content: /*
   * 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
   */
  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);
  
      private static final AudioCodec[] sCodecs = {GSM_EFR, AMR, 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);
      }
  }
  