videoio: Add raw encoded video stream encapsulation to cv::VideoWriter with CAP_FFMPEG

modules/videoio/include/opencv2/videoio.hpp

@@ -225,10 +225,13 @@ enum VideoWriterProperties {
   VIDEOWRITER_PROP_NSTRIPES = 3,   //!< Number of stripes for parallel encoding. -1 for auto detection.
   VIDEOWRITER_PROP_IS_COLOR = 4,   //!< If it is not zero, the encoder will expect and encode color frames, otherwise it
                                    //!< will work with grayscale frames.
-  VIDEOWRITER_PROP_DEPTH = 5,      //!< Defaults to CV_8U.
+  VIDEOWRITER_PROP_DEPTH = 5,      //!< Defaults to \ref CV_8U.
   VIDEOWRITER_PROP_HW_ACCELERATION = 6, //!< (**open-only**) Hardware acceleration type (see #VideoAccelerationType). Setting supported only via `params` parameter in VideoWriter constructor / .open() method. Default value is backend-specific.
   VIDEOWRITER_PROP_HW_DEVICE       = 7, //!< (**open-only**) Hardware device index (select GPU if multiple available). Device enumeration is acceleration type specific.
   VIDEOWRITER_PROP_HW_ACCELERATION_USE_OPENCL= 8, //!< (**open-only**) If non-zero, create new OpenCL context and bind it to current thread. The OpenCL context created with Video Acceleration context attached it (if not attached yet) for optimized GPU data copy between cv::UMat and HW accelerated encoder.
+  VIDEOWRITER_PROP_RAW_VIDEO = 9, //!< (**open-only**) Set to non-zero to enable encapsulation of an encoded raw video stream. Each raw encoded video frame should be passed to VideoWriter::write() as single row or column of a \ref CV_8UC1 Mat. \note If the key frame interval is not 1 then it must be manually specified by the user. This can either be performed during initialization passing \ref VIDEOWRITER_PROP_KEY_INTERVAL as one of the extra encoder params  to \ref VideoWriter::VideoWriter(const String &, int, double, const Size &, const std::vector< int > &params) or afterwards by setting the \ref VIDEOWRITER_PROP_KEY_FLAG with \ref VideoWriter::set() before writing each frame. FFMpeg backend only.
+  VIDEOWRITER_PROP_KEY_INTERVAL = 10, //!< (**open-only**) Set the key frame interval using raw video encapsulation (\ref VIDEOWRITER_PROP_RAW_VIDEO != 0). Defaults to 1 when not set. FFMpeg backend only.
+  VIDEOWRITER_PROP_KEY_FLAG = 11, //!< Set to non-zero to signal that the following frames are key frames or zero if not, when encapsulating raw video (\ref VIDEOWRITER_PROP_RAW_VIDEO != 0). FFMpeg backend only.
 #ifndef CV_DOXYGEN
   CV__VIDEOWRITER_PROP_LATEST
 #endif

modules/videoio/src/cap_ffmpeg.cpp

@@ -198,7 +198,11 @@ class CvVideoWriter_FFMPEG_proxy CV_FINAL :
         return ffmpegWriter->getProperty(propId);
     }
 
-    virtual bool setProperty(int, double) CV_OVERRIDE { return false; }
+    virtual bool setProperty(int propId, double value) CV_OVERRIDE {
+        if (!ffmpegWriter)
+            return 0;
+        return ffmpegWriter->setProperty(propId, value);
+    }
     virtual bool isOpened() const CV_OVERRIDE { return ffmpegWriter != 0; }
 
 protected: