media/formats/webm/opus_packet_builder.cc

   1 // Copyright (c) 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/logging.h"
   6 #include "media/formats/webm/opus_packet_builder.h"
   7 #include "media/formats/webm/webm_cluster_parser.h"
   8
   9 namespace media {
  10
  11 OpusPacket::OpusPacket(uint8_t config, uint8_t frame_count, bool is_VBR) {
  12   DCHECK_GE(config, 0);
  13   DCHECK_LT(config, kNumPossibleOpusConfigs);
  14   DCHECK_GE(frame_count, kMinOpusPacketFrameCount);
  15   DCHECK_LE(frame_count, kMaxOpusPacketFrameCount);
  16
  17   duration_ms_ = frame_count *
  18                  WebMClusterParser::kOpusFrameDurationsMu[config] /
  19                  static_cast<float>(1000);
  20
  21   uint8_t frame_count_code;
  22   uint8_t frame_count_byte;
  23
  24   if (frame_count == 1) {
  25     frame_count_code = 0;
  26   } else if (frame_count == 2) {
  27     frame_count_code = is_VBR ? 2 : 1;
  28   } else {
  29     frame_count_code = 3;
  30     frame_count_byte = (is_VBR ? 1 << 7 : 0) | frame_count;
  31   }
  32
  33   // All opus packets must have TOC byte.
  34   uint8_t opus_toc_byte = (config << 3) | frame_count_code;
  35   data_.push_back(opus_toc_byte);
  36
  37   // For code 3 packets, the number of frames is signaled in the "frame
  38   // count byte".
  39   if (frame_count_code == 3) {
  40     data_.push_back(frame_count_byte);
  41   }
  42
  43   // Packet will only conform to layout specification for the TOC byte
  44   // and optional frame count bytes appended above. This last byte
  45   // is purely dummy padding where frame size data or encoded data might
  46   // otherwise start.
  47   data_.push_back(static_cast<uint8_t>(0));
  48 }
  49
  50 OpusPacket::~OpusPacket() {
  51 }
  52
  53 const uint8_t* OpusPacket::data() const {
  54   return &(data_[0]);
  55 }
  56
  57 int OpusPacket::size() const {
  58   return data_.size();
  59 }
  60
  61 double OpusPacket::duration_ms() const {
  62   return duration_ms_;
  63 }
  64
  65 ScopedVector<OpusPacket> BuildAllOpusPackets() {
  66   ScopedVector<OpusPacket> opus_packets;
  67
  68   for (int frame_count = kMinOpusPacketFrameCount;
  69        frame_count <= kMaxOpusPacketFrameCount; frame_count++) {
  70     for (int opus_config_num = 0; opus_config_num < kNumPossibleOpusConfigs;
  71          opus_config_num++) {
  72       bool is_VBR = false;
  73       opus_packets.push_back(
  74           new OpusPacket(opus_config_num, frame_count, is_VBR));
  75
  76       if (frame_count >= 2) {
  77         // Add another packet with VBR flag toggled. For frame counts >= 2,
  78         // VBR triggers changes to packet framing.
  79         is_VBR = true;
  80         opus_packets.push_back(
  81             new OpusPacket(opus_config_num, frame_count, is_VBR));
  82       }
  83     }
  84   }
  85
  86   return opus_packets.Pass();
  87 }
  88
  89 }  // namespace media