1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16package androidx.media.filterfw;
17
18import java.util.LinkedList;
19import java.util.Queue;
20
21/**
22 * A {@link Filter} that pushes out externally injected frames.
23 * <p> When a frame is injected using {@link #injectFrame(Frame)}, this source will push it on its
24 * output port and then sleep until another frame is injected.
25 * <p> Multiple frames may be injected before any frame is pushed out. In this case they will be
26 * queued and pushed in FIFO order.
27 */
28class FrameSourceFilter extends Filter {
29
30    private final Queue<Frame> mFrames = new LinkedList<Frame>();
31
32    FrameSourceFilter(MffContext context, String name) {
33        super(context, name);
34    }
35
36    @Override
37    public Signature getSignature() {
38        return new Signature()
39                .addOutputPort("output", Signature.PORT_REQUIRED, FrameType.any())
40                .disallowOtherPorts();
41    }
42
43    private synchronized Frame obtainFrame() {
44        if (mFrames.isEmpty()) {
45            enterSleepState();
46            return null;
47        } else {
48            return mFrames.poll();
49        }
50    }
51
52    /**
53     * Call this method to inject a frame that will be pushed in a future execution of the filter.
54     * <p> If multiple frames are injected then they will be pushed one per execution in FIFO order.
55     */
56    public synchronized void injectFrame(Frame frame) {
57        mFrames.add(frame);
58        wakeUp();
59    }
60
61    @Override
62    protected void onProcess() {
63        Frame frame = obtainFrame();
64        if (frame != null) {
65            getConnectedOutputPort("output").pushFrame(frame);
66        }
67    }
68
69}
70