diff --git a/extensions/cronet/src/main/java/com/google/android/exoplayer2/ext/cronet/CronetDataSource.java b/extensions/cronet/src/main/java/com/google/android/exoplayer2/ext/cronet/CronetDataSource.java
index e15c5180aa..178b7c03cf 100644
--- a/extensions/cronet/src/main/java/com/google/android/exoplayer2/ext/cronet/CronetDataSource.java
+++ b/extensions/cronet/src/main/java/com/google/android/exoplayer2/ext/cronet/CronetDataSource.java
@@ -35,6 +35,7 @@ import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Clock;
 import com.google.android.exoplayer2.util.ConditionVariable;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import com.google.common.base.Predicate;
 import com.google.common.net.HttpHeaders;
 import com.google.common.primitives.Ints;
@@ -546,8 +547,7 @@ public class CronetDataSource extends BaseDataSource implements HttpDataSource {
       @Nullable IOException connectionOpenException = exception;
       if (connectionOpenException != null) {
         @Nullable String message = connectionOpenException.getMessage();
-        if (message != null
-            && Util.toLowerInvariant(message).contains("err_cleartext_not_permitted")) {
+        if (message != null && Ascii.toLowerCase(message).contains("err_cleartext_not_permitted")) {
           throw new CleartextNotPermittedException(connectionOpenException, dataSpec);
         }
         throw new OpenException(connectionOpenException, dataSpec, getStatus(urlRequest));
diff --git a/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java b/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java
index c2dadc4521..0b881955a1 100644
--- a/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java
+++ b/extensions/okhttp/src/main/java/com/google/android/exoplayer2/ext/okhttp/OkHttpDataSource.java
@@ -32,6 +32,7 @@ import com.google.android.exoplayer2.upstream.HttpUtil;
 import com.google.android.exoplayer2.upstream.TransferListener;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import com.google.common.base.Predicate;
 import com.google.common.net.HttpHeaders;
 import java.io.IOException;
@@ -289,7 +290,7 @@ public class OkHttpDataSource extends BaseDataSource implements HttpDataSource {
     } catch (IOException e) {
       @Nullable String message = e.getMessage();
       if (message != null
-          && Util.toLowerInvariant(message).matches("cleartext communication.*not permitted.*")) {
+          && Ascii.toLowerCase(message).matches("cleartext communication.*not permitted.*")) {
         throw new CleartextNotPermittedException(e, dataSpec);
       }
       throw new HttpDataSourceException(
diff --git a/library/common/src/main/java/com/google/android/exoplayer2/metadata/id3/Id3Decoder.java b/library/common/src/main/java/com/google/android/exoplayer2/metadata/id3/Id3Decoder.java
index f660e21bfd..5bd0e1e3e8 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/metadata/id3/Id3Decoder.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/metadata/id3/Id3Decoder.java
@@ -24,6 +24,7 @@ import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.ParsableBitArray;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import java.io.UnsupportedEncodingException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
@@ -539,13 +540,13 @@ public final class Id3Decoder extends SimpleMetadataDecoder {
     int mimeTypeEndIndex;
     if (majorVersion == 2) {
       mimeTypeEndIndex = 2;
-      mimeType = "image/" + Util.toLowerInvariant(new String(data, 0, 3, "ISO-8859-1"));
+      mimeType = "image/" + Ascii.toLowerCase(new String(data, 0, 3, "ISO-8859-1"));
       if ("image/jpg".equals(mimeType)) {
         mimeType = "image/jpeg";
       }
     } else {
       mimeTypeEndIndex = indexOfZeroByte(data, 0);
-      mimeType = Util.toLowerInvariant(new String(data, 0, mimeTypeEndIndex, "ISO-8859-1"));
+      mimeType = Ascii.toLowerCase(new String(data, 0, mimeTypeEndIndex, "ISO-8859-1"));
       if (mimeType.indexOf('/') == -1) {
         mimeType = "image/" + mimeType;
       }
diff --git a/library/common/src/main/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSource.java b/library/common/src/main/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSource.java
