camera/camera-video/src/main/java/androidx/camera/video/internal/config/VideoEncoderConfigDefaultResolver.java

/*
 * Copyright 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.camera.video.internal.config;

import android.util.Range;
import android.util.Size;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;
import androidx.camera.core.Logger;
import androidx.camera.core.impl.Timebase;
import androidx.camera.video.VideoSpec;
import androidx.camera.video.internal.encoder.VideoEncoderConfig;
import androidx.core.util.Supplier;

/**
 * A {@link VideoEncoderConfig} supplier that resolves requested encoder settings from a
 * {@link VideoSpec} for the given surface {@link Size} using pre-defined default values.
 */
@RequiresApi(21) // TODO(b/200306659): Remove and replace with annotation on package-info.java
public class VideoEncoderConfigDefaultResolver implements Supplier<VideoEncoderConfig> {

    private static final String TAG = "VidEncCfgDefaultRslvr";

    // Base config based on generic 720p H264 quality will be scaled by actual source settings.
    // TODO: These should vary based on quality/codec and be derived from actual devices
    private static final int VIDEO_BITRATE_BASE = 14000000;
    private static final Size VIDEO_SIZE_BASE = new Size(1280, 720);
    private static final int VIDEO_FRAME_RATE_BASE = 30;
    private static final int VIDEO_FRAME_RATE_FIXED_DEFAULT = 30;
    private static final Range<Integer> VALID_FRAME_RATE_RANGE = new Range<>(1, 60);

    private final String mMimeType;

    private final Timebase mInputTimebase;
    private final VideoSpec mVideoSpec;
    private final Size mSurfaceSize;
    @Nullable
    private final Range<Integer> mExpectedFrameRateRange;

    /**
     * Constructor for a VideoEncoderConfigDefaultResolver.
     *
     * @param mimeType      The mime type for the video encoder
     * @param inputTimebase The time base of the input frame.
     * @param videoSpec     The {@link VideoSpec} which defines the settings that should be used
     *                      with the video encoder.
     * @param surfaceSize   The size of the surface required by the camera for the video encoder.
     */
    public VideoEncoderConfigDefaultResolver(@NonNull String mimeType,
            @NonNull Timebase inputTimebase, @NonNull VideoSpec videoSpec,
            @NonNull Size surfaceSize, @Nullable Range<Integer> expectedFrameRateRange) {
        mMimeType = mimeType;
        mInputTimebase = inputTimebase;
        mVideoSpec = videoSpec;
        mSurfaceSize = surfaceSize;
        mExpectedFrameRateRange = expectedFrameRateRange;
    }

    @Override
    @NonNull
    public VideoEncoderConfig get() {
        int resolvedFrameRate = resolveFrameRate();
        Logger.d(TAG, "Resolved VIDEO frame rate: " + resolvedFrameRate + "fps");

        Range<Integer> videoSpecBitrateRange = mVideoSpec.getBitrate();
        Logger.d(TAG, "Using fallback VIDEO bitrate");
        // We have no other information to go off of. Scale based on fallback defaults.
        int resolvedBitrate = VideoConfigUtil.scaleAndClampBitrate(
                VIDEO_BITRATE_BASE,
                resolvedFrameRate, VIDEO_FRAME_RATE_BASE,
                mSurfaceSize.getWidth(), VIDEO_SIZE_BASE.getWidth(),
                mSurfaceSize.getHeight(), VIDEO_SIZE_BASE.getHeight(),
                videoSpecBitrateRange);

        return VideoEncoderConfig.builder()
                .setMimeType(mMimeType)
                .setInputTimebase(mInputTimebase)
                .setResolution(mSurfaceSize)
                .setBitrate(resolvedBitrate)
                .setFrameRate(resolvedFrameRate)
                .build();
    }

    private int resolveFrameRate() {
        Range<Integer> videoSpecFrameRateRange = mVideoSpec.getFrameRate();
        // If the frame rate range isn't AUTO, we'll use the upper frame rate from the video spec
        // as our default in an attempt to maximize the quality of the video. However, we need to
        // ensure it is a valid frame rate, so clamp between 1 and 60fps.
        int defaultFrameRate;
        if (!VideoSpec.FRAME_RATE_RANGE_AUTO.equals(videoSpecFrameRateRange)) {
            defaultFrameRate = VALID_FRAME_RATE_RANGE.clamp(videoSpecFrameRateRange.getUpper());
        } else {
            // We have no information to base the frame rate on. Use a standard default.
            defaultFrameRate = VIDEO_FRAME_RATE_FIXED_DEFAULT;
        }

        Logger.d(TAG,
                String.format("Frame rate default: %dfps. [Requested range: %s, "
                                + "Expected operating range: %s]", defaultFrameRate,
                        videoSpecFrameRateRange, mExpectedFrameRateRange));

        return VideoConfigUtil.resolveFrameRate(
                /*preferredRange=*/ videoSpecFrameRateRange,
                /*exactFrameRateHint=*/ defaultFrameRate,
                /*strictOperatingFpsRange=*/mExpectedFrameRateRange);
    }
}