media/capture/video/file_video_capture_device.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_VIDEO_CAPTURE_FILE_VIDEO_CAPTURE_DEVICE_H_
   6 #define MEDIA_VIDEO_CAPTURE_FILE_VIDEO_CAPTURE_DEVICE_H_
   7
   8 #include <string>
   9
  10 #include "base/files/file.h"
  11 #include "base/files/memory_mapped_file.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/threading/thread.h"
  14 #include "base/threading/thread_checker.h"
  15 #include "media/capture/video/video_capture_device.h"
  16
  17 namespace media {
  18
  19 class VideoFileParser;
  20
  21 // Implementation of a VideoCaptureDevice class that reads from a file. Used for
  22 // testing the video capture pipeline when no real hardware is available. The
  23 // supported file formats are YUV4MPEG2 (a.k.a. Y4M) and MJPEG/JPEG. YUV4MPEG2
  24 // is a minimal container with a series of uncompressed video only frames, see
  25 // the link http://wiki.multimedia.cx/index.php?title=YUV4MPEG2 for more
  26 // information on the file format. Several restrictions and notes apply, see the
  27 // implementation file.
  28 // Example Y4M videos can be found in http://media.xiph.org/video/derf.
  29 // Example MJPEG videos can be found in media/data/test/bear.mjpeg.
  30 // Restrictions: Y4M videos should have .y4m file extension and MJPEG videos
  31 // should have .mjpeg file extension.
  32 class MEDIA_EXPORT FileVideoCaptureDevice : public VideoCaptureDevice {
  33  public:
  34   // Reads and parses the header of a |file_path|, returning the collected
  35   // pixel format in |video_format|. Returns true on file parsed successfully,
  36   // or false.
  37   // Restrictions: Only trivial Y4M per-frame headers and MJPEG are supported.
  38   static bool GetVideoCaptureFormat(const base::FilePath& file_path,
  39                                     media::VideoCaptureFormat* video_format);
  40
  41   // Constructor of the class, with a fully qualified file path as input, which
  42   // represents the Y4M or MJPEG file to stream repeatedly.
  43   explicit FileVideoCaptureDevice(const base::FilePath& file_path);
  44
  45   // VideoCaptureDevice implementation, class methods.
  46   ~FileVideoCaptureDevice() override;
  47   void AllocateAndStart(const VideoCaptureParams& params,
  48                         scoped_ptr<VideoCaptureDevice::Client> client) override;
  49   void StopAndDeAllocate() override;
  50
  51  private:
  52   // Opens a given file |file_path| for reading, and stores collected format
  53   // information in |video_format|. Returns the parsed file to the
  54   // caller, who is responsible for closing it.
  55   static scoped_ptr<VideoFileParser> GetVideoFileParser(
  56       const base::FilePath& file_path,
  57       media::VideoCaptureFormat* video_format);
  58
  59   // Called on the |capture_thread_|.
  60   void OnAllocateAndStart(const VideoCaptureParams& params,
  61                           scoped_ptr<Client> client);
  62   void OnStopAndDeAllocate();
  63   const uint8_t* GetNextFrame();
  64   void OnCaptureTask();
  65
  66   // |thread_checker_| is used to check that destructor, AllocateAndStart() and
  67   // StopAndDeAllocate() are called in the correct thread that owns the object.
  68   base::ThreadChecker thread_checker_;
  69
  70   // |capture_thread_| is used for internal operations via posting tasks to it.
  71   // It is active between OnAllocateAndStart() and OnStopAndDeAllocate().
  72   base::Thread capture_thread_;
  73   // The following members belong to |capture_thread_|.
  74   scoped_ptr<VideoCaptureDevice::Client> client_;
  75   const base::FilePath file_path_;
  76   scoped_ptr<VideoFileParser> file_parser_;
  77   VideoCaptureFormat capture_format_;
  78   // Target time for the next frame.
  79   base::TimeTicks next_frame_time_;
  80
  81   DISALLOW_COPY_AND_ASSIGN(FileVideoCaptureDevice);
  82 };
  83
  84 }  // namespace media
  85
  86 #endif  // MEDIA_VIDEO_CAPTURE_FILE_VIDEO_CAPTURE_DEVICE_H_