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 "modules/audio_coding/neteq/timestamp_scaler.h" 12 13 #include "api/audio_codecs/audio_format.h" 14 #include "modules/audio_coding/neteq/decoder_database.h" 15 #include "rtc_base/checks.h" 16 17 namespace webrtc { 18 Reset()19void TimestampScaler::Reset() { 20 first_packet_received_ = false; 21 } 22 ToInternal(Packet * packet)23void TimestampScaler::ToInternal(Packet* packet) { 24 if (!packet) { 25 return; 26 } 27 packet->timestamp = ToInternal(packet->timestamp, packet->payload_type); 28 } 29 ToInternal(PacketList * packet_list)30void TimestampScaler::ToInternal(PacketList* packet_list) { 31 PacketList::iterator it; 32 for (it = packet_list->begin(); it != packet_list->end(); ++it) { 33 ToInternal(&(*it)); 34 } 35 } 36 ToInternal(uint32_t external_timestamp,uint8_t rtp_payload_type)37uint32_t TimestampScaler::ToInternal(uint32_t external_timestamp, 38 uint8_t rtp_payload_type) { 39 const DecoderDatabase::DecoderInfo* info = 40 decoder_database_.GetDecoderInfo(rtp_payload_type); 41 if (!info) { 42 // Payload type is unknown. Do not scale. 43 return external_timestamp; 44 } 45 if (!(info->IsComfortNoise() || info->IsDtmf())) { 46 // Do not change the timestamp scaling settings for DTMF or CNG. 47 numerator_ = info->SampleRateHz(); 48 if (info->GetFormat().clockrate_hz == 0) { 49 // If the clockrate is invalid (i.e. with an old-style external codec) 50 // we cannot do any timestamp scaling. 51 denominator_ = numerator_; 52 } else { 53 denominator_ = info->GetFormat().clockrate_hz; 54 } 55 } 56 if (numerator_ != denominator_) { 57 // We have a scale factor != 1. 58 if (!first_packet_received_) { 59 external_ref_ = external_timestamp; 60 internal_ref_ = external_timestamp; 61 first_packet_received_ = true; 62 } 63 const int64_t external_diff = int64_t{external_timestamp} - external_ref_; 64 RTC_DCHECK_GT(denominator_, 0); 65 external_ref_ = external_timestamp; 66 internal_ref_ += (external_diff * numerator_) / denominator_; 67 return internal_ref_; 68 } else { 69 // No scaling. 70 return external_timestamp; 71 } 72 } 73 ToExternal(uint32_t internal_timestamp) const74uint32_t TimestampScaler::ToExternal(uint32_t internal_timestamp) const { 75 if (!first_packet_received_ || (numerator_ == denominator_)) { 76 // Not initialized, or scale factor is 1. 77 return internal_timestamp; 78 } else { 79 const int64_t internal_diff = int64_t{internal_timestamp} - internal_ref_; 80 RTC_DCHECK_GT(numerator_, 0); 81 // Do not update references in this method. 82 // Switch |denominator_| and |numerator_| to convert the other way. 83 return external_ref_ + (internal_diff * denominator_) / numerator_; 84 } 85 } 86 87 } // namespace webrtc 88