index 8c8b07607a..88193c2646 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSource.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/upstream/DefaultHttpDataSource.java
@@ -27,6 +27,7 @@ import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.upstream.DataSpec.HttpMethod;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import com.google.common.base.Predicate;
 import com.google.common.net.HttpHeaders;
 import java.io.IOException;
@@ -339,7 +340,7 @@ public class DefaultHttpDataSource extends BaseDataSource implements HttpDataSou
     } catch (IOException e) {
       @Nullable String message = e.getMessage();
       if (message != null
-          && Util.toLowerInvariant(message).matches("cleartext http traffic.*not permitted.*")) {
+          && Ascii.toLowerCase(message).matches("cleartext http traffic.*not permitted.*")) {
         throw new CleartextNotPermittedException(e, dataSpec);
       }
       throw new HttpDataSourceException(
diff --git a/library/common/src/main/java/com/google/android/exoplayer2/upstream/HttpDataSource.java b/library/common/src/main/java/com/google/android/exoplayer2/upstream/HttpDataSource.java
index e2ae38b013..6f20f53850 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/upstream/HttpDataSource.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/upstream/HttpDataSource.java
@@ -19,6 +19,7 @@ import android.text.TextUtils;
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import com.google.common.base.Predicate;
 import java.io.IOException;
 import java.lang.annotation.Documented;
@@ -182,7 +183,10 @@ public interface HttpDataSource extends DataSource {
   /** A {@link Predicate} that rejects content types often used for pay-walls. */
   Predicate<String> REJECT_PAYWALL_TYPES =
       contentType -> {
-        contentType = Util.toLowerInvariant(contentType);
+        if (contentType == null) {
+          return false;
+        }
+        contentType = Ascii.toLowerCase(contentType);
         return !TextUtils.isEmpty(contentType)
             && (!contentType.contains("text") || contentType.contains("text/vtt"))
             && !contentType.contains("html")
diff --git a/library/common/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java b/library/common/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java
index 13cf6b18c3..960dd8713d 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/util/MimeTypes.java
@@ -20,6 +20,7 @@ import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.audio.AacUtil;
+import com.google.common.base.Ascii;
 import java.util.ArrayList;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -340,7 +341,7 @@ public final class MimeTypes {
     if (codec == null) {
       return null;
     }
-    codec = Util.toLowerInvariant(codec.trim());
+    codec = Ascii.toLowerCase(codec.trim());
     if (codec.startsWith("avc1") || codec.startsWith("avc3")) {
       return MimeTypes.VIDEO_H264;
     } else if (codec.startsWith("hev1") || codec.startsWith("hvc1")) {
diff --git a/library/common/src/main/java/com/google/android/exoplayer2/util/Util.java b/library/common/src/main/java/com/google/android/exoplayer2/util/Util.java
index d04b4f8341..2d643673be 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/util/Util.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/util/Util.java
@@ -674,7 +674,7 @@ public final class Util {
       // Tag isn't valid, keep using the original.
       normalizedTag = language;
     }
-    normalizedTag = Util.toLowerInvariant(normalizedTag);
+    normalizedTag = Ascii.toLowerCase(normalizedTag);
     String mainLanguage = Util.splitAtFirst(normalizedTag, "-")[0];
     if (languageTagReplacementMap == null) {
       languageTagReplacementMap = createIsoLanguageReplacementMap();
@@ -760,16 +760,6 @@ public final class Util {
     return c == '\n' || c == '\r';
   }
 
-  /**
-   * Converts text to lower case using {@link Locale#US}.
-   *
-   * @param text The text to convert.
-   * @return The lower case text, or null if {@code text} is null.
-   */
-  public static @PolyNull String toLowerInvariant(@PolyNull String text) {
-    return text == null ? text : text.toLowerCase(Locale.US);
-  }
-
   /**
    * Converts text to upper case using {@link Locale#US}.
