| // Copyright 2015 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef MEDIA_CAPTURE_VIDEO_CAPTURER_SOURCE_H_ |
| #define MEDIA_CAPTURE_VIDEO_CAPTURER_SOURCE_H_ |
| |
| #include <string> |
| #include <vector> |
| |
| #include "base/callback.h" |
| #include "base/memory/ref_counted.h" |
| #include "base/time/time.h" |
| #include "media/capture/capture_export.h" |
| #include "media/capture/video_capture_types.h" |
| |
| namespace media { |
| |
| class VideoFrame; |
| |
| // VideoCapturerSource is an interface representing the source for captured |
| // video. An implementation will periodically call the frame callback with new |
| // video frames. |
| class CAPTURE_EXPORT VideoCapturerSource { |
| public: |
| virtual ~VideoCapturerSource(); |
| |
| // This callback is used to deliver video frames. |
| // |
| // |estimated_capture_time| - The capture time of the delivered video |
| // frame. This field represents the local time at which either: 1) the frame |
| // was generated, if it was done so locally; or 2) the targeted play-out time |
| // of the frame, if it was generated from a remote source. Either way, an |
| // implementation should not present the frame before this point-in-time. This |
| // value is NOT a high-resolution timestamp, and so it should not be used as a |
| // presentation time; but, instead, it should be used for buffering playback |
| // and for A/V synchronization purposes. NOTE: It is possible for this value |
| // to be null if the current implementation lacks this timing information. |
| // |
| // |video_frame->timestamp()| gives the presentation timestamp of the video |
| // frame relative to the first frame generated by the corresponding source. |
| // Because a source can start generating frames before a subscriber is added, |
| // the first video frame delivered may not have timestamp equal to 0. |
| using VideoCaptureDeliverFrameCB = |
| base::Callback<void(const scoped_refptr<media::VideoFrame>& video_frame, |
| base::TimeTicks estimated_capture_time)>; |
| |
| using VideoCaptureDeviceFormatsCB = |
| base::Callback<void(const media::VideoCaptureFormats&)>; |
| |
| using RunningCallback = base::Callback<void(bool)>; |
| |
| // Returns formats that are preferred and can currently be used. May be empty |
| // if no formats are available or known. |
| virtual VideoCaptureFormats GetPreferredFormats() = 0; |
| |
| // Starts capturing frames using the capture |params|. |new_frame_callback| is |
| // triggered when a new video frame is available. |
| // If capturing is started successfully then |running_callback| will be |
| // called with a parameter of true. Note that some implementations may |
| // simply reject StartCapture (by calling running_callback with a false |
| // argument) if called with the wrong task runner. |
| // If capturing fails to start or stopped due to an external event then |
| // |running_callback| will be called with a parameter of false. |
| // |running_callback| will always be called on the same thread as the |
| // StartCapture. |
| virtual void StartCapture( |
| const media::VideoCaptureParams& params, |
| const VideoCaptureDeliverFrameCB& new_frame_callback, |
| const RunningCallback& running_callback) = 0; |
| |
| // Asks source to send a refresh frame. In cases where source does not provide |
| // a continuous rate of new frames (e.g. canvas capture, screen capture where |
| // the screen's content has not changed in a while), consumers may request a |
| // "refresh frame" to be delivered. For instance, this would be needed when |
| // a new sink is added to a MediaStreamTrack. |
| // |
| // The default implementation is a no-op and implementations are not required |
| // to honor this request. If they decide to and capturing is started |
| // successfully, then |new_frame_callback| should be called with a frame. |
| // |
| // Note: This should only be called after StartCapture() and before |
| // StopCapture(). Otherwise, its behavior is undefined. |
| virtual void RequestRefreshFrame() {} |
| |
| // Optionally suspends frame delivery. The source may or may not honor this |
| // request. Thus, the caller cannot assume frame delivery will actually |
| // stop. Even if frame delivery is suspended, this might not take effect |
| // immediately. |
| // |
| // The purpose of this is to allow minimizing resource usage while |
| // there are no frame consumers present. |
| // |
| // Note: This should only be called after StartCapture() and before |
| // StopCapture(). Otherwise, its behavior is undefined. |
| virtual void MaybeSuspend() {} |
| |
| // Resumes frame delivery, if it was suspended. If frame delivery was not |
| // suspended, this is a no-op, and frame delivery will continue. |
| // |
| // Note: This should only be called after StartCapture() and before |
| // StopCapture(). Otherwise, its behavior is undefined. |
| virtual void Resume() {} |
| |
| // Stops capturing frames and clears all callbacks including the |
| // SupportedFormatsCallback callback. Note that queued frame callbacks |
| // may still occur after this call, so the caller must take care to |
| // use refcounted or weak references in |new_frame_callback|. |
| virtual void StopCapture() = 0; |
| }; |
| |
| } // namespace media |
| |
| #endif // MEDIA_CAPTURE_VIDEO_CAPTURER_SOURCE_H_ |