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/*
* Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "modules/audio_coding/neteq/timestamp_scaler.h"
#include "api/audio_codecs/audio_format.h"
#include "modules/audio_coding/neteq/decoder_database.h"
#include "rtc_base/checks.h"
namespace webrtc {
void TimestampScaler::Reset() {
first_packet_received_ = false;
}
void TimestampScaler::ToInternal(Packet* packet) {
if (!packet) {
return;
}
packet->timestamp = ToInternal(packet->timestamp, packet->payload_type);
}
void TimestampScaler::ToInternal(PacketList* packet_list) {
PacketList::iterator it;
for (it = packet_list->begin(); it != packet_list->end(); ++it) {
ToInternal(&(*it));
}
}
uint32_t TimestampScaler::ToInternal(uint32_t external_timestamp,
uint8_t rtp_payload_type) {
const DecoderDatabase::DecoderInfo* info =
decoder_database_.GetDecoderInfo(rtp_payload_type);
if (!info) {
// Payload type is unknown. Do not scale.
return external_timestamp;
}
if (!(info->IsComfortNoise() || info->IsDtmf())) {
// Do not change the timestamp scaling settings for DTMF or CNG.
numerator_ = info->SampleRateHz();
if (info->GetFormat().clockrate_hz == 0) {
// If the clockrate is invalid (i.e. with an old-style external codec)
// we cannot do any timestamp scaling.
denominator_ = numerator_;
} else {
denominator_ = info->GetFormat().clockrate_hz;
}
}
if (numerator_ != denominator_) {
// We have a scale factor != 1.
if (!first_packet_received_) {
external_ref_ = external_timestamp;
internal_ref_ = external_timestamp;
first_packet_received_ = true;
}
const int64_t external_diff = int64_t{external_timestamp} - external_ref_;
RTC_DCHECK_GT(denominator_, 0);
external_ref_ = external_timestamp;
internal_ref_ += (external_diff * numerator_) / denominator_;
return internal_ref_;
} else {
// No scaling.
return external_timestamp;
}
}
uint32_t TimestampScaler::ToExternal(uint32_t internal_timestamp) const {
if (!first_packet_received_ || (numerator_ == denominator_)) {
// Not initialized, or scale factor is 1.
return internal_timestamp;
} else {
const int64_t internal_diff = int64_t{internal_timestamp} - internal_ref_;
RTC_DCHECK_GT(numerator_, 0);
// Do not update references in this method.
// Switch `denominator_` and `numerator_` to convert the other way.
return external_ref_ + (internal_diff * denominator_) / numerator_;
}
}
} // namespace webrtc
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