Only use 4 slices per frame on old Qualcomm devices that benefit from it

Using it everywhere decreases encoding efficiency for no gain in performance

app/src/main/java/com/limelight/binding/video/MediaCodecHelper.java

@@ -38,6 +38,7 @@ public class MediaCodecHelper {
     private static final List<String> whitelistedHevcDecoders;
     private static final List<String> refFrameInvalidationAvcPrefixes;
     private static final List<String> refFrameInvalidationHevcPrefixes;
+    private static final List<String> useFourSlicesPrefixes;
     private static final List<String> qualcommDecoderPrefixes;
     private static final List<String> kirinDecoderPrefixes;
     private static final List<String> exynosDecoderPrefixes;
@@ -201,6 +202,12 @@ public class MediaCodecHelper {
         // Qualcomm is currently the only decoders in this group.
     }
 
+    static {
+        useFourSlicesPrefixes = new LinkedList<>();
+
+        // This decoders are decided at runtime
+    }
+
     static {
         qualcommDecoderPrefixes = new LinkedList<>();
 
@@ -345,6 +352,9 @@ public class MediaCodecHelper {
             }
             else {
                 blacklistedDecoderPrefixes.add("OMX.qcom.video.decoder.hevc");
+
+                // These older decoders need 4 slices per frame for best performance
+                useFourSlicesPrefixes.add("omx.qcom");
             }
 
             // Older MediaTek SoCs have issues with HEVC rendering but the newer chips with
@@ -569,6 +579,17 @@ public class MediaCodecHelper {
         return isDecoderInList(baselineProfileHackPrefixes, decoderName);
     }
 
+    public static byte getDecoderOptimalSlicesPerFrame(String decoderName) {
+        if (isDecoderInList(useFourSlicesPrefixes, decoderName)) {
+            // 4 slices per frame reduces decoding latency on older Qualcomm devices
+            return 4;
+        }
+        else {
+            // 1 slice per frame produces the optimal encoding efficiency
+            return 1;
+        }
+    }
+
     public static boolean decoderSupportsRefFrameInvalidationAvc(String decoderName, int videoHeight) {
         // Reference frame invalidation is broken on low-end Snapdragon SoCs at 1080p.
         if (videoHeight > 720 && isLowEndSnapdragon) {