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/*
* Copyright (C) 2010 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 android.net.rtp;
import java.util.Arrays;
/**
* This class defines a collection of audio codecs to be used with
* {@link AudioStream}s. Their parameters are designed to be exchanged using
* Session Description Protocol (SDP). Most of the values listed here can be
* found in RFC 3551, while others are described in separated standards.
*
* <p>Few simple configurations are defined as public static instances for the
* convenience of direct uses. More complicated ones could be obtained using
* {@link #getCodec(int, String, String)}. For example, one can use the
* following snippet to create a mode-1-only AMR codec.</p>
* <pre>
* AudioCodec codec = AudioCodec.getCodec(100, "AMR/8000", "mode-set=1");
* </pre>
*
* @see AudioStream
* @hide
*/
public class AudioCodec {
/**
* The RTP payload type of the encoding.
*/
public final int type;
/**
* The encoding parameters to be used in the corresponding SDP attribute.
*/
public final String rtpmap;
/**
* The format parameters to be used in the corresponding SDP attribute.
*/
public final String fmtp;
/**
* G.711 u-law audio codec.
*/
public static final AudioCodec PCMU = new AudioCodec(0, "PCMU/8000", null);
/**
* G.711 a-law audio codec.
*/
public static final AudioCodec PCMA = new AudioCodec(8, "PCMA/8000", null);
/**
* GSM Full-Rate audio codec, also known as GSM-FR, GSM 06.10, GSM, or
* simply FR.
*/
public static final AudioCodec GSM = new AudioCodec(3, "GSM/8000", null);
/**
* GSM Enhanced Full-Rate audio codec, also known as GSM-EFR, GSM 06.60, or
* simply EFR.
*/
public static final AudioCodec GSM_EFR = new AudioCodec(96, "GSM-EFR/8000", null);
/**
* Adaptive Multi-Rate narrowband audio codec, also known as AMR or AMR-NB.
* Currently CRC, robust sorting, and interleaving are not supported. See
* more details about these features in RFC 4867.
*/
public static final AudioCodec AMR = new AudioCodec(97, "AMR/8000", null);
// TODO: add rest of the codecs when the native part is done.
private static final AudioCodec[] sCodecs = {GSM, PCMU, PCMA};
private AudioCodec(int type, String rtpmap, String fmtp) {
this.type = type;
this.rtpmap = rtpmap;
this.fmtp = fmtp;
}
/**
* Returns system supported audio codecs.
*/
public static AudioCodec[] getCodecs() {
return Arrays.copyOf(sCodecs, sCodecs.length);
}
/**
* Creates an AudioCodec according to the given configuration.
*
* @param type The payload type of the encoding defined in RTP/AVP.
* @param rtpmap The encoding parameters specified in the corresponding SDP
* attribute, or null if it is not available.
* @param fmtp The format parameters specified in the corresponding SDP
* attribute, or null if it is not available.
* @return The configured AudioCodec or {@code null} if it is not supported.
*/
public static AudioCodec getCodec(int type, String rtpmap, String fmtp) {
if (type < 0 || type > 127) {
return null;
}
AudioCodec hint = null;
if (rtpmap != null) {
String clue = rtpmap.trim().toUpperCase();
for (AudioCodec codec : sCodecs) {
if (clue.startsWith(codec.rtpmap)) {
String channels = clue.substring(codec.rtpmap.length());
if (channels.length() == 0 || channels.equals("/1")) {
hint = codec;
}
break;
}
}
} else if (type < 96) {
for (AudioCodec codec : sCodecs) {
if (type == codec.type) {
hint = codec;
rtpmap = codec.rtpmap;
break;
}
}
}
if (hint == null) {
return null;
}
if (hint == AMR && fmtp != null) {
String clue = fmtp.toLowerCase();
if (clue.contains("crc=1") || clue.contains("robust-sorting=1") ||
clue.contains("interleaving=")) {
return null;
}
}
return new AudioCodec(type, rtpmap, fmtp);
}
}
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