FrameDroppingShaderProgram.java
/*
* Copyright 2023 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.media3.effect;
import static androidx.media3.common.util.Assertions.checkNotNull;
import static java.lang.Math.abs;
import android.content.Context;
import androidx.annotation.Nullable;
import androidx.media3.common.C;
import androidx.media3.common.GlTextureInfo;
import androidx.media3.common.VideoFrameProcessingException;
// TODO(b/227625363): Add tests for this file.
/**
* Drops frames by only queuing input frames that are chosen by the frame dropping strategy.
*
* <p>The strategy used is to queue the current frame, x, with timestamp T_x if and only if one of
* the following is true:
*
* <ul>
* <li>x is the first frame,
* <li>(T_x - T_lastQueued) is closer to the target frame interval than (T_(x+1) - T_lastQueued)
* </ul>
*
* <p>Where T_lastQueued is the timestamp of the last queued frame and T_(x+1) is the timestamp of
* the next frame. The target frame interval is determined from {@code targetFps}.
*/
/* package */ final class FrameDroppingShaderProgram extends FrameCacheGlShaderProgram {
private final long targetFrameDeltaUs;
@Nullable private GlTextureInfo previousTexture;
private long previousPresentationTimeUs;
private long lastQueuedPresentationTimeUs;
private boolean isPreviousFrameFirstFrame;
/**
* Creates a new instance.
*
* @param context The {@link Context}.
* @param useHdr Whether input textures come from an HDR source. If {@code true}, colors will be
* in linear RGB BT.2020. If {@code false}, colors will be in linear RGB BT.709.
* @param targetFps The number of frames per second the output video should roughly have.
*/
public FrameDroppingShaderProgram(Context context, boolean useHdr, float targetFps)
throws VideoFrameProcessingException {
super(context, /* capacity= */ 1, useHdr);
this.targetFrameDeltaUs = (long) (C.MICROS_PER_SECOND / targetFps);
lastQueuedPresentationTimeUs = C.TIME_UNSET;
previousPresentationTimeUs = C.TIME_UNSET;
}
@Override
public void queueInputFrame(GlTextureInfo inputTexture, long presentationTimeUs) {
if (previousTexture == null) {
super.queueInputFrame(inputTexture, presentationTimeUs);
lastQueuedPresentationTimeUs = presentationTimeUs;
isPreviousFrameFirstFrame = true;
} else if (shouldQueuePreviousFrame(presentationTimeUs)) {
super.queueInputFrame(checkNotNull(previousTexture), previousPresentationTimeUs);
lastQueuedPresentationTimeUs = previousPresentationTimeUs;
} else {
inputListener.onInputFrameProcessed(checkNotNull(previousTexture));
inputListener.onReadyToAcceptInputFrame();
}
previousTexture = inputTexture;
previousPresentationTimeUs = presentationTimeUs;
}
@Override
public void flush() {
super.flush();
lastQueuedPresentationTimeUs = C.TIME_UNSET;
previousPresentationTimeUs = C.TIME_UNSET;
previousTexture = null;
}
private boolean shouldQueuePreviousFrame(long currentPresentationTimeUs) {
if (isPreviousFrameFirstFrame) {
isPreviousFrameFirstFrame = false;
return false;
}
long previousFrameTimeDeltaUs = previousPresentationTimeUs - lastQueuedPresentationTimeUs;
long currentFrameTimeDeltaUs = currentPresentationTimeUs - lastQueuedPresentationTimeUs;
return abs(previousFrameTimeDeltaUs - targetFrameDeltaUs)
< abs(currentFrameTimeDeltaUs - targetFrameDeltaUs);
}
}