tor-browser

vp8_frame_buffer_controller.h (8233B)

---

/*
*  Copyright (c) 2019 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.
*/

#ifndef API_VIDEO_CODECS_VP8_FRAME_BUFFER_CONTROLLER_H_
#define API_VIDEO_CODECS_VP8_FRAME_BUFFER_CONTROLLER_H_

#include <array>
#include <cstddef>
#include <cstdint>
#include <memory>
#include <optional>
#include <vector>

#include "api/environment/environment.h"
#include "api/fec_controller_override.h"
#include "api/video_codecs/video_codec.h"
#include "api/video_codecs/video_encoder.h"
#include "api/video_codecs/vp8_frame_config.h"

namespace webrtc {

// Some notes on the prerequisites of the TemporalLayers interface.
// * Vp8FrameBufferController is not thread safe, synchronization is the
//   caller's responsibility.
// * The encoder is assumed to encode all frames in order, and callbacks to
//   PopulateCodecSpecific() / OnEncodeDone() must happen in the same order.
//
// This means that in the case of pipelining encoders, it is OK to have a chain
// of calls such as this:
// - NextFrameConfig(timestampA)
// - NextFrameConfig(timestampB)
// - PopulateCodecSpecific(timestampA, ...)
// - NextFrameConfig(timestampC)
// - OnEncodeDone(timestampA, 1234, ...)
// - NextFrameConfig(timestampC)
// - OnEncodeDone(timestampB, 0, ...)
// - OnEncodeDone(timestampC, 1234, ...)
// Note that NextFrameConfig() for a new frame can happen before
// OnEncodeDone() for a previous one, but calls themselves must be both
// synchronized (e.g. run on a task queue) and in order (per type).
//
// TODO(eladalon): Revise comment (referring to PopulateCodecSpecific in this
// context is not very meaningful).

struct CodecSpecificInfo;

// Each member represents an override of the VPX configuration if the optional
// value is set.
struct Vp8EncoderConfig {
 struct TemporalLayerConfig {
   bool operator!=(const TemporalLayerConfig& other) const {
     return ts_number_layers != other.ts_number_layers ||
            ts_target_bitrate != other.ts_target_bitrate ||
            ts_rate_decimator != other.ts_rate_decimator ||
            ts_periodicity != other.ts_periodicity ||
            ts_layer_id != other.ts_layer_id;
   }

   static constexpr size_t kMaxPeriodicity = 16;
   static constexpr size_t kMaxLayers = 5;

   // Number of active temporal layers. Set to 0 if not used.
   uint32_t ts_number_layers;

   // Arrays of length `ts_number_layers`, indicating (cumulative) target
   // bitrate and rate decimator (e.g. 4 if every 4th frame is in the given
   // layer) for each active temporal layer, starting with temporal id 0.
   std::array<uint32_t, kMaxLayers> ts_target_bitrate;
   std::array<uint32_t, kMaxLayers> ts_rate_decimator;

   // The periodicity of the temporal pattern. Set to 0 if not used.
   uint32_t ts_periodicity;

   // Array of length `ts_periodicity` indicating the sequence of temporal id's
   // to assign to incoming frames.
   std::array<uint32_t, kMaxPeriodicity> ts_layer_id;
 };

 std::optional<TemporalLayerConfig> temporal_layer_config;

 // Target bitrate, in bps.
 std::optional<uint32_t> rc_target_bitrate;

 // Clamp QP to max. Use 0 to disable clamping.
 std::optional<uint32_t> rc_max_quantizer;

 // Error resilience mode.
 std::optional<uint32_t> g_error_resilient;

 // If set to true, all previous configuration overrides should be reset.
 bool reset_previous_configuration_overrides = false;
};

// This interface defines a way of delegating the logic of buffer management.
// Multiple streams may be controlled by a single controller, demuxing between
// them using stream_index.
class Vp8FrameBufferController {
public:
 virtual ~Vp8FrameBufferController() = default;

 // Set limits on QP.
 // The limits are suggestion-only; the controller is allowed to exceed them.
 virtual void SetQpLimits(size_t stream_index, int min_qp, int max_qp) = 0;

