MediaCodecHelper.java

package com.limelight.binding.video;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import android.annotation.SuppressLint;
import android.app.ActivityManager;
import android.content.Context;
import android.content.pm.ConfigurationInfo;
import android.media.MediaCodec;
import android.media.MediaCodecInfo;
import android.media.MediaCodecList;
import android.media.MediaCodecInfo.CodecCapabilities;
import android.media.MediaCodecInfo.CodecProfileLevel;
import android.media.MediaFormat;
import android.os.Build;

import com.limelight.LimeLog;
import com.limelight.preferences.PreferenceConfiguration;

public class MediaCodecHelper {
    
    private static final List<String> preferredDecoders;

    private static final List<String> blacklistedDecoderPrefixes;
    private static final List<String> spsFixupBitstreamFixupDecoderPrefixes;
    private static final List<String> blacklistedAdaptivePlaybackPrefixes;
    private static final List<String> baselineProfileHackPrefixes;
    private static final List<String> directSubmitPrefixes;
    private static final List<String> constrainedHighProfilePrefixes;
    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;
    private static final List<String> amlogicDecoderPrefixes;
    private static final List<String> knownVendorLowLatencyOptions;

    public static final boolean SHOULD_BYPASS_SOFTWARE_BLOCK =
            Build.HARDWARE.equals("ranchu") || Build.HARDWARE.equals("cheets") || Build.BRAND.equals("Android-x86");

    private static boolean isLowEndSnapdragon = false;
    private static boolean isAdreno620 = false;
    private static boolean initialized = false;

    static {
        directSubmitPrefixes = new LinkedList<>();

        // These decoders have low enough input buffer latency that they
        // can be directly invoked from the receive thread
        directSubmitPrefixes.add("omx.qcom");
        directSubmitPrefixes.add("omx.sec");
        directSubmitPrefixes.add("omx.exynos");
        directSubmitPrefixes.add("omx.intel");
        directSubmitPrefixes.add("omx.brcm");
        directSubmitPrefixes.add("omx.TI");
        directSubmitPrefixes.add("omx.arc");
        directSubmitPrefixes.add("omx.nvidia");

        // All Codec2 decoders
        directSubmitPrefixes.add("c2.");
    }

    static {
        refFrameInvalidationAvcPrefixes = new LinkedList<>();

        refFrameInvalidationHevcPrefixes = new LinkedList<>();
        refFrameInvalidationHevcPrefixes.add("omx.exynos");
        refFrameInvalidationHevcPrefixes.add("c2.exynos");

        // Qualcomm and NVIDIA may be added at runtime
    }

    static {
        preferredDecoders = new LinkedList<>();
    }
    
    static {
        blacklistedDecoderPrefixes = new LinkedList<>();

        // Blacklist software decoders that don't support H264 high profile except on systems
        // that are expected to only have software decoders (like emulators).
        if (!SHOULD_BYPASS_SOFTWARE_BLOCK) {
            blacklistedDecoderPrefixes.add("omx.google");
            blacklistedDecoderPrefixes.add("AVCDecoder");

            // We want to avoid ffmpeg decoders since they're usually software decoders,
            // but we'll defer to the Android 10 isSoftwareOnly() API on newer devices
            // to determine if we should use these or not.
            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
                blacklistedDecoderPrefixes.add("OMX.ffmpeg");
            }
        }

        // Force these decoders disabled because:
        // 1) They are software decoders, so the performance is terrible
        // 2) They crash with our HEVC stream anyway (at least prior to CSD batching)
        blacklistedDecoderPrefixes.add("OMX.qcom.video.decoder.hevcswvdec");
        blacklistedDecoderPrefixes.add("OMX.SEC.hevc.sw.dec");
    }
    
    static {
        // If a decoder qualifies for reference frame invalidation,
        // these entries will be ignored for those decoders.
        spsFixupBitstreamFixupDecoderPrefixes = new LinkedList<>();
        spsFixupBitstreamFixupDecoderPrefixes.add("omx.nvidia");
        spsFixupBitstreamFixupDecoderPrefixes.add("omx.qcom");
        spsFixupBitstreamFixupDecoderPrefixes.add("omx.brcm");

        baselineProfileHackPrefixes = new LinkedList<>();
        baselineProfileHackPrefixes.add("omx.intel");

        blacklistedAdaptivePlaybackPrefixes = new LinkedList<>();
        // The Intel decoder on Lollipop on Nexus Player would increase latency badly
        // if adaptive playback was enabled so let's avoid it to be safe.
        blacklistedAdaptivePlaybackPrefixes.add("omx.intel");
        // The MediaTek decoder crashes at 1080p when adaptive playback is enabled
        // on some Android TV devices with HEVC only.
        blacklistedAdaptivePlaybackPrefixes.add("omx.mtk");

        constrainedHighProfilePrefixes = new LinkedList<>();
        constrainedHighProfilePrefixes.add("omx.intel");
    }

    static {
        whitelistedHevcDecoders = new LinkedList<>();

        // Allow software HEVC decoding in the official AOSP emulator
        if (Build.HARDWARE.equals("ranchu")) {
            whitelistedHevcDecoders.add("omx.google");
        }

