properly specify audio codec even when source has correct format (#641)

ErsatzTV.Core.Tests/FFmpeg/TranscodingTests.cs

@@ -271,7 +271,8 @@ namespace ErsatzTV.Core.Tests.FFmpeg
                     FFmpegProfile = FFmpegProfile.New("test", profileResolution) with
                     {
                         HardwareAcceleration = profileAcceleration,
-                        VideoCodec = profileCodec
+                        VideoCodec = profileCodec,
+                        AudioCodec = "aac"
                     },
                     StreamingMode = StreamingMode.TransportStream
                 },

ErsatzTV.FFmpeg/PipelineBuilder.cs

@@ -360,12 +360,9 @@ public class PipelineBuilder
             {
                 _pipelineSteps.Add(new EncoderCopyAudio());
             }
-            
-            // TODO: while?
-            if (!IsDesiredAudioState(currentState, desiredState))
-            {
-                if (currentState.AudioFormat != desiredState.AudioFormat)
+            else
             {
+                // always need to specify audio codec so ffmpeg doesn't default to a codec we don't want
                 foreach (IEncoder step in AvailableEncoders.ForAudioFormat(desiredState, _logger))
                 {
                     currentState = step.NextState(currentState);
@@ -373,6 +370,9 @@ public class PipelineBuilder
                 }
             }
 
+            // TODO: while?
+            if (!IsDesiredAudioState(currentState, desiredState))
+            {
                 foreach (int desiredAudioChannels in desiredState.AudioChannels)
                 {
                     if (currentState.AudioChannels != desiredAudioChannels)