libvlc: add helper delay function

Author: mfkl

src/LibVLCSharp/Shared/LibVLC.cs

@@ -776,6 +776,13 @@ static void GetLogContext(IntPtr logContext, out string? module, out string? fil
         /// </summary>
         public long Clock => Native.LibVLCClock();
 
+        /// <summary>
+        /// Return the delay (in microseconds) until a certain timestamp.
+        /// </summary>
+        /// <param name="pts">timestamp in microsecond</param>
+        /// <returns>negative if timestamp is in the past, positive if it is in the future</returns>
+        public long Delay(long pts) => pts - Clock;
+
         #region Exit
 
         static readonly InternalExitCallback ExitCallbackHandle = ExitCallback;

src/LibVLCSharp/Shared/MediaPlayer.cs

@@ -2039,7 +2039,7 @@ public delegate uint LibVLCVideoFormatCb(ref IntPtr opaque, IntPtr chroma, ref u
         /// <param name="data">data pointer as passed to libvlc_audio_set_callbacks() [IN]</param>
         /// <param name="samples">pointer to a table of audio samples to play back [IN]</param>
         /// <param name="count">number of audio samples to play back</param>
-        /// <param name="pts">expected play time stamp (see libvlc_delay())</param>
+        /// <param name="pts">expected play time stamp (see <see cref="LibVLC.Delay(long)"/>)</param>
         /// <remarks>
         /// <para>The LibVLC media player decodes and post-processes the audio signal</para>
         /// <para>asynchronously (in an internal thread). Whenever audio samples are ready</para>