Added ability to retrieve bit depth from media streams for lossless encodings (#359)

* Added ability to retrieve bit depth from media streams for lossless encodings

* Shortened sample AIFF file used in tests

FFMpegCore.Test/FFMpegCore.Test.csproj

@@ -27,6 +27,12 @@
     <Content Include="ffmpeg.config.json">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <None Update="Resources\24_bit_fixed.WAV">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="Resources\32_bit_float.WAV">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
     <None Update="Resources\input.webm">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
@@ -81,6 +87,15 @@
     <None Update="Resources\sample.srt">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
+    <None Update="Resources\sample3aiff.aiff">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="Resources\sampleMKV.mkv">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="Resources\sampleVOC.voc">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
 </Project>

FFMpegCore.Test/FFProbeTests.cs

@@ -145,6 +145,9 @@ public async Task Probe_Async_Success()
         {
             var info = await FFProbe.AnalyseAsync(TestResources.Mp4Video);
             Assert.AreEqual(3, info.Duration.Seconds);
+	        Assert.AreEqual(8, info.PrimaryVideoStream.BitDepth);
+            // This video's audio stream is AAC, which is lossy, so bit depth is meaningless.
+            Assert.IsNull(info.PrimaryAudioStream.BitDepth);
         }
 
         [TestMethod, Timeout(10000)]
@@ -153,6 +156,8 @@ public void Probe_Success_FromStream()
             using var stream = File.OpenRead(TestResources.WebmVideo);
             var info = FFProbe.Analyse(stream);
             Assert.AreEqual(3, info.Duration.Seconds);
+            // This video has no audio stream.
+            Assert.IsNull(info.PrimaryAudioStream);
         }
 
         [TestMethod, Timeout(10000)]
@@ -171,16 +176,60 @@ public async Task Probe_Success_Subtitle_Async()
             Assert.AreEqual(1, info.SubtitleStreams.Count);
             Assert.AreEqual(0, info.AudioStreams.Count);
             Assert.AreEqual(0, info.VideoStreams.Count);
+            // BitDepth is meaningless for subtitles
+            Assert.IsNull(info.SubtitleStreams[0].BitDepth);
         }
 
         [TestMethod, Timeout(10000)]
         public async Task Probe_Success_Disposition_Async()
         {
-            var info = await FFProbe.AnalyseAsync(TestResources.Mp4Video);
-            Assert.IsNotNull(info.PrimaryAudioStream);
-            Assert.IsNotNull(info.PrimaryAudioStream.Disposition);
-            Assert.AreEqual(true, info.PrimaryAudioStream.Disposition["default"]);
-            Assert.AreEqual(false, info.PrimaryAudioStream.Disposition["forced"]);
+	        var info = await FFProbe.AnalyseAsync(TestResources.Mp4Video);
+	        Assert.IsNotNull(info.PrimaryAudioStream);
+	        Assert.IsNotNull(info.PrimaryAudioStream.Disposition);
+	        Assert.AreEqual(true, info.PrimaryAudioStream.Disposition["default"]);
+	        Assert.AreEqual(false, info.PrimaryAudioStream.Disposition["forced"]);
+        }
+
+        [TestMethod, Timeout(10000)]
+        public async Task Probe_Success_Mp3AudioBitDepthNull_Async()
+        {
+	        var info = await FFProbe.AnalyseAsync(TestResources.Mp3Audio);
+	        Assert.IsNotNull(info.PrimaryAudioStream);
+	        // mp3 is lossy, so bit depth is meaningless.
+	        Assert.IsNull(info.PrimaryAudioStream.BitDepth);
+        }
+
+        [TestMethod, Timeout(10000)]
+        public async Task Probe_Success_VocAudioBitDepth_Async()
+        {
+	        var info = await FFProbe.AnalyseAsync(TestResources.AiffAudio);
+	        Assert.IsNotNull(info.PrimaryAudioStream);
+	        Assert.AreEqual(16, info.PrimaryAudioStream.BitDepth);
+        }
+
+        [TestMethod, Timeout(10000)]
+        public async Task Probe_Success_MkvVideoBitDepth_Async()
+        {
+	        var info = await FFProbe.AnalyseAsync(TestResources.MkvVideo);
+	        Assert.IsNotNull(info.PrimaryAudioStream);
+	        Assert.AreEqual(8, info.PrimaryVideoStream.BitDepth);
+	        Assert.IsNull(info.PrimaryAudioStream.BitDepth);
+        }
+
+        [TestMethod, Timeout(10000)]
+        public async Task Probe_Success_24BitWavBitDepth_Async()
+        {
+	        var info = await FFProbe.AnalyseAsync(TestResources.Wav24Bit);
+	        Assert.IsNotNull(info.PrimaryAudioStream);
+	        Assert.AreEqual(24, info.PrimaryAudioStream.BitDepth);
+        }
+
+        [TestMethod, Timeout(10000)]
+        public async Task Probe_Success_32BitWavBitDepth_Async()
+        {
+	        var info = await FFProbe.AnalyseAsync(TestResources.Wav32Bit);
+	        Assert.IsNotNull(info.PrimaryAudioStream);
+	        Assert.AreEqual(32, info.PrimaryAudioStream.BitDepth);
         }
     }
 }

