OpenIPC · iflyhere · Aug 27, 2026
diff --git a/app/src/main/java/com/openipc/pixelpilot/VideoActivity.java b/app/src/main/java/com/openipc/pixelpilot/VideoActivity.java
@@ -165,6 +165,11 @@ public static int getChannel(Context context) {
                 Context.MODE_PRIVATE).getInt("wifi-channel", 161);
     }
 
+    public static boolean getLowLatencySetting(Context context) {
+        return context.getSharedPreferences("general",
+                Context.MODE_PRIVATE).getBoolean("low_latency_decoder", true);
+    }
+
     public static int getBandwidth(Context context) {
         return context.getSharedPreferences("general",
                 Context.MODE_PRIVATE).getInt("bandwidth", 20);
@@ -353,6 +358,7 @@ private void initializeWfbNg() {
     private void initializeVideoPlayers() {
         videoPlayer = new VideoPlayer(this);
         videoPlayer.setIVideoParamsChanged(this);
+        videoPlayer.setLowLatency(getLowLatencySetting(this));
 
         isVRMode = getVRSetting();
 
@@ -587,6 +593,9 @@ private void showSettingsMenu(View anchor) {
         // Bandwidth submenu
         setupBandwidthSubMenu(popup);
 
+        // Video submenu
+        setupVideoSubMenu(popup);
+
         // OSD submenu
         setupOSDSubMenu(popup);
 
@@ -671,6 +680,32 @@ private void setupBandwidthSubMenu(PopupMenu popup) {
         }
     }
 
+    /**
+     * Submenu for video decoder options.
+     * "Low latency" sets the MediaCodec low-latency and realtime-priority keys. It is on
+     * by default; decoders that misbehave with those keys can be put back on the stock
+     * pipeline here.
+     */
+    private void setupVideoSubMenu(PopupMenu popup) {
+        SubMenu videoMenu = popup.getMenu().addSubMenu("Video");
+
+        MenuItem lowLatencyItem = videoMenu.add("Low latency");
+        lowLatencyItem.setCheckable(true);
+        lowLatencyItem.setChecked(getLowLatencySetting(this));
+        lowLatencyItem.setOnMenuItemClickListener(item -> {
+            boolean enabled = !item.isChecked();
+            item.setChecked(enabled);
+            getSharedPreferences("general", MODE_PRIVATE).edit()
+                    .putBoolean("low_latency_decoder", enabled).apply();
+            videoPlayer.setLowLatency(enabled);
+            Toast.makeText(this, "Low latency " + (enabled ? "enabled" : "disabled")
+                    + ", applies on next video start.", Toast.LENGTH_SHORT).show();
+            item.setShowAsAction(MenuItem.SHOW_AS_ACTION_COLLAPSE_ACTION_VIEW);
+            item.setActionView(new View(this));
+            return false;
+        });
+    }
+
     /**
      * Submenu handling OSD toggles and locks.
      */

diff --git a/app/videonative/src/main/cpp/VideoDecoder.cpp b/app/videonative/src/main/cpp/VideoDecoder.cpp
@@ -135,15 +135,6 @@ void VideoDecoder::configureStartDecoder(int idx)
     AMediaFormat* format = AMediaFormat_new();
     AMediaFormat_setString(format, AMEDIAFORMAT_KEY_MIME, MIME.c_str());
 
-    // AMediaFormat_setInt32(format, "low-latency", 1);
-    // AMediaFormat_setInt32(format, "vendor.low-latency.enable", 1);
-    // AMediaFormat_setInt32(format, "vendor.qti-ext-dec-low-latency.enable", 1);
-    // AMediaFormat_setInt32(format, "vendor.hisi-ext-low-latency-video-dec.video-scene-for-low-latency-req", 1);
-    // AMediaFormat_setInt32(format, "vendor.rtc-ext-dec-low-latency.enable", 1);
-
-    // MediaCodec supports two priorities: 0 - realtime, 1 - best effort
-    // AMediaFormat_setInt32(format, "priority", 0);
-
     if (IS_H265)
     {
         h265_configureAMediaFormat(mKeyFrameFinder, format);
@@ -153,6 +144,11 @@ void VideoDecoder::configureStartDecoder(int idx)
         h264_configureAMediaFormat(mKeyFrameFinder, format);
     }
 
