+
+            switch (s.TrackType)
+            {
+                case TrackType.Audio:
+                    audioTrack = MarshalUtils.PtrToStructure<AudioTrack>(s.TrackData);
+                    break;
+                case TrackType.Video:
+                    videoTrack = MarshalUtils.PtrToStructure<VideoTrack>(s.TrackData);
+                    break;
+                case TrackType.Text:
+                    subtitleTrack = MarshalUtils.PtrToStructure<SubtitleTrackStructure>(s.TrackData).Build();
+                    break;
+                case TrackType.Unknown:
+                    break;
+            }
+
+            var language = Utf8StringMarshaler.GetInstance().MarshalNativeToManaged(s.Language) as string;
+            var des = Utf8StringMarshaler.GetInstance().MarshalNativeToManaged(s.Description) as string;
+
+            return new MediaTrack(s.Codec, 
+                s.OriginalFourcc, 
+                s.Id, 
+                s.TrackType, 
+                s.Profile, 
+                s.Level, 
+                new MediaTrackData(audioTrack, videoTrack, subtitleTrack), s.Bitrate,
+                language,
+                des);
+        }
+        
+        /// <summary>
+        /// Helper method that creates a user friendly type from the internal interop structure.
+        /// </summary>
+        /// <param name="s">SubtitleTrackStructure from interop</param>
+        /// <returns>public SubtitleTrack to be consumed by the user</returns>
+        internal static SubtitleTrack Build(this SubtitleTrackStructure s) => new SubtitleTrack(Utf8StringMarshaler.GetInstance().MarshalNativeToManaged(s.Encoding) as string);
 
         /// <summary>
         /// Helper method that creates a user friendly type from the internal interop structure.

LibVLCSharp/Shared/Helpers/MarshalUtils.cs

@@ -74,13 +74,13 @@ namespace LibVLCSharp.Shared.Helpers
             return resultList.ToArray();
         }
 
-        internal static TU[] Retrieve<T, TU>(IntPtr nativeRef, Func<IntPtr, IntPtr, uint> getRef, Func<IntPtr, T> retrieve,
+        internal static TU[] Retrieve<T, TU>(IntPtr nativeRef, ArrayOut getRef, Func<IntPtr, T> retrieve,
             Func<T, TU> create, Action<IntPtr, uint> releaseRef)
             where T : struct
             where TU : struct
         {
             var arrayPtr = IntPtr.Zero;
-            var count = getRef(nativeRef, arrayPtr);
+            var count = getRef(nativeRef, out arrayPtr);
             if(count == 0)
             {
 #if NETSTANDARD1_1 || NET40
@@ -142,9 +142,10 @@ namespace LibVLCSharp.Shared.Helpers
             return resultList.ToArray();
         }
 
-        internal delegate ulong CategoryArrayRef<T>(IntPtr nativeRef, T enumType, out IntPtr array) where T : Enum;
+        internal delegate ulong CategoryArrayOut<T>(IntPtr nativeRef, T enumType, out IntPtr array) where T : Enum;
+        internal delegate uint ArrayOut(IntPtr nativeRef, out IntPtr array);
 
-        internal static TU[] Retrieve<T, TU, TE>(IntPtr nativeRef, TE extraParam, CategoryArrayRef<TE> getRef, Func<IntPtr, T> retrieve,
+        internal static TU[] Retrieve<T, TU, TE>(IntPtr nativeRef, TE extraParam, CategoryArrayOut<TE> getRef, Func<IntPtr, T> retrieve,
             Func<T, TU> create, Action<IntPtr, ulong> releaseRef) 
             where T : struct
             where TU : struct

LibVLCSharp/Shared/Helpers/Utf8StringMarshaler.cs

@@ -31,14 +31,14 @@ namespace LibVLCSharp.Shared.Helpers
             return ptr;
         }
 
-        public object MarshalNativeToManaged(IntPtr pNativeData)
+        public object MarshalNativeToManaged(IntPtr ptr)
         {
-            if (pNativeData == IntPtr.Zero)
+            if (ptr == IntPtr.Zero)
                 return null;
             List<byte> bytes = new List<byte>();
             for (int offset = 0; ; offset++)
             {
-                byte b = Marshal.ReadByte(pNativeData, offset);
+                byte b = Marshal.ReadByte(ptr, offset);
                 if (b == 0)
                     break;
                 else bytes.Add(b);

LibVLCSharp/Shared/Media.cs

@@ -124,7 +124,7 @@ namespace LibVLCSharp.Shared
 
             [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                 EntryPoint = "libvlc_media_tracks_get")]
-            internal static extern uint LibVLCMediaTracksGet(IntPtr media, ref IntPtr tracksPtr);
+            internal static extern uint LibVLCMediaTracksGet(IntPtr media, out IntPtr tracksPtr);
 
             [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                 EntryPoint = "libvlc_media_tracks_release")]
@@ -148,7 +148,7 @@ namespace LibVLCSharp.Shared
 
             [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                 EntryPoint = "libvlc_media_slaves_get")]
-            internal static extern uint LibVLCMediaGetSlaves(IntPtr media, ref IntPtr slaves);
+            internal static extern uint LibVLCMediaGetSlaves(IntPtr media, out IntPtr slaves);
 