        // Exynos seems to be the only HEVC decoder that works reliably
        whitelistedHevcDecoders.add("omx.exynos");

        // On Darcy (Shield 2017), HEVC runs fine with no fixups required. For some reason,
        // other X1 implementations require bitstream fixups. However, since numReferenceFrames
        // has been supported in GFE since late 2017, we'll go ahead and enable HEVC for all
        // device models.
        //
        // NVIDIA does partial HEVC acceleration on the Shield Tablet. I don't know
        // whether the performance is good enough to use for streaming, but they're
        // using the same omx.nvidia.h265.decode name as the Shield TV which has a
        // fully accelerated HEVC pipeline. AFAIK, the only K1 devices with this
        // partially accelerated HEVC decoder are the Shield Tablet and Xiaomi MiPad,
        // so I'll check for those here.
        //
        // In case there are some that I missed, I will also exclude pre-Oreo OSes since
        // only Shield ATV got an Oreo update and any newer Tegra devices will not ship
        // with an old OS like Nougat.
        if (!Build.DEVICE.equalsIgnoreCase("shieldtablet") &&
                !Build.DEVICE.equalsIgnoreCase("mocha") &&
                Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            whitelistedHevcDecoders.add("omx.nvidia");
        }

        // Plot twist: On newer Sony devices (BRAVIA_ATV2, BRAVIA_ATV3_4K, BRAVIA_UR1_4K) the H.264 decoder crashes
        // on several configurations (> 60 FPS and 1440p) that work with HEVC, so we'll whitelist those devices for HEVC.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O && Build.DEVICE.startsWith("BRAVIA_")) {
            whitelistedHevcDecoders.add("omx.mtk");
        }

        // Amlogic requires 1 reference frame for HEVC to avoid hanging. Since it's been years
        // since GFE added support for maxNumReferenceFrames, we'll just enable all Amlogic SoCs
        // running Android 9 or later.
        //
        // NB: We don't do this on Sabrina (GCWGTV) because H.264 is lower latency when we use
        // vendor.low-latency.enable. We will still use HEVC if decoderCanMeetPerformancePointWithHevcAndNotAvc()
        // determines it's the only way to meet the performance requirements.
        //
        // With the Android 12 update, Sabrina now uses HEVC (with RFI) based upon FEATURE_LowLatency
        // support, which provides equivalent latency to H.264 now.
        //
        // FIXME: Should we do this for all Amlogic S905X SoCs?
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P && !Build.DEVICE.equalsIgnoreCase("sabrina")) {
            whitelistedHevcDecoders.add("omx.amlogic");
        }

        // Realtek SoCs are used inside many Android TV devices and can only do 4K60 with HEVC.
        // We'll enable those HEVC decoders by default and see if anything breaks.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
            whitelistedHevcDecoders.add("omx.realtek");
        }

        // These theoretically have good HEVC decoding capabilities (potentially better than
        // their AVC decoders), but haven't been tested enough
        //whitelistedHevcDecoders.add("omx.rk");

        // Let's see if HEVC decoders are finally stable with C2
        whitelistedHevcDecoders.add("c2.");

        // Based on GPU attributes queried at runtime, the omx.qcom/c2.qti prefix will be added
        // during initialization to avoid SoCs with broken HEVC decoders.
    }

    static {
        useFourSlicesPrefixes = new LinkedList<>();

        // Software decoders will use 4 slices per frame to allow for slice multithreading
        useFourSlicesPrefixes.add("omx.google");
        useFourSlicesPrefixes.add("AVCDecoder");
        useFourSlicesPrefixes.add("omx.ffmpeg");
        useFourSlicesPrefixes.add("c2.android");

        // Old Qualcomm decoders are detected at runtime
    }

    static {
        knownVendorLowLatencyOptions = new LinkedList<>();

        knownVendorLowLatencyOptions.add("vendor.qti-ext-dec-low-latency.enable");
        knownVendorLowLatencyOptions.add("vendor.hisi-ext-low-latency-video-dec.video-scene-for-low-latency-req");
        knownVendorLowLatencyOptions.add("vendor.rtc-ext-dec-low-latency.enable");
        knownVendorLowLatencyOptions.add("vendor.low-latency.enable");
    }

    static {
        qualcommDecoderPrefixes = new LinkedList<>();

        qualcommDecoderPrefixes.add("omx.qcom");
        qualcommDecoderPrefixes.add("c2.qti");
    }

    static {
        kirinDecoderPrefixes = new LinkedList<>();

        kirinDecoderPrefixes.add("omx.hisi");
        kirinDecoderPrefixes.add("c2.hisi"); // Unconfirmed
    }

    static {
        exynosDecoderPrefixes = new LinkedList<>();

        exynosDecoderPrefixes.add("omx.exynos");
        exynosDecoderPrefixes.add("c2.exynos");
    }

    static {
        amlogicDecoderPrefixes = new LinkedList<>();

        amlogicDecoderPrefixes.add("omx.amlogic");
        amlogicDecoderPrefixes.add("c2.amlogic"); // Unconfirmed
    }

    private static boolean isPowerVR(String glRenderer) {
        return glRenderer.toLowerCase().contains("powervr");
    }

    private static String getAdrenoVersionString(String glRenderer) {
        glRenderer = glRenderer.toLowerCase().trim();

        if (!glRenderer.contains("adreno")) {
            return null;
        }

        Pattern modelNumberPattern = Pattern.compile("(.*)([0-9]{3})(.*)");

