Small perf fixes and some code reuse

MetadataExtractor/Formats/Jpeg/JpegSegmentType.cs

@@ -222,7 +222,7 @@ public static bool CanContainMetadata(this JpegSegmentType type)
 
         /// <summary>Gets JPEG segment types that might contain metadata.</summary>
 #if NET5_0_OR_GREATER
-        public static IReadOnlyList<JpegSegmentType> CanContainMetadataTypes { get; } = Enum.GetValues<JpegSegmentType>().Cast<JpegSegmentType>().Where(type => type.CanContainMetadata()).ToList();
+        public static IReadOnlyList<JpegSegmentType> CanContainMetadataTypes { get; } = Enum.GetValues<JpegSegmentType>().Where(type => type.CanContainMetadata()).ToList();
 #else
         public static IReadOnlyList<JpegSegmentType> CanContainMetadataTypes { get; } = Enum.GetValues(typeof(JpegSegmentType)).Cast<JpegSegmentType>().Where(type => type.CanContainMetadata()).ToList();
 #endif

MetadataExtractor/Formats/QuickTime/QuickTimeMetadataReader.cs

@@ -263,8 +263,9 @@ void MoovHandler(AtomCallbackArgs a)
                     case "uuid":
                     {
                         ReadOnlySpan<byte> cr3 = [0x85, 0xc0, 0xb6, 0x87, 0x82, 0x0f, 0x11, 0xe0, 0x81, 0x11, 0xf4, 0xce, 0x46, 0x2b, 0x6a, 0x48];
-                        var uuid = a.Reader.GetBytes(cr3.Length);
-                        if (cr3.SequenceEqual(uuid))
+                        Span<byte> actual = stackalloc byte[cr3.Length];
+                        a.Reader.GetBytes(actual);
+                        if (cr3.SequenceEqual(actual))
                         {
                             QuickTimeReader.ProcessAtoms(stream, UuidHandler, a.BytesLeft);
                         }

MetadataExtractor/Formats/QuickTime/QuickTimeReader.cs

@@ -1,5 +1,7 @@
 // Copyright (c) Drew Noakes and contributors. All Rights Reserved. Licensed under the Apache License, Version 2.0. See LICENSE in the project root for license information.
 
+using MetadataExtractor.Formats.Iso14496;
+
 namespace MetadataExtractor.Formats.QuickTime
 {
     /// <summary>
@@ -43,19 +45,7 @@ public sealed class AtomCallbackArgs(uint type, long size, Stream stream, long s
         /// <summary>
         /// Gets the string representation of this atom's type.
         /// </summary>
-        public string TypeString
-        {
-            get
-            {
-                var bytes = BitConverter.GetBytes(Type);
-                Array.Reverse(bytes);
-#if NETSTANDARD1_3
-                return Encoding.UTF8.GetString(bytes);
-#else
-                return Encoding.ASCII.GetString(bytes);
-#endif
-            }
-        }
+        public string TypeString => TypeStringConverter.ToTypeString(Type);
 
         /// <summary>
         /// Computes the number of bytes remaining in the atom, given the <see cref="Stream"/> position.

MetadataExtractor/Formats/QuickTime/QuickTimeReaderExtensions.cs

@@ -16,15 +16,17 @@ public static string Get4ccString(this SequentialReader reader)
             // https://en.wikipedia.org/wiki/FourCC
 
             Span<byte> bytes = stackalloc byte[4];
-            Span<char> chars = stackalloc char[4];
 
             reader.GetBytes(bytes);
 
             // NOTE we cannot just use Encoding.ASCII here, as that can replace certain non-printable characters with '?'
-            chars[0] = (char)bytes[0];
-            chars[1] = (char)bytes[1];
-            chars[2] = (char)bytes[2];
-            chars[3] = (char)bytes[3];
+            Span<char> chars =
+            [
+                (char)bytes[0],
+                (char)bytes[1],
+                (char)bytes[2],
+                (char)bytes[3]
+            ];
 
 #if NET462 || NETSTANDARD1_3
             fixed (char* pChars = chars)