| /* |
| * 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 "webrtc/modules/audio_coding/neteq/dtmf_buffer.h" |
| |
| #include <assert.h> |
| #include <algorithm> // max |
| |
| #include "webrtc/base/checks.h" |
| #include "webrtc/base/logging.h" |
| |
| // Modify the code to obtain backwards bit-exactness. Once bit-exactness is no |
| // longer required, this #define should be removed (and the code that it |
| // enables). |
| #define LEGACY_BITEXACT |
| |
| namespace webrtc { |
| |
| DtmfBuffer::DtmfBuffer(int fs_hz) { |
| SetSampleRate(fs_hz); |
| } |
| |
| DtmfBuffer::~DtmfBuffer() = default; |
| |
| void DtmfBuffer::Flush() { |
| buffer_.clear(); |
| } |
| |
| // The ParseEvent method parses 4 bytes from |payload| according to this format |
| // from RFC 4733: |
| // |
| // 0 1 2 3 |
| // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| // | event |E|R| volume | duration | |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| // |
| // Legend (adapted from RFC 4733) |
| // - event: The event field is a number between 0 and 255 identifying a |
| // specific telephony event. The buffer will not accept any event |
| // numbers larger than 15. |
| // - E: If set to a value of one, the "end" bit indicates that this |
| // packet contains the end of the event. For long-lasting events |
| // that have to be split into segments, only the final packet for |
| // the final segment will have the E bit set. |
| // - R: Reserved. |
| // - volume: For DTMF digits and other events representable as tones, this |
| // field describes the power level of the tone, expressed in dBm0 |
| // after dropping the sign. Power levels range from 0 to -63 dBm0. |
| // Thus, larger values denote lower volume. The buffer discards |
| // values larger than 36 (i.e., lower than -36 dBm0). |
| // - duration: The duration field indicates the duration of the event or segment |
| // being reported, in timestamp units, expressed as an unsigned |
| // integer in network byte order. For a non-zero value, the event |
| // or segment began at the instant identified by the RTP timestamp |
| // and has so far lasted as long as indicated by this parameter. |
| // The event may or may not have ended. If the event duration |
| // exceeds the maximum representable by the duration field, the |
| // event is split into several contiguous segments. The buffer will |
| // discard zero-duration events. |
| // |
| int DtmfBuffer::ParseEvent(uint32_t rtp_timestamp, |
| const uint8_t* payload, |
| size_t payload_length_bytes, |
| DtmfEvent* event) { |
| RTC_CHECK(payload); |
| RTC_CHECK(event); |
| if (payload_length_bytes < 4) { |
| LOG(LS_WARNING) << "ParseEvent payload too short"; |
| return kPayloadTooShort; |
| } |
| |
| event->event_no = payload[0]; |
| event->end_bit = ((payload[1] & 0x80) != 0); |
| event->volume = (payload[1] & 0x3F); |
| event->duration = payload[2] << 8 | payload[3]; |
| event->timestamp = rtp_timestamp; |
| return kOK; |
| } |
| |
| // Inserts a DTMF event into the buffer. The event should be parsed from the |
| // bit stream using the ParseEvent method above before inserting it in the |
| // buffer. |
| // DTMF events can be quite long, and in most cases the duration of the event |
| // is not known when the first packet describing it is sent. To deal with that, |
| // the RFC 4733 specifies that multiple packets are sent for one and the same |
| // event as it is being created (typically, as the user is pressing the key). |
| // These packets will all share the same start timestamp and event number, |
| // while the duration will be the cumulative duration from the start. When |
| // inserting a new event, the InsertEvent method tries to find a matching event |
| // already in the buffer. If so, the new event is simply merged with the |
| // existing one. |
| int DtmfBuffer::InsertEvent(const DtmfEvent& event) { |
| if (event.event_no < 0 || event.event_no > 15 || |
| event.volume < 0 || event.volume > 36 || |
| event.duration <= 0 || event.duration > 65535) { |
| LOG(LS_WARNING) << "InsertEvent invalid parameters"; |
| return kInvalidEventParameters; |
| } |
| DtmfList::iterator it = buffer_.begin(); |
| while (it != buffer_.end()) { |
| if (MergeEvents(it, event)) { |
| // A matching event was found and the new event was merged. |
| return kOK; |
| } |
| ++it; |
| } |
| buffer_.push_back(event); |