        Matcher matcher = modelNumberPattern.matcher(glRenderer);
        if (!matcher.matches()) {
            return null;
        }

        String modelNumber = matcher.group(2);
        LimeLog.info("Found Adreno GPU: "+modelNumber);
        return modelNumber;
    }

    private static boolean isLowEndSnapdragonRenderer(String glRenderer) {
        String modelNumber = getAdrenoVersionString(glRenderer);
        if (modelNumber == null) {
            // Not an Adreno GPU
            return false;
        }

        // The current logic is to identify low-end SoCs based on a zero in the x0x place.
        return modelNumber.charAt(1) == '0';
    }

    private static int getAdrenoRendererModelNumber(String glRenderer) {
        String modelNumber = getAdrenoVersionString(glRenderer);
        if (modelNumber == null) {
            // Not an Adreno GPU
            return -1;
        }

        return Integer.parseInt(modelNumber);
    }

    // This is a workaround for some broken devices that report
    // only GLES 3.0 even though the GPU is an Adreno 4xx series part.
    // An example of such a device is the Huawei Honor 5x with the
    // Snapdragon 616 SoC (Adreno 405).
    private static boolean isGLES31SnapdragonRenderer(String glRenderer) {
        // Snapdragon 4xx and higher support GLES 3.1
        return getAdrenoRendererModelNumber(glRenderer) >= 400;
    }

    public static void initialize(Context context, String glRenderer) {
        if (initialized) {
            return;
        }

        // Older Sony ATVs (SVP-DTV15) have broken MediaTek codecs (decoder hangs after rendering the first frame).
        // I know the Fire TV 2 and 3 works, so I'll whitelist Amazon devices which seem to actually be tested.
        // We still have to check Build.MANUFACTURER to catch Amazon Fire tablets.
        if (context.getPackageManager().hasSystemFeature("amazon.hardware.fire_tv") ||
                Build.MANUFACTURER.equalsIgnoreCase("Amazon")) {
            // HEVC and RFI have been confirmed working on Fire TV 2, Fire TV Stick 2, Fire TV 4K Max,
            // Fire HD 8 2020, and Fire HD 8 2022 models.
            //
            // This is probably a good enough sample to conclude that all MediaTek Fire OS devices
            // are likely to be okay.
            whitelistedHevcDecoders.add("omx.mtk");
            refFrameInvalidationHevcPrefixes.add("omx.mtk");
            refFrameInvalidationHevcPrefixes.add("c2.mtk");

            // This requires setting vdec-lowlatency on the Fire TV 3, otherwise the decoder
            // never produces any output frames. See comment above for details on why we only
            // do this for Fire TV devices.
            whitelistedHevcDecoders.add("omx.amlogic");

            // Fire TV 3 seems to produce random artifacts on HEVC streams after packet loss.
            // Enabling RFI turns these artifacts into full decoder output hangs, so let's not enable
            // that for Fire OS 6 Amlogic devices. We will leave HEVC enabled because that's the only
            // way these devices can hit 4K. Hopefully this is just a problem with the BSP used in
            // the Fire OS 6 Amlogic devices, so we will leave this enabled for Fire OS 7+.
            //
            // Apart from a few TV models, the main Amlogic-based Fire TV devices are the Fire TV
            // Cubes and Fire TV 3. This check will exclude the Fire TV 3 and Fire TV Cube 1, but
            // allow the newer Fire TV Cubes to use HEVC RFI.
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                refFrameInvalidationHevcPrefixes.add("omx.amlogic");
                refFrameInvalidationHevcPrefixes.add("c2.amlogic");
            }
        }

        ActivityManager activityManager =
                (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        ConfigurationInfo configInfo = activityManager.getDeviceConfigurationInfo();
        if (configInfo.reqGlEsVersion != ConfigurationInfo.GL_ES_VERSION_UNDEFINED) {
            LimeLog.info("OpenGL ES version: "+configInfo.reqGlEsVersion);

            isLowEndSnapdragon = isLowEndSnapdragonRenderer(glRenderer);
            isAdreno620 = getAdrenoRendererModelNumber(glRenderer) == 620;

            // Tegra K1 and later can do reference frame invalidation properly
            if (configInfo.reqGlEsVersion >= 0x30000) {
                LimeLog.info("Added omx.nvidia/c2.nvidia to reference frame invalidation support list");
                refFrameInvalidationAvcPrefixes.add("omx.nvidia");

