feat: extract audio conversion to separate class and refine audio extraction

src/StreamShorts.Console/Commands/DefaultCommand.cs

@@ -3,12 +3,14 @@ namespace StreamShorts.Console.Commands;
 internal class DefaultCommand(
   IFileSystem fileSystem,
   IAnsiConsole console,
-  IAudioExtractor audioExtractor
+  IAudioExtractor audioExtractor,
+  IAudioConverter audioConverter
 ) : AsyncCommand<DefaultCommand.Settings>
 {
   private readonly IFileSystem _fileSystem = fileSystem ?? throw new ArgumentNullException(nameof(fileSystem));
   private readonly IAnsiConsole _console = console ?? throw new ArgumentNullException(nameof(console));
   private readonly IAudioExtractor _audioExtractor = audioExtractor ?? throw new ArgumentNullException(nameof(audioExtractor));
+  private readonly IAudioConverter _audioConverter = audioConverter ?? throw new ArgumentNullException(nameof(audioConverter));
 
   internal class Settings : CommandSettings
   {
@@ -61,6 +63,23 @@ internal class DefaultCommand(
 
     _console.MarkupLine($"[blue]Audio extracted[/] [green]successfully![/]");
 
+    Stream? wavStream = null;
+
+    _console.Status()
+      .Spinner(Spinner.Known.Dots)
+      .Start("Converting audio...", ctx =>
+      {
+        wavStream = _audioConverter.ConvertMp3ToWav16(audioStream);
+      });
+
+    if (wavStream is null)
+    {
+      _console.MarkupLine("[red]Failed[/] to convert audio to WAV format.");
+      return 2;
+    }
+
+    _console.MarkupLine($"[blue]Audio converted[/] [green]successfully![/]");
+
     return 0;
   }
 }

src/StreamShorts.Console/Program.cs

@@ -37,6 +37,7 @@ try
       services.AddSingleton(AnsiConsole.Console);
       services.AddSingleton<IFileSystem, FileSystem>();
       services.AddSingleton<IAudioExtractor, AudioExtractor>();
+      services.AddSingleton<IAudioConverter, AudioConverter>();
     })
     .BuildApp()
     .RunAsync(args);
@@ -53,25 +54,6 @@ finally
   await Log.CloseAndFlushAsync();
 }
 
-// using var mp3Stream = new MemoryStream();
-// using var mp4Stream = new FileStream(args[0], FileMode.Open, FileAccess.Read);
-
-// var wasExtracted = await FFMpegArguments
-//   .FromPipeInput(new StreamPipeSource(mp4Stream))
-//   .OutputToPipe(
-//     new StreamPipeSink(mp3Stream),
-//     o => o.DisableChannel(Channel.Video).ForceFormat("mp3")
-//   )
-//   .ProcessAsynchronously();
-
-// // Step 2: Convert MP3 stream to 16khz wave format
-// mp3Stream.Position = 0;
-// using var reader = new Mp3FileReader(mp3Stream);
-// var outFormat = new WaveFormat(16000, reader.WaveFormat.Channels);
-// using var resampler = new MediaFoundationResampler(reader, outFormat);
-// using var waveStream = new MemoryStream();
-// WaveFileWriter.WriteWavFileToStream(waveStream, resampler);
-
 // // Step 3: Split the wave stream into 2 minute segments
 // waveStream.Position = 0;
 // var segmentDuration = TimeSpan.FromMinutes(2);

src/StreamShorts.Library/Media/Audio/AudioConverter.cs

@@ -0,0 +1,18 @@
+
+using NAudio.Wave;
+
+namespace StreamShorts.Library.Media.Audio;
+
+public class AudioConverter : IAudioConverter
+{
+  public Stream ConvertMp3ToWav16(Stream mp3)
+  {
+    using var reader = new Mp3FileReader(mp3);
+    var outFormat = new WaveFormat(16000, reader.WaveFormat.Channels);
+    using var resampler = new MediaFoundationResampler(reader, outFormat);
+    var waveStream = new MemoryStream();
+    WaveFileWriter.WriteWavFileToStream(waveStream, resampler);
+    waveStream.Position = 0;
+    return waveStream;
+  }
+}

src/StreamShorts.Library/Media/Audio/AudioExtractor.cs

@@ -1,13 +1,19 @@
-using FFMpegCore;
-using FFMpegCore.Pipes;
-
-using Channel = FFMpegCore.Enums.Channel;
-
 namespace StreamShorts.Library.Media.Audio;
 
