BoxUtils.java
/*
* Copyright 2022 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.muxer;
import com.google.common.base.Charsets;
import java.nio.ByteBuffer;
import java.util.List;
/** Utilities for dealing with MP4 boxes. */
/* package */ final class BoxUtils {
private static final int BOX_TYPE_BYTES = 4;
private static final int BOX_SIZE_BYTES = 4;
private BoxUtils() {}
/** Wraps content into a box, prefixing it with a length and a box type. */
public static ByteBuffer wrapIntoBox(String boxType, ByteBuffer contents) {
byte[] typeByteArray = boxType.getBytes(Charsets.UTF_8);
return wrapIntoBox(typeByteArray, contents);
}
/**
* Wraps content into a box, prefixing it with a length and a box type.
*
* <p>Use this method for box types with special characters. For example location box, which has a
* copyright symbol in the beginning.
*/
public static ByteBuffer wrapIntoBox(byte[] boxType, ByteBuffer contents) {
ByteBuffer box = ByteBuffer.allocate(contents.remaining() + BOX_TYPE_BYTES + BOX_SIZE_BYTES);
box.putInt(contents.remaining() + BOX_TYPE_BYTES + BOX_SIZE_BYTES);
box.put(boxType, 0, BOX_SIZE_BYTES);
box.put(contents);
box.flip();
return box;
}
/** Concatenate multiple boxes into a box, prefixing it with a length and a box type. */
public static ByteBuffer wrapBoxesIntoBox(String boxType, List<ByteBuffer> boxes) {
int totalSize = BOX_TYPE_BYTES + BOX_SIZE_BYTES;
for (int i = 0; i < boxes.size(); i++) {
totalSize += boxes.get(i).limit();
}
ByteBuffer result = ByteBuffer.allocate(totalSize);
result.putInt(totalSize);
result.put(boxType.getBytes(Charsets.UTF_8), 0, BOX_TYPE_BYTES);
for (int i = 0; i < boxes.size(); i++) {
result.put(boxes.get(i));
}
result.flip();
return result;
}
/**
* Concatenates multiple {@linkplain ByteBuffer byte buffers} into a single {@link ByteBuffer}.
*/
public static ByteBuffer concatenateBuffers(ByteBuffer... buffers) {
int totalSize = 0;
for (ByteBuffer buffer : buffers) {
totalSize += buffer.limit();
}
ByteBuffer result = ByteBuffer.allocate(totalSize);
for (ByteBuffer buffer : buffers) {
result.put(buffer);
}
result.flip();
return result;
}
}