    *
@@ -1784,7 +1774,7 @@ public final class Util {
    * @return The derived {@link UUID}, or {@code null} if one could not be derived.
    */
   public static @Nullable UUID getDrmUuid(String drmScheme) {
-    switch (toLowerInvariant(drmScheme)) {
+    switch (Ascii.toLowerCase(drmScheme)) {
       case "widevine":
         return C.WIDEVINE_UUID;
       case "playready":
@@ -1834,7 +1824,7 @@ public final class Util {
    */
   @ContentType
   public static int inferContentType(String fileName) {
-    fileName = toLowerInvariant(fileName);
+    fileName = Ascii.toLowerCase(fileName);
     if (fileName.endsWith(".mpd")) {
       return C.TYPE_DASH;
     } else if (fileName.endsWith(".m3u8")) {
@@ -1907,11 +1897,11 @@ public final class Util {
    * @return The fixed URI.
    */
   public static Uri fixSmoothStreamingIsmManifestUri(Uri uri) {
-    @Nullable String path = toLowerInvariant(uri.getPath());
+    @Nullable String path = uri.getPath();
     if (path == null) {
       return uri;
     }
-    Matcher ismMatcher = ISM_URL_PATTERN.matcher(path);
+    Matcher ismMatcher = ISM_URL_PATTERN.matcher(Ascii.toLowerCase(path));
     if (ismMatcher.matches() && ismMatcher.group(1) == null) {
       // Add missing "Manifest" suffix.
       return Uri.withAppendedPath(uri, "Manifest");
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/AsynchronousMediaCodecBufferEnqueuer.java b/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/AsynchronousMediaCodecBufferEnqueuer.java
index 21f79a78a2..8a2bb9a9bc 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/AsynchronousMediaCodecBufferEnqueuer.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/AsynchronousMediaCodecBufferEnqueuer.java
@@ -30,6 +30,7 @@ import androidx.annotation.VisibleForTesting;
 import com.google.android.exoplayer2.decoder.CryptoInfo;
 import com.google.android.exoplayer2.util.ConditionVariable;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import java.util.ArrayDeque;
 import java.util.Arrays;
 import java.util.concurrent.atomic.AtomicReference;
@@ -303,7 +304,7 @@ class AsynchronousMediaCodecBufferEnqueuer {
    * buffers (see [Internal: b/149908061]).
    */
   private static boolean needsSynchronizationWorkaround() {
-    String manufacturer = Util.toLowerInvariant(Util.MANUFACTURER);
+    String manufacturer = Ascii.toLowerCase(Util.MANUFACTURER);
     return manufacturer.contains("samsung") || manufacturer.contains("motorola");
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecUtil.java b/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecUtil.java
index bcaf8a07b1..4df4ebed63 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecUtil.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/mediacodec/MediaCodecUtil.java
@@ -33,6 +33,7 @@ import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.Util;
 import com.google.android.exoplayer2.video.ColorInfo;
+import com.google.common.base.Ascii;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -624,7 +625,7 @@ public final class MediaCodecUtil {
     if (Util.SDK_INT >= 29) {
       return isSoftwareOnlyV29(codecInfo);
     }
-    String codecName = Util.toLowerInvariant(codecInfo.getName());
+    String codecName = Ascii.toLowerCase(codecInfo.getName());
     if (codecName.startsWith("arc.")) { // App Runtime for Chrome (ARC) codecs
       return false;
     }
@@ -650,7 +651,7 @@ public final class MediaCodecUtil {
     if (Util.SDK_INT >= 29) {
       return isVendorV29(codecInfo);
     }
-    String codecName = Util.toLowerInvariant(codecInfo.getName());
+    String codecName = Ascii.toLowerCase(codecInfo.getName());
     return !codecName.startsWith("omx.google.")
         && !codecName.startsWith("c2.android.")
