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      1 /*
      2  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #include "webrtc/modules/audio_coding/neteq/timestamp_scaler.h"
     12 
     13 #include "webrtc/modules/audio_coding/neteq/decoder_database.h"
     14 #include "webrtc/modules/audio_coding/neteq/defines.h"
     15 #include "webrtc/system_wrappers/include/logging.h"
     16 
     17 namespace webrtc {
     18 
     19 void TimestampScaler::Reset() {
     20   first_packet_received_ = false;
     21 }
     22 
     23 void TimestampScaler::ToInternal(Packet* packet) {
     24   if (!packet) {
     25     return;
     26   }
     27   packet->header.timestamp = ToInternal(packet->header.timestamp,
     28                                         packet->header.payloadType);
     29 }
     30 
     31 void TimestampScaler::ToInternal(PacketList* packet_list) {
     32   PacketList::iterator it;
     33   for (it = packet_list->begin(); it != packet_list->end(); ++it) {
     34     ToInternal(*it);
     35   }
     36 }
     37 
     38 uint32_t TimestampScaler::ToInternal(uint32_t external_timestamp,
     39                                      uint8_t rtp_payload_type) {
     40   const DecoderDatabase::DecoderInfo* info =
     41       decoder_database_.GetDecoderInfo(rtp_payload_type);
     42   if (!info) {
     43     // Payload type is unknown. Do not scale.
     44     return external_timestamp;
     45   }
     46   switch (info->codec_type) {
     47     case NetEqDecoder::kDecoderG722:
     48     case NetEqDecoder::kDecoderG722_2ch: {
     49       // Use timestamp scaling with factor 2 (two output samples per RTP
     50       // timestamp).
     51       numerator_ = 2;
     52       denominator_ = 1;
     53       break;
     54     }
     55     case NetEqDecoder::kDecoderAVT:
     56     case NetEqDecoder::kDecoderCNGnb:
     57     case NetEqDecoder::kDecoderCNGwb:
     58     case NetEqDecoder::kDecoderCNGswb32kHz:
     59     case NetEqDecoder::kDecoderCNGswb48kHz: {
     60       // Do not change the timestamp scaling settings for DTMF or CNG.
     61       break;
     62     }
     63     default: {
     64       // Do not use timestamp scaling for any other codec.
     65       numerator_ = 1;
     66       denominator_ = 1;
     67       break;
     68     }
     69   }
     70 
     71   if (!(numerator_ == 1 && denominator_ == 1)) {
     72     // We have a scale factor != 1.
     73     if (!first_packet_received_) {
     74       external_ref_ = external_timestamp;
     75       internal_ref_ = external_timestamp;
     76       first_packet_received_ = true;
     77     }
     78     int32_t external_diff = external_timestamp - external_ref_;
     79     assert(denominator_ > 0);  // Should not be possible.
     80     external_ref_ = external_timestamp;
     81     internal_ref_ += (external_diff * numerator_) / denominator_;
     82     return internal_ref_;
     83   } else {
     84     // No scaling.
     85     return external_timestamp;
     86   }
     87 }
     88 
     89 
     90 uint32_t TimestampScaler::ToExternal(uint32_t internal_timestamp) const {
     91   if (!first_packet_received_ || (numerator_ == 1 && denominator_ == 1)) {
     92     // Not initialized, or scale factor is 1.
     93     return internal_timestamp;
     94   } else {
     95     int32_t internal_diff = internal_timestamp - internal_ref_;
     96     assert(numerator_ > 0);  // Should not be possible.
     97     // Do not update references in this method.
     98     // Switch |denominator_| and |numerator_| to convert the other way.
     99     return external_ref_ + (internal_diff * denominator_) / numerator_;
    100   }
    101 }
    102 
    103 }  // namespace webrtc
    104