                // Exclude HEVC RFI on Pixel C and Tegra devices prior to Android 11. Misbehaving RFI
                // on these devices can cause hundreds of milliseconds of latency, so it's not worth
                // using it unless we're absolutely sure that it will not cause increased latency.
                if (!Build.DEVICE.equalsIgnoreCase("dragon") && Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
                    refFrameInvalidationHevcPrefixes.add("omx.nvidia");
                }

                refFrameInvalidationAvcPrefixes.add("c2.nvidia"); // Unconfirmed
                refFrameInvalidationHevcPrefixes.add("c2.nvidia"); // Unconfirmed

                LimeLog.info("Added omx.qcom/c2.qti to reference frame invalidation support list");
                refFrameInvalidationAvcPrefixes.add("omx.qcom");
                refFrameInvalidationHevcPrefixes.add("omx.qcom");
                refFrameInvalidationAvcPrefixes.add("c2.qti");
                refFrameInvalidationHevcPrefixes.add("c2.qti");
            }

            // Qualcomm's early HEVC decoders break hard on our HEVC stream. The best check to
            // tell the good from the bad decoders are the generation of Adreno GPU included:
            // 3xx - bad
            // 4xx - good
            //
            // The "good" GPUs support GLES 3.1, but we can't just check that directly
            // (see comment on isGLES31SnapdragonRenderer).
            //
            if (isGLES31SnapdragonRenderer(glRenderer)) {
                LimeLog.info("Added omx.qcom/c2.qti to HEVC decoders based on GLES 3.1+ support");
                whitelistedHevcDecoders.add("omx.qcom");
                whitelistedHevcDecoders.add("c2.qti");
            }
            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
            // PowerVR GPUs have good HEVC support.
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N && isPowerVR(glRenderer)) {
                LimeLog.info("Added omx.mtk to HEVC decoders based on PowerVR GPU");
                whitelistedHevcDecoders.add("omx.mtk");

                // This SoC (MT8176 in GPD XD+) supports AVC RFI too, but the maxNumReferenceFrames setting
                // required to make it work adds a huge amount of latency. However, RFI on HEVC causes
                // decoder hangs on the newer GE8100, GE8300, and GE8320 GPUs, so we limit it to the
                // Series6XT GPUs where we know it works.
                if (glRenderer.contains("GX6")) {
                    LimeLog.info("Added omx.mtk/c2.mtk to RFI list for HEVC");
                    refFrameInvalidationHevcPrefixes.add("omx.mtk");
                    refFrameInvalidationHevcPrefixes.add("c2.mtk");
                }
            }
        }

        initialized = true;
    }

    private static boolean isDecoderInList(List<String> decoderList, String decoderName) {
        if (!initialized) {
            throw new IllegalStateException("MediaCodecHelper must be initialized before use");
        }

        for (String badPrefix : decoderList) {
            if (decoderName.length() >= badPrefix.length()) {
                String prefix = decoderName.substring(0, badPrefix.length());
                if (prefix.equalsIgnoreCase(badPrefix)) {
                    return true;
                }
            }
        }
        
        return false;
    }

    private static boolean decoderSupportsAndroidRLowLatency(MediaCodecInfo decoderInfo, String mimeType) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
            try {
                if (decoderInfo.getCapabilitiesForType(mimeType).isFeatureSupported(CodecCapabilities.FEATURE_LowLatency)) {
                    LimeLog.info("Low latency decoding mode supported (FEATURE_LowLatency)");
                    return true;
                }
            } catch (Exception e) {
                // Tolerate buggy codecs
                e.printStackTrace();
            }
        }

        return false;
    }

    private static boolean decoderSupportsKnownVendorLowLatencyOption(String decoderName) {
        // It's only possible to probe vendor parameters on Android 12 and above.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            MediaCodec testCodec = null;
            try {
                // Unfortunately we have to create an actual codec instance to get supported options.
                testCodec = MediaCodec.createByCodecName(decoderName);

                // See if any of the vendor parameters match ones we know about
                for (String supportedOption : testCodec.getSupportedVendorParameters()) {
                    for (String knownLowLatencyOption : knownVendorLowLatencyOptions) {
                        if (supportedOption.equalsIgnoreCase(knownLowLatencyOption)) {
                            LimeLog.info(decoderName + " supports known low latency option: " + supportedOption);
                            return true;
                        }
                    }
                }
            } catch (Exception e) {
                // Tolerate buggy codecs
                e.printStackTrace();
            } finally {
                if (testCodec != null) {
                    testCodec.release();
                }
            }
        }
        return false;
    }

    private static boolean decoderSupportsMaxOperatingRate(String decoderName) {
        // Operate at maximum rate to lower latency as much as possible on
        // some Qualcomm platforms. We could also set KEY_PRIORITY to 0 (realtime)
        // but that will actually result in the decoder crashing if it can't satisfy
        // our (ludicrous) operating rate requirement. This seems to cause reliable
        // crashes on the Xiaomi Mi 10 lite 5G and Redmi K30i 5G on Android 10, so
        // we'll disable it on Snapdragon 765G and all non-Qualcomm devices to be safe.
        //
        // NB: Even on Android 10, this optimization still provides significant
        // performance gains on Pixel 2.
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.M &&
                isDecoderInList(qualcommDecoderPrefixes, decoderName) &&
                !isAdreno620;
    }

    public static boolean setDecoderLowLatencyOptions(MediaFormat videoFormat, MediaCodecInfo decoderInfo, int tryNumber) {
        // Options here should be tried in the order of most to least risky. The decoder will use
        // the first MediaFormat that doesn't fail in configure().