 /// <inheritdoc/>
 public class AudioExtractor : IAudioExtractor
 {
+  private readonly IFFMpegService _ffmpegService = new FFMpegService();
+
+  public AudioExtractor()
+  {
+  }
+
+  internal AudioExtractor(IFFMpegService ffmpegService)
+  {
+    _ffmpegService = ffmpegService;
+  }
+
   public async Task<Stream> ExtractMp3FromMp4Async(Stream video)
   {
     if (video is null)
@@ -29,26 +35,20 @@ public class AudioExtractor : IAudioExtractor
 
     try
     {
-      using var mp3Stream = new MemoryStream();
+      var mp3Stream = new MemoryStream();
       using var mp4Stream = new MemoryStream();
 
       await video.CopyToAsync(mp4Stream).ConfigureAwait(false);
       mp4Stream.Position = 0;
 
-      var wasExtracted = await FFMpegArguments
-        .FromPipeInput(new StreamPipeSource(mp4Stream))
-        .OutputToPipe(
-          new StreamPipeSink(mp3Stream),
-          o => o.DisableChannel(Channel.Video).ForceFormat("mp3")
-        )
-        .ProcessAsynchronously()
-        .ConfigureAwait(false);
+      var wasExtracted = await _ffmpegService.ExtractAudioFromVideoAsync(mp4Stream, mp3Stream).ConfigureAwait(false);
 
       if (wasExtracted is false)
       {
         throw new FailedAudioExtractionException("Failed to extract audio from the video stream.");
       }
 
+      mp3Stream.Position = 0;
       return mp3Stream;
     }
     catch (Exception e) when (e is not FailedAudioExtractionException)

src/StreamShorts.Library/Media/Audio/IAudioConverter.cs

@@ -0,0 +1,6 @@
+namespace StreamShorts.Library.Media.Audio;
+
+public interface IAudioConverter
+{
+  Stream ConvertMp3ToWav16(Stream mp3);
+}

src/StreamShorts.Library/Media/FFMpegService.cs

@@ -0,0 +1,23 @@
+using System.Diagnostics.CodeAnalysis;
+
+using FFMpegCore;
+using FFMpegCore.Enums;
+using FFMpegCore.Pipes;
+
+namespace StreamShorts.Library.Media;
+
+[ExcludeFromCodeCoverage]
+internal class FFMpegService : IFFMpegService
+{
+  public async Task<bool> ExtractAudioFromVideoAsync(Stream video, Stream audio)
+  {
+    return await FFMpegArguments
+      .FromPipeInput(new StreamPipeSource(video))
+      .OutputToPipe(
+        new StreamPipeSink(audio),
+        static o => o.DisableChannel(Channel.Video).ForceFormat("mp3")
+      )
+      .ProcessAsynchronously()
+      .ConfigureAwait(false);
+  }
+}

src/StreamShorts.Library/Media/IFFMpegService.cs

@@ -0,0 +1,6 @@
+namespace StreamShorts.Library.Media;
+
+internal interface IFFMpegService
+{
+  Task<bool> ExtractAudioFromVideoAsync(Stream video, Stream audio);
+}

src/StreamShorts.Library/StreamShorts.Library.csproj

@@ -1,5 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <ItemGroup>
     <PackageReference Include="FFMpegCore" />
+    <PackageReference Include="NAudio" />
   </ItemGroup>
 </Project>

tests/StreamShorts.Library.Tests/Unit/Media/Audio/AudioConverterTests.cs

@@ -0,0 +1,10 @@
+namespace StreamShorts.Library.Tests.Unit.Media.Audio;
+
+public class AudioConverterTests
+{
+  [Fact]
+  public void Test()
+  {
+    throw new NotImplementedException();
+  }
+}

tests/StreamShorts.Library.Tests/Unit/Media/Audio/AudioExtractorTests.cs

@@ -1,8 +1,18 @@
+using System.Text;
+
+using StreamShorts.Library.Media;
+
 namespace StreamShorts.Library.Tests.Unit.Media.Audio;
 
 public class AudioExtractorTests
 {
-  private readonly AudioExtractor _sut = new();
+  private readonly Mock<IFFMpegService> _mockFfmpegService = new();
+  private readonly AudioExtractor _sut;
+
+  public AudioExtractorTests()
+  {
+    _sut = new(_mockFfmpegService.Object);
+  }
 
