partial v4l2m2m accel support (#2416)

* start to add v4l2m2m accel

* add v4l2m2m pipeline

* add encoders

* fix decoders and encoders

* output software frames from decoders

* more buffers

* hide v4l2m2m from ui

ErsatzTV/Validators/FFmpegProfileEditViewModelValidator.cs

@@ -40,6 +40,11 @@ public class FFmpegProfileEditViewModelValidator : AbstractValidator<FFmpegProfi
         FFmpegProfileVideoFormat.Hevc
     ];
 
+    private static readonly List<FFmpegProfileVideoFormat> V4l2m2mFormats =
+    [
+        FFmpegProfileVideoFormat.H264,
+        FFmpegProfileVideoFormat.Hevc
+    ];
     public FFmpegProfileEditViewModelValidator()
     {
         RuleFor(x => x.Name).NotEmpty();
@@ -93,6 +98,14 @@ public class FFmpegProfileEditViewModelValidator : AbstractValidator<FFmpegProfi
                     .WithMessage("Amf supports formats (h264, hevc)");
             });
 
+        When(
+            x => x.HardwareAcceleration == HardwareAccelerationKind.V4l2m2m,
+            () =>
+            {
+                RuleFor(x => x.VideoFormat).Must(c => V4l2m2mFormats.Contains(c))
+                    .WithMessage("V4L2 M2M supports formats (h264, hevc)");
+            });
+
         When(
             x => x.VideoFormat == FFmpegProfileVideoFormat.Mpeg2Video,
             () => RuleFor(x => x.BitDepth)