        boolean setNewOption = false;

        if (tryNumber < 1) {
            // Official Android 11+ low latency option (KEY_LOW_LATENCY).
            videoFormat.setInteger("low-latency", 1);
            setNewOption = true;

            // If this decoder officially supports FEATURE_LowLatency, we will just use that alone
            // for try 0. Otherwise, we'll include it as best effort with other options.
            if (decoderSupportsAndroidRLowLatency(decoderInfo, videoFormat.getString(MediaFormat.KEY_MIME))) {
                return true;
            }
        }

        if (tryNumber < 2 &&
                (!Build.MANUFACTURER.equalsIgnoreCase("xiaomi") || Build.VERSION.SDK_INT > Build.VERSION_CODES.M)) {
            // MediaTek decoders don't use vendor-defined keys for low latency mode. Instead, they have a modified
            // version of AOSP's ACodec.cpp which supports the "vdec-lowlatency" option. This option is passed down
            // to the decoder as OMX.MTK.index.param.video.LowLatencyDecode.
            //
            // This option is also plumbed for Amazon Amlogic-based devices like the Fire TV 3. Not only does it
            // reduce latency on Amlogic, it fixes the HEVC bug that causes the decoder to not output any frames.
            // Unfortunately, it does the exact opposite for the Xiaomi MITV4-ANSM0, breaking it in the way that
            // Fire TV was broken prior to vdec-lowlatency :(
            //
            // On Fire TV 3, vdec-lowlatency is translated to OMX.amazon.fireos.index.video.lowLatencyDecode.
            //
            // https://github.com/yuan1617/Framwork/blob/master/frameworks/av/media/libstagefright/ACodec.cpp
            // https://github.com/iykex/vendor_mediatek_proprietary_hardware/blob/master/libomx/video/MtkOmxVdecEx/MtkOmxVdecEx.h
            videoFormat.setInteger("vdec-lowlatency", 1);
            setNewOption = true;
        }

        if (tryNumber < 3) {
            if (MediaCodecHelper.decoderSupportsMaxOperatingRate(decoderInfo.getName())) {
                videoFormat.setInteger(MediaFormat.KEY_OPERATING_RATE, Short.MAX_VALUE);
                setNewOption = true;
            }
            else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                videoFormat.setInteger(MediaFormat.KEY_PRIORITY, 0);
                setNewOption = true;
            }
        }

        // MediaCodec supports vendor-defined format keys using the "vendor.<extension name>.<parameter name>" syntax.
        // These allow access to functionality that is not exposed through documented MediaFormat.KEY_* values.
        // https://cs.android.com/android/platform/superproject/+/master:hardware/qcom/sdm845/media/mm-video-v4l2/vidc/common/inc/vidc_vendor_extensions.h;l=67
        //
        // MediaCodec vendor extension support was introduced in Android 8.0:
        // https://cs.android.com/android/_/android/platform/frameworks/av/+/01c10f8cdcd58d1e7025f426a72e6e75ba5d7fc2
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            // Try vendor-specific low latency options
            //
            // NOTE: Update knownVendorLowLatencyOptions if you modify this code!
            if (isDecoderInList(qualcommDecoderPrefixes, decoderInfo.getName())) {
                // Examples of Qualcomm's vendor extensions for Snapdragon 845:
                // https://cs.android.com/android/platform/superproject/+/master:hardware/qcom/sdm845/media/mm-video-v4l2/vidc/vdec/src/omx_vdec_extensions.hpp
                // https://cs.android.com/android/_/android/platform/hardware/qcom/sm8150/media/+/0621ceb1c1b19564999db8293574a0e12952ff6c
                //
                // We will first try both, then try vendor.qti-ext-dec-low-latency.enable alone if that fails
                if (tryNumber < 4) {
                    videoFormat.setInteger("vendor.qti-ext-dec-picture-order.enable", 1);
                    setNewOption = true;
                }
                if (tryNumber < 5) {
                    videoFormat.setInteger("vendor.qti-ext-dec-low-latency.enable", 1);
                    setNewOption = true;
                }
            }
            else if (isDecoderInList(kirinDecoderPrefixes, decoderInfo.getName())) {
                if (tryNumber < 4) {
                    // Kirin low latency options
                    // https://developer.huawei.com/consumer/cn/forum/topic/0202325564295980115
                    videoFormat.setInteger("vendor.hisi-ext-low-latency-video-dec.video-scene-for-low-latency-req", 1);
                    videoFormat.setInteger("vendor.hisi-ext-low-latency-video-dec.video-scene-for-low-latency-rdy", -1);
                    setNewOption = true;
                }
            }
            else if (isDecoderInList(exynosDecoderPrefixes, decoderInfo.getName())) {
                if (tryNumber < 4) {
                    // Exynos low latency option for H.264 decoder
                    videoFormat.setInteger("vendor.rtc-ext-dec-low-latency.enable", 1);
                    setNewOption = true;
                }
            }
            else if (isDecoderInList(amlogicDecoderPrefixes, decoderInfo.getName())) {
                if (tryNumber < 4) {
                    // Amlogic low latency vendor extension
                    // https://github.com/codewalkerster/android_vendor_amlogic_common_prebuilt_libstagefrighthw/commit/41fefc4e035c476d58491324a5fe7666bfc2989e
                    videoFormat.setInteger("vendor.low-latency.enable", 1);
                    setNewOption = true;
                }
            }
        }