   [Fact]
   public async Task ExtractMp3FromMp4Async_WhenVideoIsNull_ItShouldThrow()
@@ -33,4 +43,93 @@ public class AudioExtractorTests
 
     await action.Should().ThrowAsync<ArgumentException>();
   }
+
+  [Fact]
+  public async Task ExtractMp3FromMp4Async_WhenFFMpegServiceThrows_ItShouldThrow()
+  {
+    var mockStream = new Mock<Stream>();
+    mockStream.Setup(static s => s.CanRead).Returns(true);
+    mockStream.Setup(static s => s.CanSeek).Returns(true);
+
+    _mockFfmpegService.
+      Setup(
+        static m => m.ExtractAudioFromVideoAsync(
+          It.IsAny<Stream>(),
+          It.IsAny<Stream>()
+        )
+      )
+      .ThrowsAsync(new Exception());
+
+    var action = async () => await _sut.ExtractMp3FromMp4Async(mockStream.Object);
+
+    await action.Should().ThrowAsync<FailedAudioExtractionException>();
+  }
+
+  [Fact]
+  public async Task ExtractMp3FromMp4Async_WhenFFMpegServiceFailsExtraction_ItShouldThrow()
+  {
+    var mockStream = new Mock<Stream>();
+    mockStream.Setup(static s => s.CanRead).Returns(true);
+    mockStream.Setup(static s => s.CanSeek).Returns(true);
+
+    _mockFfmpegService.
+      Setup(
+        static m => m.ExtractAudioFromVideoAsync(
+          It.IsAny<Stream>(),
+          It.IsAny<Stream>()
+        )
+      )
+      .ReturnsAsync(false);
+
+    var action = async () => await _sut.ExtractMp3FromMp4Async(mockStream.Object);
+
+    await action.Should().ThrowAsync<FailedAudioExtractionException>();
+  }
+
+  [Fact]
+  public async Task ExtractMp3FromMp4Async_WhenFFMpegServiceSucceedsAtExtractingAudio_ItShouldReturnStream()
+  {
+    var mockStream = new Mock<Stream>();
+    mockStream.Setup(static s => s.CanRead).Returns(true);
+    mockStream.Setup(static s => s.CanSeek).Returns(true);
+
+    _mockFfmpegService.
+      Setup(
+        static m => m.ExtractAudioFromVideoAsync(
+          It.IsAny<Stream>(),
+          It.IsAny<Stream>()
+        )
+      )
+      .ReturnsAsync(true);
+
+    var result = await _sut.ExtractMp3FromMp4Async(mockStream.Object);
+
+    result.Should().BeAssignableTo<Stream>();
+    result.Should().BeOfType<MemoryStream>();
+  }
+
+  [Fact]
+  public async Task ExtractMp3FromMp4Async_WhenCalled_ItShouldNotMutatePositionOfPassedStream()
+  {
+    var text = "hello world";
+    var textByte = Encoding.UTF8.GetBytes(text);
+    var stream = new MemoryStream(textByte);
+
+    var positionToRead = 5;
+    var buffer = new byte[5];
+    await stream.ReadAsync(buffer.AsMemory(0, positionToRead), TestContext.Current.CancellationToken);
+
+    _mockFfmpegService.
+      Setup(
+        static m => m.ExtractAudioFromVideoAsync(
+          It.IsAny<Stream>(),
+          It.IsAny<Stream>()
+        )
+      )
+      .ReturnsAsync(true);
+
+    await _sut.ExtractMp3FromMp4Async(stream);
+
+    stream.Position.Should().Be(positionToRead);
+  }
 }