+    if (mLowLatency)
+    {
+        writeAndroidPerformanceParams(format);
+    }
+
     MLOGD << "Configuring decoder:" << AMediaFormat_toString(format);
 
     auto status = AMediaCodec_configure(decoder.codec[idx], format, decoder.window[idx], nullptr, 0);

diff --git a/app/videonative/src/main/cpp/VideoDecoder.h b/app/videonative/src/main/cpp/VideoDecoder.h
@@ -86,6 +86,10 @@ class VideoDecoder
 
     void registerOnDecodingInfoChangedCallback(DECODING_INFO_CHANGED_CALLBACK decodingInfoChangedCallback);
 
+    // Enable / disable the low-latency and realtime-priority AMediaFormat keys.
+    // Applied the next time the decoder is configured, not to a running decoder.
+    void setLowLatency(bool enabled) { mLowLatency = enabled; }
+
     // If the decoder has been configured, feed NALU. Else search for configuration data and
     // configure as soon as possible
     //  If the input pipe was closed (surface has been removed or is not set yet), only buffer key frames
@@ -109,6 +113,8 @@ class VideoDecoder
 
     std::unique_ptr<std::thread> mCheckOutputThread[2]  = {nullptr, nullptr};
     bool                         USE_SW_DECODER_INSTEAD = false;
+    // Some decoders misbehave with the low-latency keys, so it stays user switchable.
+    std::atomic<bool>            mLowLatency            = true;
     // Holds the AMediaCodec instance, as well as the state (configured or not configured)
     Decoder      decoder{};
     DecodingInfo decodingInfo;

diff --git a/app/videonative/src/main/cpp/VideoPlayer.cpp b/app/videonative/src/main/cpp/VideoPlayer.cpp
@@ -318,6 +318,16 @@ extern "C"
         }
     }
 
+    JNI_METHOD(void, nativeSetLowLatency)
+    (JNIEnv* env, jclass jclass1, jlong nativeInstance, jboolean enabled)
+    {
+        VideoPlayer* p = native(nativeInstance);
+        if (p)
+        {
+            p->setLowLatency(enabled);
+        }
+    }
+
     JNI_METHOD(void, nativeSetVideoSurface)
     (JNIEnv* env, jclass jclass1, jlong videoPlayerN, jobject surface, jint index)
     {

diff --git a/app/videonative/src/main/cpp/VideoPlayer.h b/app/videonative/src/main/cpp/VideoPlayer.h
@@ -54,6 +54,8 @@ class VideoPlayer
 
     void setForwarding(const std::string& ip, int port, bool enabled);
 
+    void setLowLatency(bool enabled) { videoDecoder.setLowLatency(enabled); }
+
   private:
     void onNewNALU(const NALU& nalu);
 

diff --git a/app/videonative/src/main/cpp/helper/AndroidMediaFormatHelper.h b/app/videonative/src/main/cpp/helper/AndroidMediaFormatHelper.h
@@ -5,26 +5,22 @@
 #include <media/NdkMediaFormat.h>
 #include "../NALU/KeyFrameFinder.hpp"
 
