Enhance audio source interface and project configurations

- Added new using directives and an event for handling encoded audio samples in `MediaEndPoints.cs`.
- Updated `SIPSorceryMedia.Abstractions.csproj` to set the language version to 12.0.
- Modified `SIPSorceryMedia.Abstractions.UnitTest.csproj` to support multi-targeting for `net462` and `net8.0`, with conditional xUnit runner package references based on the target framework.

Author: Paulo Morgado

src/MediaEndPoints.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Net;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
@@ -164,7 +166,7 @@ public struct AudioFormat
         public const int DEFAULT_CHANNEL_COUNT = 1;
 
         public static readonly AudioFormat Empty = new AudioFormat()
-            { _isNonEmpty = false, ClockRate = DEFAULT_CLOCK_RATE, ChannelCount = DEFAULT_CHANNEL_COUNT };
+        { _isNonEmpty = false, ClockRate = DEFAULT_CLOCK_RATE, ChannelCount = DEFAULT_CHANNEL_COUNT };
 
         public AudioCodecsEnum Codec { get; set; }
 
@@ -288,7 +290,7 @@ public AudioFormat(int formatID, string formatName, int clockRate, int rtpClockR
             {
                 throw new ApplicationException($"The format name must be provided for an AudioFormat.");
             }
-            else if(clockRate <= 0)
+            else if (clockRate <= 0)
             {
                 throw new ApplicationException($"The clock rate for an AudioFormat must be greater than 0.");
             }
@@ -329,7 +331,7 @@ public struct VideoFormat
         public const int DEFAULT_CLOCK_RATE = 90000;
 
         public static readonly VideoFormat Empty = new VideoFormat()
-            { _isNonEmpty = false, ClockRate = DEFAULT_CLOCK_RATE };
+        { _isNonEmpty = false, ClockRate = DEFAULT_CLOCK_RATE };
 
         public VideoCodecsEnum Codec { get; set; }
 
@@ -544,6 +546,14 @@ public interface IAudioEncoder
         /// <returns>A byte array containing the encoded sample.</returns>
         byte[] EncodeAudio(short[] pcm, AudioFormat format);
 
+        /// <summary>
+        /// Encodes 16bit signed PCM samples.
+        /// </summary>
+        /// <param name="pcm">An array of 16 bit signed audio samples.</param>
+        /// <param name="format">The audio format to encode the PCM sample to.</param>
+        /// <param name="destination">A <see cref="IBufferWriter{T}"/> of <see langword="byte"/> to receieve the encoded sample.</param>
+        void EncodeAudio(ReadOnlySpan<short> pcm, AudioFormat format, IBufferWriter<byte> destination);
+
         /// <summary>
         /// Decodes to 16bit signed PCM samples.
         /// </summary>
@@ -649,6 +659,8 @@ public interface IAudioSource
     {
         event EncodedSampleDelegate OnAudioSourceEncodedSample;
 
+        event Action<uint, ReadOnlyMemory<byte>> OnAudioSourceEncodedSampleEx;
+
         event RawAudioSampleDelegate OnAudioSourceRawSample;
 
         event SourceErrorDelegate OnAudioSourceError;

src/SIPSorceryMedia.Abstractions.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <PackageId>SIPSorceryMedia.Abstractions</PackageId>
     <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1;net5.0;net8.0</TargetFrameworks>
+    <LangVersion>12.0</LangVersion>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <!-- Disable warning for missing XML doc comments. -->

test/SIPSorceryMedia.Abstractions.UnitTest/SIPSorceryMedia.Abstractions.UnitTest.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8</TargetFramework>
+    <TargetFrameworks>net462;net8.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
@@ -11,10 +11,6 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageReference Include="System.Drawing.Common" Version="9.0.0" />
     <PackageReference Include="xunit" Version="2.9.2" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="3.0.0">
-      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
-      <PrivateAssets>all</PrivateAssets>
-    </PackageReference>
     <PackageReference Include="coverlet.collector" Version="6.0.3">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
@@ -24,6 +20,20 @@
     <PackageReference Include="Serilog.Sinks.XUnit" Version="3.0.19" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFramework)' == 'net462'">
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.0.0">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\..\src\SIPSorceryMedia.Abstractions.csproj" />
   </ItemGroup>