         && !codecName.startsWith("c2.google.");
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/metadata/icy/IcyDecoder.java b/library/core/src/main/java/com/google/android/exoplayer2/metadata/icy/IcyDecoder.java
index 8f0254d83f..a97cb6a2ce 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/metadata/icy/IcyDecoder.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/metadata/icy/IcyDecoder.java
@@ -19,7 +19,7 @@ import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.metadata.MetadataInputBuffer;
 import com.google.android.exoplayer2.metadata.SimpleMetadataDecoder;
-import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import com.google.common.base.Charsets;
 import java.nio.ByteBuffer;
 import java.nio.charset.CharacterCodingException;
@@ -57,10 +57,10 @@ public final class IcyDecoder extends SimpleMetadataDecoder {
     int index = 0;
     Matcher matcher = METADATA_ELEMENT.matcher(icyString);
     while (matcher.find(index)) {
-      @Nullable String key = Util.toLowerInvariant(matcher.group(1));
+      @Nullable String key = matcher.group(1);
       @Nullable String value = matcher.group(2);
       if (key != null) {
-        switch (key) {
+        switch (Ascii.toLowerCase(key)) {
           case STREAM_KEY_NAME:
             name = value;
             break;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDecoder.java b/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDecoder.java
index 89366ca28c..eea43ad232 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDecoder.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDecoder.java
@@ -32,6 +32,7 @@ import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import java.util.ArrayList;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -154,7 +155,7 @@ public final class SsaDecoder extends SimpleSubtitleDecoder {
       if (infoNameAndValue.length != 2) {
         continue;
       }
-      switch (Util.toLowerInvariant(infoNameAndValue[0].trim())) {
+      switch (Ascii.toLowerCase(infoNameAndValue[0].trim())) {
         case "playresx":
           try {
             screenWidth = Float.parseFloat(infoNameAndValue[1].trim());
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDialogueFormat.java b/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDialogueFormat.java
index df3db09d73..82f3dd642c 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDialogueFormat.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaDialogueFormat.java
@@ -22,7 +22,7 @@ import android.text.TextUtils;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.util.Assertions;
-import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 
 /**
  * Represents a {@code Format:} line from the {@code [Events]} section
@@ -61,7 +61,7 @@ import com.google.android.exoplayer2.util.Util;
     Assertions.checkArgument(formatLine.startsWith(FORMAT_LINE_PREFIX));
     String[] keys = TextUtils.split(formatLine.substring(FORMAT_LINE_PREFIX.length()), ",");
     for (int i = 0; i < keys.length; i++) {
-      switch (Util.toLowerInvariant(keys[i].trim())) {
+      switch (Ascii.toLowerCase(keys[i].trim())) {
         case "start":
           startTimeIndex = i;
           break;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaStyle.java b/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaStyle.java
index 192838ad0d..7edddac118 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaStyle.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/text/ssa/SsaStyle.java
@@ -31,6 +31,7 @@ import com.google.android.exoplayer2.text.Cue;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import com.google.common.primitives.Ints;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
@@ -284,7 +285,7 @@ import java.util.regex.Pattern;
       String[] keys =
           TextUtils.split(styleFormatLine.substring(SsaDecoder.FORMAT_LINE_PREFIX.length()), ",");
       for (int i = 0; i < keys.length; i++) {
-        switch (Util.toLowerInvariant(keys[i].trim())) {
+        switch (Ascii.toLowerCase(keys[i].trim())) {
           case "name":
             nameIndex = i;
             break;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TextEmphasis.java b/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TextEmphasis.java
index a52d818c6e..ecfaeb27cd 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TextEmphasis.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TextEmphasis.java
