FFmpeg: Combine 2 constructors via a default arg, fix docs, const refs

include/FFmpegReader.h

@@ -233,14 +233,13 @@ namespace openshot {
 		/// codecs have trouble seeking, and can introduce artifacts or blank images into the video.
 		bool enable_seek;
 
-		/// Constructor for FFmpegReader.  This automatically opens the media file and loads
-		/// frame 1, or it throws one of the following exceptions.
-		FFmpegReader(std::string path);
-
-		/// Constructor for FFmpegReader.  This only opens the media file to inspect its properties
-		/// if inspect_reader=true. When not inspecting the media file, it's much faster, and useful
-		/// when you are inflating the object using JSON after instantiating it.
-		FFmpegReader(std::string path, bool inspect_reader);
+		/// @brief Constructor for FFmpegReader.
+		///
+		/// Sets (and possibly opens) the media file path,
+		/// or throws an exception.
+		/// @param path  The filesystem location to load
+		/// @param inspect_reader  if true (the default), automatically open the media file and loads frame 1.
+		FFmpegReader(const std::string& path, bool inspect_reader=true);
 
 		/// Destructor
 		virtual ~FFmpegReader();

include/FFmpegWriter.h

@@ -251,9 +251,11 @@ namespace openshot {
 
 	public:
 
-		/// @brief Constructor for FFmpegWriter. Throws one of the following exceptions.
+		/// @brief Constructor for FFmpegWriter.
+		/// Throws an exception on failure to open path.
+		///
 		/// @param path The file path of the video file you want to open and read
-		FFmpegWriter(std::string path);
+		FFmpegWriter(const std::string& path);
 
 		/// Close the writer
 		void Close();

src/FFmpegReader.cpp

@@ -83,35 +83,14 @@ int hw_de_on = 0;
 	AVHWDeviceType hw_de_av_device_type_global = AV_HWDEVICE_TYPE_NONE;
 #endif
 
-FFmpegReader::FFmpegReader(std::string path)
+FFmpegReader::FFmpegReader(const std::string& path, bool inspect_reader)
 		: last_frame(0), is_seeking(0), seeking_pts(0), seeking_frame(0), seek_count(0),
 		  audio_pts_offset(99999), video_pts_offset(99999), path(path), is_video_seek(true), check_interlace(false),
 		  check_fps(false), enable_seek(true), is_open(false), seek_audio_frame_found(0), seek_video_frame_found(0),
 		  prev_samples(0), prev_pts(0), pts_total(0), pts_counter(0), is_duration_known(false), largest_frame_processed(0),
 		  current_video_frame(0), has_missing_frames(false), num_packets_since_video_frame(0), num_checks_since_final(0),
 		  packet(NULL) {
 
-	// Initialize FFMpeg, and register all formats and codecs
-	AV_REGISTER_ALL
-	AVCODEC_REGISTER_ALL
-
-	// Init cache
-	working_cache.SetMaxBytesFromInfo(OPEN_MP_NUM_PROCESSORS * info.fps.ToDouble() * 2, info.width, info.height, info.sample_rate, info.channels);
-	missing_frames.SetMaxBytesFromInfo(OPEN_MP_NUM_PROCESSORS * 2, info.width, info.height, info.sample_rate, info.channels);
-	final_cache.SetMaxBytesFromInfo(OPEN_MP_NUM_PROCESSORS * 2, info.width, info.height, info.sample_rate, info.channels);
-
-	// Open and Close the reader, to populate its attributes (such as height, width, etc...)
-	Open();
-	Close();
-}
-
-FFmpegReader::FFmpegReader(std::string path, bool inspect_reader)
-		: last_frame(0), is_seeking(0), seeking_pts(0), seeking_frame(0), seek_count(0),
-		  audio_pts_offset(99999), video_pts_offset(99999), path(path), is_video_seek(true), check_interlace(false),
-		  check_fps(false), enable_seek(true), is_open(false), seek_audio_frame_found(0), seek_video_frame_found(0),
-		  prev_samples(0), prev_pts(0), pts_total(0), pts_counter(0), is_duration_known(false), largest_frame_processed(0),
-		  current_video_frame(0), has_missing_frames(false), num_packets_since_video_frame(0), num_checks_since_final(0),
-		  packet(NULL) {
 
 	// Initialize FFMpeg, and register all formats and codecs
 	AV_REGISTER_ALL

src/FFmpegWriter.cpp

@@ -83,7 +83,7 @@ static int set_hwframe_ctx(AVCodecContext *ctx, AVBufferRef *hw_device_ctx, int6
 }
 #endif // HAVE_HW_ACCEL
 
-FFmpegWriter::FFmpegWriter(std::string path) :
+FFmpegWriter::FFmpegWriter(const std::string& path) :
 		path(path), fmt(NULL), oc(NULL), audio_st(NULL), video_st(NULL), samples(NULL),
 		audio_outbuf(NULL), audio_outbuf_size(0), audio_input_frame_size(0), audio_input_position(0),
 		initial_audio_input_frame_size(0), img_convert_ctx(NULL), cache_size(8), num_of_rescalers(32),