120 lines
5.0 KiB
C++
120 lines
5.0 KiB
C++
// Copyright 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef CAST_STREAMING_CONSTANTS_H_
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#define CAST_STREAMING_CONSTANTS_H_
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////////////////////////////////////////////////////////////////////////////////
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// NOTE: This file should only contain constants that are reasonably globally
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// used (i.e., by many modules, and in all or nearly all subdirs). Do NOT add
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// non-POD constants, functions, interfaces, or any logic to this module.
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////////////////////////////////////////////////////////////////////////////////
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#include <chrono>
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#include <ratio>
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namespace openscreen {
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namespace cast {
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// Mirroring App identifier.
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constexpr char kMirroringAppId[] = "0F5096E8";
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// Mirroring App identifier for audio-only mirroring.
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constexpr char kMirroringAudioOnlyAppId[] = "85CDB22F";
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// Default target playout delay. The playout delay is the window of time between
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// capture from the source until presentation at the receiver.
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constexpr std::chrono::milliseconds kDefaultTargetPlayoutDelay(400);
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// Default UDP port, bound at the Receiver, for Cast Streaming. An
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// implementation is required to use the port specified by the Receiver in its
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// ANSWER control message, which may or may not match this port number here.
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constexpr int kDefaultCastStreamingPort = 2344;
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// Default TCP port, bound at the TLS server socket level, for Cast Streaming.
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// An implementation must use the port specified in the DNS-SD published record
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// for connecting over TLS, which may or may not match this port number here.
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constexpr int kDefaultCastPort = 8010;
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// Target number of milliseconds between the sending of RTCP reports. Both
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// senders and receivers regularly send RTCP reports to their peer.
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constexpr std::chrono::milliseconds kRtcpReportInterval(500);
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// This is an important system-wide constant. This limits how much history
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// the implementation must retain in order to process the acknowledgements of
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// past frames.
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//
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// This value is carefully choosen such that it fits in the 8-bits range for
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// frame IDs. It is also less than half of the full 8-bits range such that
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// logic can handle wrap around and compare two frame IDs meaningfully.
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constexpr int kMaxUnackedFrames = 120;
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// The network must support a packet size of at least this many bytes.
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constexpr int kRequiredNetworkPacketSize = 256;
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// The spec declares RTP timestamps must always have a timebase of 90000 ticks
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// per second for video.
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constexpr int kRtpVideoTimebase = 90000;
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// Minimum resolution is 320x240.
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constexpr int kMinVideoHeight = 240;
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constexpr int kMinVideoWidth = 320;
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// The default frame rate for capture options is 30FPS.
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constexpr int kDefaultFrameRate = 30;
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// The mirroring spec suggests 300kbps as the absolute minimum bitrate.
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constexpr int kDefaultVideoMinBitRate = 300 * 1000;
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// Default video max bitrate is based on 1080P @ 30FPS, which can be played back
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// at good quality around 10mbps.
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constexpr int kDefaultVideoMaxBitRate = 10 * 1000 * 1000;
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// The mirroring control protocol specifies 32kbps as the absolute minimum
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// for audio. Depending on the type of audio content (narrowband, fullband,
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// etc.) Opus specifically can perform very well at this bitrate.
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// See: https://research.google/pubs/pub41650/
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constexpr int kDefaultAudioMinBitRate = 32 * 1000;
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// Opus generally sees little improvement above 192kbps, but some older codecs
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// that we may consider supporting improve at up to 256kbps.
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constexpr int kDefaultAudioMaxBitRate = 256 * 1000;
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// While generally audio should be captured at the maximum sample rate, 16kHz is
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// the recommended absolute minimum.
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constexpr int kDefaultAudioMinSampleRate = 16000;
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// The default audio sample rate is 48kHz, slightly higher than standard
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// consumer audio.
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constexpr int kDefaultAudioSampleRate = 48000;
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// The default audio number of channels is set to stereo.
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constexpr int kDefaultAudioChannels = 2;
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// Default maximum delay for both audio and video. Used if the sender fails
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// to provide any constraints.
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constexpr std::chrono::milliseconds kDefaultMaxDelayMs(1500);
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// TODO(issuetracker.google.com/184189100): As part of updating remoting
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// OFFER/ANSWER and capabilities exchange, remoting version should be updated
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// to 3.
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constexpr int kSupportedRemotingVersion = 2;
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// Codecs known and understood by cast senders and receivers. Note: receivers
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// are required to implement the following codecs to be Cast V2 compliant: H264,
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// VP8, AAC, Opus. Senders have to implement at least one codec from this
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// list for audio or video to start a session.
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// |kNotSpecified| is used in remoting to indicate that the stream is being
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// remoted and is not specified as part of the OFFER message (indicated as
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// "REMOTE_AUDIO" or "REMOTE_VIDEO").
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enum class AudioCodec { kAac, kOpus, kNotSpecified };
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enum class VideoCodec { kH264, kVp8, kHevc, kNotSpecified, kVp9, kAv1 };
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enum class CastMode : uint8_t { kMirroring, kRemoting };
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} // namespace cast
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} // namespace openscreen
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#endif // CAST_STREAMING_CONSTANTS_H_
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