@@ -23,6 +23,7 @@ import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.text.Cue;
 import com.google.android.exoplayer2.text.span.TextAnnotation;
 import com.google.android.exoplayer2.text.span.TextEmphasisSpan;
+import com.google.common.base.Ascii;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Sets;
@@ -131,7 +132,7 @@ import java.util.regex.Pattern;
       return null;
     }
 
-    String parsingValue = value.trim();
+    String parsingValue = Ascii.toLowerCase(value.trim());
     if (parsingValue.isEmpty()) {
       return null;
     }
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TtmlDecoder.java b/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TtmlDecoder.java
index 898fd01576..f06ca59546 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TtmlDecoder.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/text/ttml/TtmlDecoder.java
@@ -31,6 +31,7 @@ import com.google.android.exoplayer2.util.ColorParser;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.Util;
 import com.google.android.exoplayer2.util.XmlPullParserUtil;
+import com.google.common.base.Ascii;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.util.ArrayDeque;
@@ -432,7 +433,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
     String displayAlign =
         XmlPullParserUtil.getAttributeValue(xmlParser, TtmlNode.ATTR_TTS_DISPLAY_ALIGN);
     if (displayAlign != null) {
-      switch (Util.toLowerInvariant(displayAlign)) {
+      switch (Ascii.toLowerCase(displayAlign)) {
         case "center":
           lineAnchor = Cue.ANCHOR_TYPE_MIDDLE;
           line += height / 2;
@@ -454,7 +455,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
     String writingDirection =
         XmlPullParserUtil.getAttributeValue(xmlParser, TtmlNode.ATTR_TTS_WRITING_MODE);
     if (writingDirection != null) {
-      switch (Util.toLowerInvariant(writingDirection)) {
+      switch (Ascii.toLowerCase(writingDirection)) {
           // TODO: Support horizontal RTL modes.
         case TtmlNode.VERTICAL:
         case TtmlNode.VERTICAL_LR:
@@ -533,7 +534,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
               TtmlNode.ITALIC.equalsIgnoreCase(attributeValue));
           break;
         case TtmlNode.ATTR_TTS_TEXT_ALIGN:
-          switch (Util.toLowerInvariant(attributeValue)) {
+          switch (Ascii.toLowerCase(attributeValue)) {
             case TtmlNode.LEFT:
             case TtmlNode.START:
               style = createIfNull(style).setTextAlign(Layout.Alignment.ALIGN_NORMAL);
@@ -551,7 +552,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
           }
           break;
         case TtmlNode.ATTR_TTS_TEXT_COMBINE:
-          switch (Util.toLowerInvariant(attributeValue)) {
+          switch (Ascii.toLowerCase(attributeValue)) {
             case TtmlNode.COMBINE_NONE:
               style = createIfNull(style).setTextCombine(false);
               break;
@@ -564,7 +565,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
           }
           break;
         case TtmlNode.ATTR_TTS_RUBY:
-          switch (Util.toLowerInvariant(attributeValue)) {
+          switch (Ascii.toLowerCase(attributeValue)) {
             case TtmlNode.RUBY_CONTAINER:
               style = createIfNull(style).setRubyType(TtmlStyle.RUBY_TYPE_CONTAINER);
               break;
@@ -585,7 +586,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
           }
           break;
         case TtmlNode.ATTR_TTS_RUBY_POSITION:
-          switch (Util.toLowerInvariant(attributeValue)) {
+          switch (Ascii.toLowerCase(attributeValue)) {
             case TtmlNode.ANNOTATION_POSITION_BEFORE:
               style = createIfNull(style).setRubyPosition(TextAnnotation.POSITION_BEFORE);
               break;
@@ -598,7 +599,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
           }
           break;
         case TtmlNode.ATTR_TTS_TEXT_DECORATION:
-          switch (Util.toLowerInvariant(attributeValue)) {
+          switch (Ascii.toLowerCase(attributeValue)) {
             case TtmlNode.LINETHROUGH:
               style = createIfNull(style).setLinethrough(true);
               break;
@@ -614,9 +615,7 @@ public final class TtmlDecoder extends SimpleSubtitleDecoder {
           }
           break;
         case TtmlNode.ATTR_TTS_TEXT_EMPHASIS:
-          style =
-              createIfNull(style)