| // Sort the buffer using CompareEvents to rank the events. |
| buffer_.sort(CompareEvents); |
| return kOK; |
| } |
| |
| bool DtmfBuffer::GetEvent(uint32_t current_timestamp, DtmfEvent* event) { |
| DtmfList::iterator it = buffer_.begin(); |
| while (it != buffer_.end()) { |
| // |event_end| is an estimate of where the current event ends. If the end |
| // bit is set, we know that the event ends at |timestamp| + |duration|. |
| uint32_t event_end = it->timestamp + it->duration; |
| #ifdef LEGACY_BITEXACT |
| bool next_available = false; |
| #endif |
| if (!it->end_bit) { |
| // If the end bit is not set, we allow extrapolation of the event for |
| // some time. |
| event_end += max_extrapolation_samples_; |
| DtmfList::iterator next = it; |
| ++next; |
| if (next != buffer_.end()) { |
| // If there is a next event in the buffer, we will not extrapolate over |
| // the start of that new event. |
| event_end = std::min(event_end, next->timestamp); |
| #ifdef LEGACY_BITEXACT |
| next_available = true; |
| #endif |
| } |
| } |
| if (current_timestamp >= it->timestamp |
| && current_timestamp <= event_end) { // TODO(hlundin): Change to <. |
| // Found a matching event. |
| if (event) { |
| event->event_no = it->event_no; |
| event->end_bit = it->end_bit; |
| event->volume = it->volume; |
| event->duration = it->duration; |
| event->timestamp = it->timestamp; |
| } |
| #ifdef LEGACY_BITEXACT |
| if (it->end_bit && |
| current_timestamp + frame_len_samples_ >= event_end) { |
| // We are done playing this. Erase the event. |
| buffer_.erase(it); |
| } |
| #endif |
| return true; |
| } else if (current_timestamp > event_end) { // TODO(hlundin): Change to >=. |
| // Erase old event. Operation returns a valid pointer to the next element |
| // in the list. |
| #ifdef LEGACY_BITEXACT |
| if (!next_available) { |
| if (event) { |
| event->event_no = it->event_no; |
| event->end_bit = it->end_bit; |
| event->volume = it->volume; |
| event->duration = it->duration; |
| event->timestamp = it->timestamp; |
| } |
| it = buffer_.erase(it); |
| return true; |
| } else { |
| it = buffer_.erase(it); |
| } |
| #else |
| it = buffer_.erase(it); |
| #endif |
| } else { |
| ++it; |
| } |
| } |
| return false; |
| } |
| |
| size_t DtmfBuffer::Length() const { |
| return buffer_.size(); |
| } |
| |
| bool DtmfBuffer::Empty() const { |
| return buffer_.empty(); |
| } |
| |
| int DtmfBuffer::SetSampleRate(int fs_hz) { |
| if (fs_hz != 8000 && |
| fs_hz != 16000 && |
| fs_hz != 32000 && |
| fs_hz != 48000) { |
| return kInvalidSampleRate; |
| } |
| max_extrapolation_samples_ = 7 * fs_hz / 100; |
| frame_len_samples_ = fs_hz / 100; |
| return kOK; |
| } |
| |
| // The method returns true if the two events are considered to be the same. |
| // The are defined as equal if they share the same timestamp and event number. |
| // The special case with long-lasting events that have to be split into segments |
| // is not handled in this method. These will be treated as separate events in |
| // the buffer. |
| bool DtmfBuffer::SameEvent(const DtmfEvent& a, const DtmfEvent& b) { |
| return (a.event_no == b.event_no) && (a.timestamp == b.timestamp); |
| } |
| |
| bool DtmfBuffer::MergeEvents(DtmfList::iterator it, const DtmfEvent& event) { |
| if (SameEvent(*it, event)) { |
| if (!it->end_bit) { |
| // Do not extend the duration of an event for which the end bit was |
| // already received. |
| it->duration = std::max(event.duration, it->duration); |
| } |
| if (event.end_bit) { |
| it->end_bit = true; |
| } |
| return true; |
| } else { |
| return false; |
| } |
| } |
| |
| // Returns true if |a| goes before |b| in the sorting order ("|a| < |b|"). |
| // The events are ranked using their start timestamp (taking wrap-around into |
| // account). In the unlikely situation that two events share the same start |
| // timestamp, the event number is used to rank the two. Note that packets |
| // that belong to the same events, and therefore sharing the same start |
| // timestamp, have already been merged before the sort method is called. |
| bool DtmfBuffer::CompareEvents(const DtmfEvent& a, const DtmfEvent& b) { |
| if (a.timestamp == b.timestamp) { |
| return a.event_no < b.event_no; |
| } |
| // Take wrap-around into account. |
| return (static_cast<uint32_t>(b.timestamp - a.timestamp) < 0xFFFFFFFF / 2); |
| } |
| } // namespace webrtc |