        return setNewOption;
    }

    public static boolean decoderSupportsFusedIdrFrame(MediaCodecInfo decoderInfo, String mimeType) {
        // If adaptive playback is supported, we can submit new CSD together with a keyframe
        try {
            if (decoderInfo.getCapabilitiesForType(mimeType).
                    isFeatureSupported(CodecCapabilities.FEATURE_AdaptivePlayback)) {
                LimeLog.info("Decoder supports fused IDR frames (FEATURE_AdaptivePlayback)");
                return true;
            }
        } catch (Exception e) {
            // Tolerate buggy codecs
            e.printStackTrace();
        }

        return false;
    }

    public static boolean decoderSupportsAdaptivePlayback(MediaCodecInfo decoderInfo, String mimeType) {
        if (isDecoderInList(blacklistedAdaptivePlaybackPrefixes, decoderInfo.getName())) {
            LimeLog.info("Decoder blacklisted for adaptive playback");
            return false;
        }

        try {
            if (decoderInfo.getCapabilitiesForType(mimeType).
                    isFeatureSupported(CodecCapabilities.FEATURE_AdaptivePlayback))
            {
                // This will make getCapabilities() return that adaptive playback is supported
                LimeLog.info("Adaptive playback supported (FEATURE_AdaptivePlayback)");
                return true;
            }
        } catch (Exception e) {
            // Tolerate buggy codecs
            e.printStackTrace();
        }

        return false;
    }

    public static boolean decoderNeedsConstrainedHighProfile(String decoderName) {
        return isDecoderInList(constrainedHighProfilePrefixes, decoderName);
    }

    public static boolean decoderCanDirectSubmit(String decoderName) {
        return isDecoderInList(directSubmitPrefixes, decoderName) && !isExynos4Device();
    }
    
    public static boolean decoderNeedsSpsBitstreamRestrictions(String decoderName) {
        return isDecoderInList(spsFixupBitstreamFixupDecoderPrefixes, decoderName);
    }

    public static boolean decoderNeedsBaselineSpsHack(String decoderName) {
        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) {
            return false;
        }

        // This device seems to crash constantly at 720p, so try disabling
        // RFI to see if we can get that under control.
        if (Build.DEVICE.equals("b3") || Build.DEVICE.equals("b5")) {
            return false;
        }

        return isDecoderInList(refFrameInvalidationAvcPrefixes, decoderName);
    }

    public static boolean decoderSupportsRefFrameInvalidationHevc(MediaCodecInfo decoderInfo) {
        // HEVC decoders seem to universally support RFI, but it can have huge latency penalties
        // for some decoders due to the number of references frames being > 1. Old Amlogic
        // decoders are known to have this problem.
        //
        // If the decoder supports FEATURE_LowLatency or any vendor low latency option,
        // we will use that as an indication that it can handle HEVC RFI without excessively
        // buffering frames.
        if (decoderSupportsAndroidRLowLatency(decoderInfo, "video/hevc") ||
                decoderSupportsKnownVendorLowLatencyOption(decoderInfo.getName())) {
            LimeLog.info("Enabling HEVC RFI based on low latency option support");
            return true;
        }

        return isDecoderInList(refFrameInvalidationHevcPrefixes, decoderInfo.getName());
    }

    public static boolean decoderSupportsRefFrameInvalidationAv1(MediaCodecInfo decoderInfo) {
        // We'll use the same heuristics as HEVC for now
        if (decoderSupportsAndroidRLowLatency(decoderInfo, "video/av01") ||
                decoderSupportsKnownVendorLowLatencyOption(decoderInfo.getName())) {
            LimeLog.info("Enabling AV1 RFI based on low latency option support");
            return true;
        }

        return false;
    }

    public static boolean decoderIsWhitelistedForHevc(MediaCodecInfo decoderInfo) {
        //
        // Software decoders are terrible and we never want to use them.
        // We want to catch decoders like:
        // OMX.qcom.video.decoder.hevcswvdec
        // OMX.SEC.hevc.sw.dec
        //
        if (decoderInfo.getName().contains("sw")) {
            LimeLog.info("Disallowing HEVC on software decoder: " + decoderInfo.getName());
            return false;
        }
        else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q && (!decoderInfo.isHardwareAccelerated() || decoderInfo.isSoftwareOnly())) {
            LimeLog.info("Disallowing HEVC on software decoder: " + decoderInfo.getName());
            return false;
        }