-                  .setTextEmphasis(TextEmphasis.parse(Util.toLowerInvariant(attributeValue)));
+          style = createIfNull(style).setTextEmphasis(TextEmphasis.parse(attributeValue));
           break;
         case TtmlNode.ATTR_TTS_SHEAR:
           style = createIfNull(style).setShearPercentage(parseShear(attributeValue));
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttCssStyle.java b/library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttCssStyle.java
index 45c66302c8..b8f9e9b343 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttCssStyle.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/text/webvtt/WebvttCssStyle.java
@@ -21,7 +21,7 @@ import androidx.annotation.ColorInt;
 import androidx.annotation.IntDef;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.text.span.TextAnnotation;
-import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -216,7 +216,7 @@ public final class WebvttCssStyle {
   }
 
   public WebvttCssStyle setFontFamily(@Nullable String fontFamily) {
-    this.fontFamily = Util.toLowerInvariant(fontFamily);
+    this.fontFamily = fontFamily == null ? null : Ascii.toLowerCase(fontFamily);
     return this;
   }
 
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/util/ColorParser.java b/library/core/src/main/java/com/google/android/exoplayer2/util/ColorParser.java
index 85ef43f669..6f35168d08 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/util/ColorParser.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/util/ColorParser.java
@@ -18,6 +18,7 @@ package com.google.android.exoplayer2.util;
 import android.graphics.Color;
 import android.text.TextUtils;
 import androidx.annotation.ColorInt;
+import com.google.common.base.Ascii;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.regex.Matcher;
@@ -106,7 +107,7 @@ public final class ColorParser {
       }
     } else {
       // we use our own color map
-      Integer color = COLOR_MAP.get(Util.toLowerInvariant(colorExpression));
+      Integer color = COLOR_MAP.get(Ascii.toLowerCase(colorExpression));
       if (color != null) {
         return color;
       }
diff --git a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/DashManifestParser.java b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/DashManifestParser.java
index 8c932f800d..3543aa312f 100644
--- a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/DashManifestParser.java
+++ b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/manifest/DashManifestParser.java
@@ -549,7 +549,7 @@ public class DashManifestParser extends DefaultHandler
 
     String schemeIdUri = xpp.getAttributeValue(null, "schemeIdUri");
     if (schemeIdUri != null) {
-      switch (Util.toLowerInvariant(schemeIdUri)) {
+      switch (Ascii.toLowerCase(schemeIdUri)) {
         case "urn:mpeg:dash:mp4protection:2011":
           schemeType = xpp.getAttributeValue(null, "value");
           String defaultKid = XmlPullParserUtil.getAttributeValueIgnorePrefix(xpp, "default_KID");
@@ -1798,11 +1798,11 @@ public class DashManifestParser extends DefaultHandler
    *     not be parsed.
    */
   protected static int parseDolbyChannelConfiguration(XmlPullParser xpp) {
-    String value = Util.toLowerInvariant(xpp.getAttributeValue(null, "value"));
+    @Nullable String value = xpp.getAttributeValue(null, "value");
     if (value == null) {
       return Format.NO_VALUE;
     }
-    switch (value) {
+    switch (Ascii.toLowerCase(value)) {
       case "4000":
         return 1;
       case "a000":
diff --git a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java
index 81cfcd2ef7..3527eb1fc3 100644
--- a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java
+++ b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaChunk.java
@@ -36,6 +36,7 @@ import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.TimestampAdjuster;
 import com.google.android.exoplayer2.util.UriUtil;
 import com.google.android.exoplayer2.util.Util;
+import com.google.common.base.Ascii;
 import com.google.common.collect.ImmutableList;
 import java.io.EOFException;
 import java.io.IOException;
@@ -540,7 +541,7 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
   private static byte[] getEncryptionIvArray(String ivString) {
     String trimmedIv;
-    if (Util.toLowerInvariant(ivString).startsWith("0x")) {
+    if (Ascii.toLowerCase(ivString).startsWith("0x")) {
       trimmedIv = ivString.substring(2);
     } else {
       trimmedIv = ivString;