 // Number of streamed controlled by `this`.
 virtual size_t StreamCount() const = 0;

 // If this method returns true, the encoder is free to drop frames for
 // instance in an effort to uphold encoding bitrate.
 // If this return false, the encoder must not drop any frames unless:
 //  1. Requested to do so via Vp8FrameConfig.drop_frame
 //  2. The frame to be encoded is requested to be a keyframe
 //  3. The encoder detected a large overshoot and decided to drop and then
 //     re-encode the image at a low bitrate. In this case the encoder should
 //     call OnFrameDropped() once to indicate drop, and then call
 //     OnEncodeDone() again when the frame has actually been encoded.
 virtual bool SupportsEncoderFrameDropping(size_t stream_index) const = 0;

 // New target bitrate for a stream (each entry in
 // `bitrates_bps` is for another temporal layer).
 virtual void OnRatesUpdated(size_t stream_index,
                             const std::vector<uint32_t>& bitrates_bps,
                             int framerate_fps) = 0;

 // Called by the encoder before encoding a frame. Returns a set of overrides
 // the controller wishes to enact in the encoder's configuration.
 // If a value is not overridden, previous overrides are still in effect.
 // However, if `Vp8EncoderConfig::reset_previous_configuration_overrides`
 // is set to `true`, all previous overrides are reset.
 virtual Vp8EncoderConfig UpdateConfiguration(size_t stream_index) = 0;

 // Returns the recommended VP8 encode flags needed.
 // The timestamp may be used as both a time and a unique identifier, and so
 // the caller must make sure no two frames use the same timestamp.
 // The timestamp uses a 90kHz RTP clock.
 // After calling this method, first call the actual encoder with the provided
 // frame configuration, and then OnEncodeDone() below.
 virtual Vp8FrameConfig NextFrameConfig(size_t stream_index,
                                        uint32_t rtp_timestamp) = 0;

 // Called after the encode step is done. `rtp_timestamp` must match the
 // parameter use in the NextFrameConfig() call.
 // `is_keyframe` must be true iff the encoder decided to encode this frame as
 // a keyframe.
 // If `info` is not null, the encoder may update `info` with codec specific
 // data such as temporal id. `qp` should indicate the frame-level QP this
 // frame was encoded at. If the encoder does not support extracting this, `qp`
 // should be set to 0.
 virtual void OnEncodeDone(size_t stream_index,
                           uint32_t rtp_timestamp,
                           size_t size_bytes,
                           bool is_keyframe,
                           int qp,
                           CodecSpecificInfo* info) = 0;

 // Called when a frame is dropped by the encoder.
 virtual void OnFrameDropped(size_t stream_index, uint32_t rtp_timestamp) = 0;

 // Called by the encoder when the packet loss rate changes.
 // `packet_loss_rate` runs between 0.0 (no loss) and 1.0 (everything lost).
 virtual void OnPacketLossRateUpdate(float packet_loss_rate) = 0;

 // Called by the encoder when the round trip time changes.
 virtual void OnRttUpdate(int64_t rtt_ms) = 0;

 // Called when a loss notification is received.
 virtual void OnLossNotification(
     const VideoEncoder::LossNotification& loss_notification) = 0;
};

// Interface for a factory of Vp8FrameBufferController instances.
class Vp8FrameBufferControllerFactory {
public:
 virtual ~Vp8FrameBufferControllerFactory() = default;

 // Clones oneself. (Avoids Vp8FrameBufferControllerFactoryFactory.)
 virtual std::unique_ptr<Vp8FrameBufferControllerFactory> Clone() const = 0;

 // Create a Vp8FrameBufferController instance.
 virtual std::unique_ptr<Vp8FrameBufferController> Create(
     const Environment& env,
     const VideoCodec& codec,
     const VideoEncoder::Settings& settings,
     FecControllerOverride* fec_controller_override) = 0;
};

}  // namespace webrtc

#endif  // API_VIDEO_CODECS_VP8_FRAME_BUFFER_CONTROLLER_H_