        // If this device is media performance class 12 or higher, we will assume any hardware
        // HEVC decoder present is fast and modern enough for streaming.
        //
        // [5.3/H-1-1] MUST NOT drop more than 2 frames in 10 seconds (i.e less than 0.333 percent frame drop) for a 1080p 60 fps video session under load.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
            LimeLog.info("Media performance class: " + Build.VERSION.MEDIA_PERFORMANCE_CLASS);
            if (Build.VERSION.MEDIA_PERFORMANCE_CLASS >= Build.VERSION_CODES.S) {
                LimeLog.info("Allowing HEVC based on media performance class");
                return true;
            }
        }

        // If the decoder supports FEATURE_LowLatency, we will assume it is fast and modern enough
        // to be preferable for streaming over H.264 decoders.
        if (decoderSupportsAndroidRLowLatency(decoderInfo, "video/hevc")) {
            LimeLog.info("Allowing HEVC based on FEATURE_LowLatency support");
            return true;
        }

        // Otherwise, we use our list of known working HEVC decoders
        return isDecoderInList(whitelistedHevcDecoders, decoderInfo.getName());
    }

    public static boolean isDecoderWhitelistedForAv1(MediaCodecInfo decoderInfo) {
        // Google didn't have official support for AV1 (or more importantly, a CTS test) until
        // Android 10, so don't use any decoder before then.
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
            return false;
        }

        //
        // Software decoders are terrible and we never want to use them.
        // We want to catch decoders like:
        // OMX.qcom.video.decoder.hevcswvdec
        // OMX.SEC.hevc.sw.dec
        //
        if (decoderInfo.getName().contains("sw")) {
            LimeLog.info("Disallowing AV1 on software decoder: " + decoderInfo.getName());
            return false;
        }
        else if (!decoderInfo.isHardwareAccelerated() || decoderInfo.isSoftwareOnly()) {
            LimeLog.info("Disallowing AV1 on software decoder: " + decoderInfo.getName());
            return false;
        }

        // TODO: Test some AV1 decoders
        return false;
    }

    @SuppressWarnings("deprecation")
    @SuppressLint("NewApi")
    private static LinkedList<MediaCodecInfo> getMediaCodecList() {
        LinkedList<MediaCodecInfo> infoList = new LinkedList<>();

        MediaCodecList mcl = new MediaCodecList(MediaCodecList.REGULAR_CODECS);
        Collections.addAll(infoList, mcl.getCodecInfos());

        return infoList;
    }
    
    @SuppressWarnings("RedundantThrows")
    public static String dumpDecoders() throws Exception {
        String str = "";
        for (MediaCodecInfo codecInfo : getMediaCodecList()) {
            // Skip encoders
            if (codecInfo.isEncoder()) {
                continue;
            }
            
            str += "Decoder: "+codecInfo.getName()+"\n";
            for (String type : codecInfo.getSupportedTypes()) {
                str += "\t"+type+"\n";
                CodecCapabilities caps = codecInfo.getCapabilitiesForType(type);
                
                for (CodecProfileLevel profile : caps.profileLevels) {
                    str += "\t\t"+profile.profile+" "+profile.level+"\n";
                }
            }
        }
        return str;
    }
    
    private static MediaCodecInfo findPreferredDecoder() {
        // This is a different algorithm than the other findXXXDecoder functions,
        // because we want to evaluate the decoders in our list's order
        // rather than MediaCodecList's order

        if (!initialized) {
            throw new IllegalStateException("MediaCodecHelper must be initialized before use");
        }
        
        for (String preferredDecoder : preferredDecoders) {
            for (MediaCodecInfo codecInfo : getMediaCodecList()) {
                // Skip encoders
                if (codecInfo.isEncoder()) {
                    continue;
                }
                
                // Check for preferred decoders
                if (preferredDecoder.equalsIgnoreCase(codecInfo.getName())) {
                    LimeLog.info("Preferred decoder choice is "+codecInfo.getName());
                    return codecInfo;
                }
            }
        }
        
        return null;
    }

    private static boolean isCodecBlacklisted(MediaCodecInfo codecInfo) {
        // Use the new isSoftwareOnly() function on Android Q
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
            if (!SHOULD_BYPASS_SOFTWARE_BLOCK && codecInfo.isSoftwareOnly()) {
                LimeLog.info("Skipping software-only decoder: "+codecInfo.getName());
                return true;
            }
        }

        // Check for explicitly blacklisted decoders
        if (isDecoderInList(blacklistedDecoderPrefixes, codecInfo.getName())) {
            LimeLog.info("Skipping blacklisted decoder: "+codecInfo.getName());
            return true;
        }

        return false;
    }
    
    public static MediaCodecInfo findFirstDecoder(String mimeType) {
        for (MediaCodecInfo codecInfo : getMediaCodecList()) {
            // Skip encoders
            if (codecInfo.isEncoder()) {
                continue;
            }

            // Skip compatibility aliases on Q+
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                if (codecInfo.isAlias()) {
                    continue;
                }
            }
            