-// Some of these params are only supported on the latest Android versions
-// However,writing them has no negative affect on devices with older Android versions
-// Note that for example the low-latency key cannot fix any issues like the 'VUI' issue
-void writeAndroidPerformanceParams(AMediaFormat* format)
+// Decoder tuning that trades pipeline depth for latency. Unknown keys are ignored by
+// MediaCodec, so writing all of them is safe on every device / Android version.
+static void writeAndroidPerformanceParams(AMediaFormat* format)
 {
-    // I think: KEY_LOW_LATENCY is for decoder. But it doesn't really make a difference anyways
-    static const auto PARAMETER_KEY_LOW_LATENCY = "low-latency";
-    AMediaFormat_setInt32(format, PARAMETER_KEY_LOW_LATENCY, 1);
-    // Lower values mean higher priority
-    // Works on pixel 3 (look at output format description)
-    static const auto AMEDIAFORMAT_KEY_PRIORITY = "priority";
-    AMediaFormat_setInt32(format, AMEDIAFORMAT_KEY_PRIORITY, 0);
-    // set operating rate ? - doesn't make a difference
-    // static const auto AMEDIAFORMAT_KEY_OPERATING_RATE="operating-rate";
-    // AMediaFormat_setInt32(format,AMEDIAFORMAT_KEY_OPERATING_RATE,60);
-    //
-    // AMEDIAFORMAT_KEY_LOW_LATENCY;
-    // AMEDIAFORMAT_KEY_LATENCY;
-    // AMediaFormat_setInt32(format,AMEDIAFORMAT_KEY_LATENCY,0);
-    // AMediaFormat_setInt32(format,AMEDIAFORMAT_KEY_OPERATING_RATE,0);
+    // AMEDIAFORMAT_KEY_LOW_LATENCY (API 30+). Tells the decoder to output a frame as soon
+    // as it is decoded instead of keeping a reorder/output queue. For a live stream that
+    // never uses B-frames the queue only adds latency.
+    AMediaFormat_setInt32(format, "low-latency", 1);
+    // Vendor equivalents for SoCs whose codec does not pick up the AOSP key. Qualcomm is
+    // the relevant one for most phones and for the Snapdragon XR2 headsets.
+    AMediaFormat_setInt32(format, "vendor.low-latency.enable", 1);
+    AMediaFormat_setInt32(format, "vendor.qti-ext-dec-low-latency.enable", 1);
+    AMediaFormat_setInt32(format, "vendor.hisi-ext-low-latency-video-dec.video-scene-for-low-latency-req", 1);
+    AMediaFormat_setInt32(format, "vendor.rtc-ext-dec-low-latency.enable", 1);
+    // MediaCodec knows two priorities: 0 - realtime, 1 - best effort. Lower is higher.
+    AMediaFormat_setInt32(format, "priority", 0);
 }
 
 static void h264_configureAMediaFormat(KeyFrameFinder& kff, AMediaFormat* format)
@@ -42,7 +38,6 @@ static void h264_configureAMediaFormat(KeyFrameFinder& kff, AMediaFormat* format
     // AVCProfileBaseline==1
     // AMediaFormat_setInt32(decoder.format,AMEDIAFORMAT_KEY_PROFILE,1);
     // AMediaFormat_setInt32(decoder.format,AMEDIAFORMAT_KEY_PRIORITY,0);
-    // writeAndroidPerformanceParams(format);
 }
 
 static void h265_configureAMediaFormat(KeyFrameFinder& kff, AMediaFormat* format)
@@ -60,7 +55,6 @@ static void h265_configureAMediaFormat(KeyFrameFinder& kff, AMediaFormat* format
     AMediaFormat_setInt32(format, AMEDIAFORMAT_KEY_HEIGHT, videoWH[1]);
     AMediaFormat_setBuffer(format, "csd-0", buff.data(), buff.size());
     MLOGD << "Video WH:" << videoWH[0] << " H:" << videoWH[1];
-    // writeAndroidPerformanceParams(format);
 }
 
 #endif  // FPVUE_ANDROIDMEDIAFORMATHELPER_H
diff --git a/app/videonative/src/main/java/com/openipc/videonative/VideoPlayer.java b/app/videonative/src/main/java/com/openipc/videonative/VideoPlayer.java
@@ -52,6 +52,8 @@ public VideoPlayer(final AppCompatActivity parent) {
 
     public static native void nativeSetUdpForwarding(long nativeInstance, String ip, int port, boolean enabled);
 
+    public static native void nativeSetLowLatency(long nativeInstance, boolean enabled);
+
     public static native void nativeStartDvr(long nativeInstance, int fd, int fmp4_enabled);
 
     public static native void nativeStopDvr(long nativeInstance);
@@ -126,6 +128,14 @@ public boolean isRunning() {
         return timer != null;
     }
 
+    /**
+     * Enable/disable the low latency + realtime priority MediaCodec keys.
+     * Takes effect the next time the decoder is configured.
+     */
+    public void setLowLatency(boolean enabled) {
+        nativeSetLowLatency(nativeVideoPlayer, enabled);
+    }
+
     public void setUdpForwarding(String ip, int port, boolean enabled) {
         verifyApplicationThread();
         nativeSetUdpForwarding(nativeVideoPlayer, ip, port, enabled);