video_source_interface.h

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/*

 *  Copyright (c) 2016 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_VIDEO_SOURCE_INTERFACE_H_

#define API_VIDEO_VIDEO_SOURCE_INTERFACE_H_

#include <limits>

#include <optional>

#include <vector>

#include "api/video/video_sink_interface.h"

#include "rtc_base/system/rtc_export.h"

namespace rtc {

// VideoSinkWants is used for notifying the source of properties a video frame

// should have when it is delivered to a certain sink.

struct RTC_EXPORT VideoSinkWants {

  struct FrameSize {

    FrameSize(int width, int height) : width(width), height(height) {}

    FrameSize(const FrameSize&) = default;

    ~FrameSize() = default;

    int width;

    int height;

};

  VideoSinkWants();

  VideoSinkWants(const VideoSinkWants&);

  ~VideoSinkWants();

  // Tells the source whether the sink wants frames with rotation applied.

  // By default, any rotation must be applied by the sink.

  bool rotation_applied = false;

  // Tells the source that the sink only wants black frames.

  bool black_frames = false;

  // Tells the source the maximum number of pixels the sink wants.

  int max_pixel_count = std::numeric_limits<int>::max();

  // Tells the source the desired number of pixels the sinks wants. This will

  // typically be used when stepping the resolution up again when conditions

  // have improved after an earlier downgrade. The source should select the

  // closest resolution to this pixel count, but if max_pixel_count is set, it

  // still sets the absolute upper bound.

  std::optional<int> target_pixel_count;

  // Tells the source the maximum framerate the sink wants.

  int max_framerate_fps = std::numeric_limits<int>::max();

  // Tells the source that the sink wants width and height of the video frames

  // to be divisible by `resolution_alignment`.

  // For example: With I420, this value would be a multiple of 2.

  // Note that this field is unrelated to any horizontal or vertical stride

  // requirements the encoder has on the incoming video frame buffers.

  int resolution_alignment = 1;

  // The resolutions that sink is configured to consume. If the sink is an

  // encoder this is what the encoder is configured to encode. In singlecast we

  // only encode one resolution, but in simulcast and SVC this can mean multiple

  // resolutions per frame.

//

  // The sink is always configured to consume a subset of the

  // webrtc::VideoFrame's resolution. In the case of encoding, we usually encode

  // at webrtc::VideoFrame's resolution but this may not always be the case due

  // to scaleResolutionDownBy or turning off simulcast or SVC layers.

//

  // For example, we may capture at 720p and due to adaptation (e.g. applying

  // `max_pixel_count` constraints) create webrtc::VideoFrames of size 480p, but

  // if we do scaleResolutionDownBy:2 then the only resolution we end up

  // encoding is 240p. In this case we still need to provide webrtc::VideoFrames

  // of size 480p but we can optimize internal buffers for 240p, avoiding

  // downsampling to 480p if possible.

//

  // Note that the `resolutions` can change while frames are in flight and

  // should only be used as a hint when constructing the webrtc::VideoFrame.

  std::vector<FrameSize> resolutions;

  // This is the resolution requested by the user using RtpEncodingParameters.

  std::optional<FrameSize> requested_resolution;

  // `is_active` : Is this VideoSinkWants from an encoder that is encoding any

  // layer. IF YES, it will affect how the VideoAdapter will choose to

  // prioritize the OnOutputFormatRequest vs. requested_resolution. IF NO,

  // VideoAdapter consider this VideoSinkWants as a passive listener (e.g a

  // VideoRenderer or a VideoEncoder that is not currently actively encoding).

  bool is_active = false;

  // This sub-struct contains information computed by VideoBroadcaster

  // that aggregates several VideoSinkWants (and sends them to

  // AdaptedVideoTrackSource).

  struct Aggregates {

    // `active_without_requested_resolution` is set by VideoBroadcaster

    // when aggregating sink wants if there exists any sink (encoder) that is

    // active but has not set the `requested_resolution`, i.e is relying on

    // OnOutputFormatRequest to handle encode resolution.

    bool any_active_without_requested_resolution = false;

};

  std::optional<Aggregates> aggregates;

};

inline bool operator==(const VideoSinkWants::FrameSize& a,

                       const VideoSinkWants::FrameSize& b) {

  return a.width == b.width && a.height == b.height;

inline bool operator!=(const VideoSinkWants::FrameSize& a,

                       const VideoSinkWants::FrameSize& b) {

  return !(a == b);

template <typename VideoFrameT>

class VideoSourceInterface {

 public:

  virtual ~VideoSourceInterface() = default;

  virtual void AddOrUpdateSink(VideoSinkInterface<VideoFrameT>* sink,

                               const VideoSinkWants& wants) = 0;

  // RemoveSink must guarantee that at the time the method returns,

  // there is no current and no future calls to VideoSinkInterface::OnFrame.

  virtual void RemoveSink(VideoSinkInterface<VideoFrameT>* sink) = 0;

  // Request underlying source to capture a new frame.

  // TODO(crbug/1255737): make pure virtual once downstream projects adapt.

  virtual void RequestRefreshFrame() {}

};

}  // namespace rtc

#endif  // API_VIDEO_VIDEO_SOURCE_INTERFACE_H_