tor-browser

The Tor Browser
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timestamp_scaler.cc (2986B)

      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 <cstdint>
     14 
     15 #include "api/audio_codecs/audio_format.h"
     16 #include "modules/audio_coding/neteq/decoder_database.h"
     17 #include "modules/audio_coding/neteq/packet.h"
     18 #include "rtc_base/checks.h"
     19 
     20 namespace webrtc {
     21 
     22 void TimestampScaler::Reset() {
     23  first_packet_received_ = false;
     24 }
     25 
     26 void TimestampScaler::ToInternal(Packet* packet) {
     27  if (!packet) {
     28    return;
     29  }
     30  packet->timestamp = ToInternal(packet->timestamp, packet->payload_type);
     31 }
     32 
     33 void TimestampScaler::ToInternal(PacketList* packet_list) {
     34  PacketList::iterator it;
     35  for (it = packet_list->begin(); it != packet_list->end(); ++it) {
     36    ToInternal(&(*it));
     37  }
     38 }
     39 
     40 uint32_t TimestampScaler::ToInternal(uint32_t external_timestamp,
     41                                     uint8_t rtp_payload_type) {
     42  const DecoderDatabase::DecoderInfo* info =
     43      decoder_database_.GetDecoderInfo(rtp_payload_type);
     44  if (!info) {
     45    // Payload type is unknown. Do not scale.
     46    return external_timestamp;
     47  }
     48  if (!(info->IsComfortNoise() || info->IsDtmf())) {
     49    // Do not change the timestamp scaling settings for DTMF or CNG.
     50    numerator_ = info->SampleRateHz();
     51    if (info->GetFormat().clockrate_hz == 0) {
     52      // If the clockrate is invalid (i.e. with an old-style external codec)
     53      // we cannot do any timestamp scaling.
     54      denominator_ = numerator_;
     55    } else {
     56      denominator_ = info->GetFormat().clockrate_hz;
     57    }
     58  }
     59  if (numerator_ != denominator_) {
     60    // We have a scale factor != 1.
     61    if (!first_packet_received_) {
     62      external_ref_ = external_timestamp;
     63      internal_ref_ = external_timestamp;
     64      first_packet_received_ = true;
     65    }
     66    const int64_t external_diff = int64_t{external_timestamp} - external_ref_;
     67    RTC_DCHECK_GT(denominator_, 0);
     68    external_ref_ = external_timestamp;
     69    internal_ref_ += (external_diff * numerator_) / denominator_;
     70    return internal_ref_;
     71  } else {
     72    // No scaling.
     73    return external_timestamp;
     74  }
     75 }
     76 
     77 uint32_t TimestampScaler::ToExternal(uint32_t internal_timestamp) const {
     78  if (!first_packet_received_ || (numerator_ == denominator_)) {
     79    // Not initialized, or scale factor is 1.
     80    return internal_timestamp;
     81  } else {
     82    const int64_t internal_diff = int64_t{internal_timestamp} - internal_ref_;
     83    RTC_DCHECK_GT(numerator_, 0);
     84    // Do not update references in this method.
     85    // Switch `denominator_` and `numerator_` to convert the other way.
     86    return external_ref_ + (internal_diff * denominator_) / numerator_;
     87  }
     88 }
     89 
     90 }  // namespace webrtc