Allow passing custom environment variables to FFmpeg

YoutubeExplode.Converter.Tests/EnvironmentSpecs.cs

@@ -0,0 +1,48 @@
+using System.IO;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Xunit;
+using Xunit.Abstractions;
+using YoutubeExplode.Converter.Tests.Utils;
+
+namespace YoutubeExplode.Converter.Tests;
+
+public class EnvironmentSpecs(ITestOutputHelper testOutput) : IAsyncLifetime
+{
+    public async Task InitializeAsync() => await FFmpeg.InitializeAsync();
+
+    public Task DisposeAsync() => Task.CompletedTask;
+
+    [Fact]
+    public async Task I_can_download_a_video_with_custom_environment_variables_passed_to_FFmpeg()
+    {
+        // Arrange
+        var youtube = new YoutubeClient();
+
+        using var dir = TempDir.Create();
+        var filePath = Path.Combine(dir.Path, "video.mp4");
+
+        var logFilePath = Path.Combine(dir.Path, "ffreport.log");
+
+        // FFREPORT file path must be relative to the current working directory
+        var logFilePathFormatted = Path.GetRelativePath(
+                Directory.GetCurrentDirectory(),
+                logFilePath
+            )
+            .Replace('\\', '/');
+
+        // Act
+        await youtube.Videos.DownloadAsync(
+            "9bZkp7q19f0",
+            filePath,
+            o =>
+                o.SetFFmpegPath(FFmpeg.FilePath)
+                    .SetEnvironmentVariable("FFREPORT", $"file={logFilePathFormatted}:level=32")
+        );
+
+        // Assert
+        File.Exists(logFilePath).Should().BeTrue();
+
+        testOutput.WriteLine(await File.ReadAllTextAsync(logFilePath));
+    }
+}

YoutubeExplode.Converter.Tests/GeneralSpecs.cs

@@ -199,7 +199,7 @@ await youtube.Videos.DownloadAsync(
     }
 
     [Fact]
-    public async Task I_can_download_a_video_using_custom_conversion_settings()
+    public async Task I_can_download_a_video_with_custom_conversion_settings()
     {
         // Arrange
         var youtube = new YoutubeClient();

YoutubeExplode.Converter/ConversionExtensions.cs

@@ -79,7 +79,7 @@ public static async ValueTask DownloadAsync(
         CancellationToken cancellationToken = default
     )
     {
-        var ffmpeg = new FFmpeg(request.FFmpegCliFilePath);
+        var ffmpeg = new FFmpeg(request.FFmpegCliFilePath, request.EnvironmentVariables);
         var converter = new Converter(videoClient, ffmpeg, request.Preset);
 
         await converter.ProcessAsync(

YoutubeExplode.Converter/ConversionRequest.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using YoutubeExplode.Videos.Streams;
 
@@ -11,7 +12,8 @@ public class ConversionRequest(
     string ffmpegCliFilePath,
     string outputFilePath,
     Container container,
-    ConversionPreset preset
+    ConversionPreset preset,
+    IReadOnlyDictionary<string, string?> environmentVariables
 )
 {
     /// <summary>
@@ -24,7 +26,13 @@ public ConversionRequest(
         ConversionFormat format,
         ConversionPreset preset
     )
-        : this(ffmpegCliFilePath, outputFilePath, new Container(format.Name), preset) { }
+        : this(
+            ffmpegCliFilePath,
+            outputFilePath,
+            new Container(format.Name),
+            preset,
+            new Dictionary<string, string?>()
+        ) { }
 
     /// <summary>
     /// Path to the FFmpeg CLI.
@@ -51,4 +59,10 @@ ConversionPreset preset
     /// Encoder preset.
     /// </summary>
     public ConversionPreset Preset { get; } = preset;
+
+    /// <summary>
+    /// Environment variables to set for the FFmpeg process.
+    /// </summary>
+    public IReadOnlyDictionary<string, string?> EnvironmentVariables { get; } =
+        environmentVariables;
 }

YoutubeExplode.Converter/ConversionRequestBuilder.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using YoutubeExplode.Converter.Utils.Extensions;
@@ -11,6 +12,10 @@ namespace YoutubeExplode.Converter;
 /// </summary>
 public class ConversionRequestBuilder(string outputFilePath)
 {
+    private readonly Dictionary<string, string?> _environmentVariables = new(
+        StringComparer.Ordinal
+    );
+
     private string? _ffmpegCliFilePath;
     private Container? _container;
     private ConversionPreset _preset;
@@ -64,6 +69,15 @@ public ConversionRequestBuilder SetPreset(ConversionPreset preset)
         return this;
     }
 
+    /// <summary>
+    /// Sets an environment variable for the FFmpeg process.
+    /// </summary>
+    public ConversionRequestBuilder SetEnvironmentVariable(string name, string? value)
+    {
+        _environmentVariables[name] = value;
+        return this;
+    }
+
     /// <summary>
     /// Builds the resulting request.
     /// </summary>
@@ -72,6 +86,7 @@ public ConversionRequest Build() =>
             _ffmpegCliFilePath ?? FFmpeg.GetFilePath(),
             outputFilePath,
             _container ?? GetDefaultContainer(),
-            _preset
+            _preset,
+            _environmentVariables
         );
 }

YoutubeExplode.Converter/FFmpeg.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Linq;
@@ -13,9 +14,12 @@
 namespace YoutubeExplode.Converter;
 
 // Ideally this should use named pipes and stream through stdout.
-// However, named pipes aren't well supported on non-Windows OS and
+// However, named pipes aren't well-supported on non-Windows OS and
 // stdout streaming only works with some specific formats.
-internal partial class FFmpeg(string filePath)
+internal partial class FFmpeg(
+    string filePath,
+    IReadOnlyDictionary<string, string?> environmentVariables
+)
 {
     public async ValueTask ExecuteAsync(
         string arguments,
@@ -36,6 +40,7 @@ public async ValueTask ExecuteAsync(
         {
             await Cli.Wrap(filePath)
                 .WithArguments(arguments)
+                .WithEnvironmentVariables(environmentVariables)
                 .WithStandardErrorPipe(stdErrPipe)
                 .ExecuteAsync(cancellationToken);
         }

YoutubeExplode.Tests/StreamSpecs.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Buffers;
 using System.IO;
 using System.Linq;