             [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                 EntryPoint = "libvlc_media_slaves_release")]
@@ -559,7 +559,7 @@ namespace LibVLCSharp.Shared
         /// <para>Not doing this will result in an empty array.</para>
         /// <para>LibVLC 2.1.0 and later.</para>
         /// </remarks>
-        public MediaTrack[] Tracks => MarshalUtils.Retrieve(NativeReference, (nativeRef, arrayPtr) => Native.LibVLCMediaTracksGet(nativeRef, ref arrayPtr),
+        public MediaTrack[] Tracks => MarshalUtils.Retrieve(NativeReference, (IntPtr nativeRef, out IntPtr array) => Native.LibVLCMediaTracksGet(nativeRef, out array),
             MarshalUtils.PtrToStructure<MediaTrackStructure>,
             m => m.Build(),
             Native.LibVLCMediaTracksRelease);
@@ -609,10 +609,10 @@ namespace LibVLCSharp.Shared
         /// <para>LibVLC 3.0.0 and later.</para>
         /// <para>libvlc_media_slaves_add</para>
         /// </remarks>
-        public MediaSlave[] Slaves => MarshalUtils.Retrieve(NativeReference, (nativeRef,  arrayPtr) => Native.LibVLCMediaGetSlaves(nativeRef, ref arrayPtr),
-                MarshalUtils.PtrToStructure<MediaSlaveStructure>,
-                s => s.Build(),
-                Native.LibVLCMediaReleaseSlaves);
+        public MediaSlave[] Slaves => MarshalUtils.Retrieve(NativeReference, (IntPtr nativeRef, out IntPtr array) => Native.LibVLCMediaGetSlaves(nativeRef, out array),
+            MarshalUtils.PtrToStructure<MediaSlaveStructure>,
+            s => s.Build(),
+            Native.LibVLCMediaReleaseSlaves);
 
         public override bool Equals(object obj)
         {

LibVLCSharp/Shared/Structures/AudioTrack.cs

-namespace LibVLCSharp.Shared
-{
-    public readonly struct AudioTrack
-    {
-        public readonly uint Channels;
-        public readonly uint Rate;
-    }
-}

LibVLCSharp/Shared/Structures/MediaTrack.cs

@@ -12,12 +12,107 @@ namespace LibVLCSharp.Shared
         internal readonly TrackType TrackType;
         internal readonly int Profile;
         internal readonly int Level;
-        internal readonly MediaTrackData Data;
+        internal readonly IntPtr TrackData;
         internal readonly uint Bitrate;
         internal readonly IntPtr Language;
         internal readonly IntPtr Description;
     }
 
+    internal readonly struct SubtitleTrackStructure
+    {
+        internal readonly IntPtr Encoding;
+    }
+
+    /// <summary>
+    /// Audio track
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public readonly struct AudioTrack
+    {
+        internal AudioTrack(uint channels, uint rate)
+        {
+            Channels = channels;
+            Rate = rate;
+        }
+
+        /// <summary>
+        /// Audio track channels
+        /// </summary>
+        public readonly uint Channels;
+
+        /// <summary>
+        /// Audio track rate
+        /// </summary>
+        public readonly uint Rate;
+    }
+
+    /// <summary>
+    /// Video track
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public readonly struct VideoTrack
+    {
+        /// <summary>
+        /// Video height
+        /// </summary>
+        public readonly uint Height;
+
+        /// <summary>
+        /// Video Width
+        /// </summary>
+        public readonly uint Width;
+
+        /// <summary>
+        /// Video SarNum
+        /// </summary>
+        public readonly uint SarNum;
+
+        /// <summary>
+        /// Video SarDen
+        /// </summary>
+        public readonly uint SarDen;
+
+        /// <summary>
+        /// Video frame rate num
+        /// </summary>
+        public readonly uint FrameRateNum;
+
+        /// <summary>
+        /// Video frame rate den
+        /// </summary>
+        public readonly uint FrameRateDen;
+
+        /// <summary>
+        /// Video orientation
+        /// </summary>
+        public readonly VideoOrientation Orientation;
+
+        /// <summary>
+        /// Video projection
+        /// </summary>
+        public readonly VideoProjection Projection;
+
+        /// <summary>
+        /// Video viewpoint
+        /// </summary>
+        public readonly VideoViewpoint Pose;
+    }
+
+    /// <summary>
+    /// Subtitle track
+    /// </summary>
+    public readonly struct SubtitleTrack
+    {
+        internal SubtitleTrack(string encoding)
+        {
+            Encoding = encoding;
+        }
+        /// <summary>
+        /// Subtitle encoding
+        /// </summary>
+        public readonly string Encoding;
+    }
+
     /// <summary>
     /// Media track information
     /// </summary>

LibVLCSharp/Shared/Structures/MediaTrackData.cs

@@ -5,6 +5,12 @@
     /// </summary>
     public readonly struct MediaTrackData
     {
+        internal MediaTrackData(AudioTrack audio, VideoTrack video, SubtitleTrack subtitle)
+        {
+            Audio = audio;
+            Video = video;
+            Subtitle = subtitle;
+        }
         /// <summary>
         /// Audio track
         /// </summary>
@@ -20,4 +26,4 @@
         /// </summary>
         public readonly SubtitleTrack Subtitle;
     }
-}
+}
\ No newline at end of file

LibVLCSharp/Shared/Structures/SubtitleTrack.cs

-using System;
-
-namespace LibVLCSharp.Shared
-{
-    public readonly struct SubtitleTrack
-    {
-        public readonly IntPtr Encoding;
-    }
-}

LibVLCSharp/Shared/Structures/VideoTrack.cs

-namespace LibVLCSharp.Shared
-{
-    public readonly struct VideoTrack
-    {
-        public readonly uint Height;
-
-        public readonly uint Width;
-
-        public readonly uint SarNum;
-
-        public readonly uint SarDen;
-
-        public readonly uint FrameRateNum;
-
-        public readonly uint FrameRateDen;
-
-        public readonly VideoOrientation Orientation;
-
-        public readonly VideoProjection Projection;
-
-        public readonly VideoViewpoint Pose;
-    }
-}