148 lines
4.8 KiB
Java
148 lines
4.8 KiB
Java
/*
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* Copyright (C) 2010 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.net.rtp;
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import java.util.Arrays;
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/**
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* This class defines a collection of audio codecs to be used with
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* {@link AudioStream}s. Their parameters are designed to be exchanged using
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* Session Description Protocol (SDP). Most of the values listed here can be
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* found in RFC 3551, while others are described in separated standards.
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*
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* <p>Few simple configurations are defined as public static instances for the
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* convenience of direct uses. More complicated ones could be obtained using
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* {@link #getCodec(int, String, String)}. For example, one can use the
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* following snippet to create a mode-1-only AMR codec.</p>
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* <pre>
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* AudioCodec codec = AudioCodec.getCodec(100, "AMR/8000", "mode-set=1");
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* </pre>
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*
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* @see AudioStream
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* @hide
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*/
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public class AudioCodec {
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/**
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* The RTP payload type of the encoding.
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*/
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public final int type;
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/**
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* The encoding parameters to be used in the corresponding SDP attribute.
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*/
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public final String rtpmap;
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/**
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* The format parameters to be used in the corresponding SDP attribute.
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*/
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public final String fmtp;
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/**
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* G.711 u-law audio codec.
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*/
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public static final AudioCodec PCMU = new AudioCodec(0, "PCMU/8000", null);
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/**
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* G.711 a-law audio codec.
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*/
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public static final AudioCodec PCMA = new AudioCodec(8, "PCMA/8000", null);
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/**
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* GSM Full-Rate audio codec, also known as GSM-FR, GSM 06.10, GSM, or
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* simply FR.
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*/
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public static final AudioCodec GSM = new AudioCodec(3, "GSM/8000", null);
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/**
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* GSM Enhanced Full-Rate audio codec, also known as GSM-EFR, GSM 06.60, or
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* simply EFR.
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*/
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public static final AudioCodec GSM_EFR = new AudioCodec(96, "GSM-EFR/8000", null);
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/**
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* Adaptive Multi-Rate narrowband audio codec, also known as AMR or AMR-NB.
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* Currently CRC, robust sorting, and interleaving are not supported. See
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* more details about these features in RFC 4867.
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*/
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public static final AudioCodec AMR = new AudioCodec(97, "AMR/8000", null);
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private static final AudioCodec[] sCodecs = {GSM_EFR, AMR, GSM, PCMU, PCMA};
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private AudioCodec(int type, String rtpmap, String fmtp) {
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this.type = type;
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this.rtpmap = rtpmap;
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this.fmtp = fmtp;
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}
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/**
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* Returns system supported audio codecs.
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*/
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public static AudioCodec[] getCodecs() {
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return Arrays.copyOf(sCodecs, sCodecs.length);
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}
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/**
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* Creates an AudioCodec according to the given configuration.
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*
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* @param type The payload type of the encoding defined in RTP/AVP.
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* @param rtpmap The encoding parameters specified in the corresponding SDP
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* attribute, or null if it is not available.
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* @param fmtp The format parameters specified in the corresponding SDP
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* attribute, or null if it is not available.
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* @return The configured AudioCodec or {@code null} if it is not supported.
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*/
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public static AudioCodec getCodec(int type, String rtpmap, String fmtp) {
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if (type < 0 || type > 127) {
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return null;
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}
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AudioCodec hint = null;
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if (rtpmap != null) {
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String clue = rtpmap.trim().toUpperCase();
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for (AudioCodec codec : sCodecs) {
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if (clue.startsWith(codec.rtpmap)) {
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String channels = clue.substring(codec.rtpmap.length());
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if (channels.length() == 0 || channels.equals("/1")) {
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hint = codec;
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}
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break;
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}
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}
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} else if (type < 96) {
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for (AudioCodec codec : sCodecs) {
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if (type == codec.type) {
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hint = codec;
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rtpmap = codec.rtpmap;
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break;
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}
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}
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}
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if (hint == null) {
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return null;
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}
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if (hint == AMR && fmtp != null) {
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String clue = fmtp.toLowerCase();
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if (clue.contains("crc=1") || clue.contains("robust-sorting=1") ||
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clue.contains("interleaving=")) {
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return null;
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}
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}
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return new AudioCodec(type, rtpmap, fmtp);
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}
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}
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