FFMpegCore.Test/Resources/TestResources.cs

@@ -21,5 +21,9 @@ public static class TestResources
         public static readonly string PngImage = "./Resources/cover.png";
         public static readonly string ImageCollection = "./Resources/images";
         public static readonly string SrtSubtitle = "./Resources/sample.srt";
+        public static readonly string AiffAudio = "./Resources/sample3aiff.aiff";
+        public static readonly string MkvVideo = "./Resources/sampleMKV.mkv";
+        public static readonly string Wav24Bit = "./Resources/24_bit_fixed.WAV";
+        public static readonly string Wav32Bit = "./Resources/32_bit_float.WAV";
     }
 }

FFMpegCore/FFProbe/FFProbeAnalysis.cs

@@ -26,6 +26,9 @@ public class FFProbeStream : ITagsContainer, IDispositionContainer
         [JsonPropertyName("bits_per_raw_sample")]
         public string BitsPerRawSample { get; set; } = null!;
         
+        [JsonPropertyName("bits_per_sample")]
+        public int BitsPerSample { get; set; } = 0;
+        
         [JsonPropertyName("bit_rate")]
         public string BitRate { get; set; } = null!;
 

FFMpegCore/FFProbe/MediaAnalysis.cs

@@ -48,6 +48,13 @@ private MediaFormat ParseFormat(Format analysisFormat)
         public List<SubtitleStream> SubtitleStreams { get; }
         public IReadOnlyList<string> ErrorData { get; }
         
+        private int? GetBitDepth(FFProbeStream stream)
+        {
+	        var bitDepth = int.TryParse(stream.BitsPerRawSample, out var bprs) ? bprs :
+		        stream.BitsPerSample;
+	        return bitDepth == 0 ? null : (int?)bitDepth;
+        }
+
         private VideoStream ParseVideoStream(FFProbeStream stream)
         {
             return new VideoStream
@@ -72,12 +79,13 @@ private VideoStream ParseVideoStream(FFProbeStream stream)
                 Language = stream.GetLanguage(),
                 Disposition = MediaAnalysisUtils.FormatDisposition(stream.Disposition),
                 Tags = stream.Tags.ToCaseInsensitive(),
+                BitDepth = GetBitDepth(stream),
             };
         }
 
         private AudioStream ParseAudioStream(FFProbeStream stream)
         {
-            return new AudioStream
+			return new AudioStream
             {
                 Index = stream.Index,
                 BitRate = !string.IsNullOrEmpty(stream.BitRate) ? MediaAnalysisUtils.ParseLongInvariant(stream.BitRate) : default,
@@ -93,6 +101,7 @@ private AudioStream ParseAudioStream(FFProbeStream stream)
                 Language = stream.GetLanguage(),
                 Disposition = MediaAnalysisUtils.FormatDisposition(stream.Disposition),
                 Tags = stream.Tags.ToCaseInsensitive(),
+                BitDepth = GetBitDepth(stream),
             };
         }
 

FFMpegCore/FFProbe/MediaStream.cs

@@ -17,6 +17,7 @@ public abstract class MediaStream
         public string? Language { get; set; }
         public Dictionary<string, bool>? Disposition { get; set; }
         public Dictionary<string, string>? Tags { get; set; }
+        public int? BitDepth { get; set; }
         
         public Codec GetCodecInfo() => FFMpeg.GetCodec(CodecName);
     }