            // Find a decoder that supports the specified video format
            for (String mime : codecInfo.getSupportedTypes()) {
                if (mime.equalsIgnoreCase(mimeType)) {
                    // Skip blacklisted codecs
                    if (isCodecBlacklisted(codecInfo)) {
                        continue;
                    }

                    LimeLog.info("First decoder choice is "+codecInfo.getName());
                    return codecInfo;
                }
            }
        }
        
        return null;
    }
    
    public static MediaCodecInfo findProbableSafeDecoder(String mimeType, int requiredProfile) {
        // First look for a preferred decoder by name
        MediaCodecInfo info = findPreferredDecoder();
        if (info != null) {
            return info;
        }
        
        // Now look for decoders we know are safe
        try {
            // If this function completes, it will determine if the decoder is safe
            return findKnownSafeDecoder(mimeType, requiredProfile);
        } catch (Exception e) {
            // Some buggy devices seem to throw exceptions
            // from getCapabilitiesForType() so we'll just assume
            // they're okay and go with the first one we find
            return findFirstDecoder(mimeType);
        }
    }

    // We declare this method as explicitly throwing Exception
    // since some bad decoders can throw IllegalArgumentExceptions unexpectedly
    // and we want to be sure all callers are handling this possibility
    @SuppressWarnings("RedundantThrows")
    private static MediaCodecInfo findKnownSafeDecoder(String mimeType, int requiredProfile) throws Exception {
        // Some devices (Exynos devces, at least) have two sets of decoders.
        // The first set of decoders are C2 which do not support FEATURE_LowLatency,
        // but the second set of OMX decoders do support FEATURE_LowLatency. We want
        // to pick the OMX decoders despite the fact that C2 is listed first.
        // On some Qualcomm devices (like Pixel 4), there are separate low latency decoders
        // (like c2.qti.hevc.decoder.low_latency) that advertise FEATURE_LowLatency while
        // the standard ones (like c2.qti.hevc.decoder) do not. Like Exynos, the decoders
        // with FEATURE_LowLatency support are listed after the standard ones.
        for (int i = 0; i < 2; i++) {
            for (MediaCodecInfo codecInfo : getMediaCodecList()) {
                // Skip encoders
                if (codecInfo.isEncoder()) {
                    continue;
                }

                // Skip compatibility aliases on Q+
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
                    if (codecInfo.isAlias()) {
                        continue;
                    }
                }

                // Find a decoder that supports the requested video format
                for (String mime : codecInfo.getSupportedTypes()) {
                    if (mime.equalsIgnoreCase(mimeType)) {
                        LimeLog.info("Examining decoder capabilities of " + codecInfo.getName() + " (round " + (i + 1) + ")");

                        // Skip blacklisted codecs
                        if (isCodecBlacklisted(codecInfo)) {
                            continue;
                        }

                        CodecCapabilities caps = codecInfo.getCapabilitiesForType(mime);

                        if (i == 0 && !decoderSupportsAndroidRLowLatency(codecInfo, mime)) {
                            LimeLog.info("Skipping decoder that lacks FEATURE_LowLatency for round 1");
                            continue;
                        }

                        if (requiredProfile != -1) {
                            for (CodecProfileLevel profile : caps.profileLevels) {
                                if (profile.profile == requiredProfile) {
                                    LimeLog.info("Decoder " + codecInfo.getName() + " supports required profile");
                                    return codecInfo;
                                }
                            }

                            LimeLog.info("Decoder " + codecInfo.getName() + " does NOT support required profile");
                        } else {
                            return codecInfo;
                        }
                    }
                }
            }
        }
        
        return null;
    }
    
    public static String readCpuinfo() throws Exception {
        StringBuilder cpuInfo = new StringBuilder();
        try (final BufferedReader br = new BufferedReader(new FileReader(new File("/proc/cpuinfo")))) {
            for (;;) {
                int ch = br.read();
                if (ch == -1)
                    break;
                cpuInfo.append((char)ch);
            }

            return cpuInfo.toString();
        }
    }
    
    private static boolean stringContainsIgnoreCase(String string, String substring) {
        return string.toLowerCase(Locale.ENGLISH).contains(substring.toLowerCase(Locale.ENGLISH));
    }
    
    public static boolean isExynos4Device() {
        try {
            // Try reading CPU info too look for 
            String cpuInfo = readCpuinfo();
            
            // SMDK4xxx is Exynos 4 
            if (stringContainsIgnoreCase(cpuInfo, "SMDK4")) {
                LimeLog.info("Found SMDK4 in /proc/cpuinfo");
                return true;
            }
            
            // If we see "Exynos 4" also we'll count it
            if (stringContainsIgnoreCase(cpuInfo, "Exynos 4")) {
                LimeLog.info("Found Exynos 4 in /proc/cpuinfo");
                return true;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        try {
            File systemDir = new File("/sys/devices/system");
            File[] files = systemDir.listFiles();
            if (files != null) {
                for (File f : files) {
                    if (stringContainsIgnoreCase(f.getName(), "exynos4")) {
                        LimeLog.info("Found exynos4 in /sys/devices/system");
                        return true;
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        return false;
    }
}