grammar corrections for python gui docs

doc/py_tutorials/py_gui/py_table_of_contents_gui.markdown

@@ -4,21 +4,21 @@ Gui Features in OpenCV {#tutorial_py_table_of_contents_gui}
 -   @subpage tutorial_py_image_display
 
     Learn to load an
-    image, display it and save it back
+    image, display it, and save it back
 
 -   @subpage tutorial_py_video_display
 
     Learn to play videos,
-    capture videos from Camera and write it as a video
+    capture videos from a camera, and write videos
 
 -   @subpage tutorial_py_drawing_functions
 
     Learn to draw lines,
-    rectangles, ellipses, circles etc with OpenCV
+    rectangles, ellipses, circles, etc with OpenCV
 
 -   @subpage tutorial_py_mouse_handling
 
-    Draw stuffs with your
+    Draw stuff with your
     mouse
 
 -   @subpage tutorial_py_trackbar

doc/py_tutorials/py_gui/py_video_display/py_video_display.markdown

@@ -4,19 +4,19 @@ Getting Started with Videos {#tutorial_py_video_display}
 Goal
 ----
 
--   Learn to read video, display video and save video.
--   Learn to capture from Camera and display it.
+-   Learn to read video, display video, and save video.
+-   Learn to capture video from a camera and display it.
 -   You will learn these functions : **cv.VideoCapture()**, **cv.VideoWriter()**
 
 Capture Video from Camera
 -------------------------
 
-Often, we have to capture live stream with camera. OpenCV provides a very simple interface to this.
-Let's capture a video from the camera (I am using the in-built webcam of my laptop), convert it into
+Often, we have to capture live stream with a camera. OpenCV provides a very simple interface to do this.
+Let's capture a video from the camera (I am using the built-in webcam on my laptop), convert it into
 grayscale video and display it. Just a simple task to get started.
 
 To capture a video, you need to create a **VideoCapture** object. Its argument can be either the
-device index or the name of a video file. Device index is just the number to specify which camera.
+device index or the name of a video file. A device index is just the number to specify which camera.
 Normally one camera will be connected (as in my case). So I simply pass 0 (or -1). You can select
 the second camera by passing 1 and so on. After that, you can capture frame-by-frame. But at the
 end, don't forget to release the capture.
@@ -46,16 +46,16 @@ while True:
 # When everything done, release the capture
 cap.release()
 cv.destroyAllWindows()@endcode
-`cap.read()` returns a bool (`True`/`False`). If frame is read correctly, it will be `True`. So you can
-check end of the video by checking this return value.
+`cap.read()` returns a bool (`True`/`False`). If the frame is read correctly, it will be `True`. So you can
+check for the end of the video by checking this returned value.
 
-Sometimes, cap may not have initialized the capture. In that case, this code shows error. You can
+Sometimes, cap may not have initialized the capture. In that case, this code shows an error. You can
 check whether it is initialized or not by the method **cap.isOpened()**. If it is `True`, OK.
 Otherwise open it using **cap.open()**.
 
 You can also access some of the features of this video using **cap.get(propId)** method where propId
 is a number from 0 to 18. Each number denotes a property of the video (if it is applicable to that
-video) and full details can be seen here: cv::VideoCapture::get().
+video). Full details can be seen here: cv::VideoCapture::get().
 Some of these values can be modified using **cap.set(propId, value)**. Value is the new value you
 want.
 
@@ -63,13 +63,13 @@ For example, I can check the frame width and height by `cap.get(cv.CAP_PROP_FRAM
 640x480 by default. But I want to modify it to 320x240. Just use `ret = cap.set(cv.CAP_PROP_FRAME_WIDTH,320)` and
 `ret = cap.set(cv.CAP_PROP_FRAME_HEIGHT,240)`.
 
-@note If you are getting error, make sure camera is working fine using any other camera application
+@note If you are getting an error, make sure your camera is working fine using any other camera application
 (like Cheese in Linux).
 
 Playing Video from file
 -----------------------
 
-It is same as capturing from Camera, just change camera index with video file name. Also while
+Playing video from file is the same as capturing it from camera, just change the camera index to a video file name. Also while
 displaying the frame, use appropriate time for `cv.waitKey()`. If it is too less, video will be very
 fast and if it is too high, video will be slow (Well, that is how you can display videos in slow
 motion). 25 milliseconds will be OK in normal cases.
@@ -96,23 +96,23 @@ cap.release()
 cv.destroyAllWindows()
 @endcode
 
-@note Make sure proper versions of ffmpeg or gstreamer is installed. Sometimes, it is a headache to
-work with Video Capture mostly due to wrong installation of ffmpeg/gstreamer.
+@note Make sure a proper version of ffmpeg or gstreamer is installed. Sometimes it is a headache to
+work with video capture, mostly due to wrong installation of ffmpeg/gstreamer.
 
 Saving a Video
 --------------
 
-So we capture a video, process it frame-by-frame and we want to save that video. For images, it is
-very simple, just use `cv.imwrite()`. Here a little more work is required.
+So we capture a video and process it frame-by-frame, and we want to save that video. For images, it is
+very simple: just use `cv.imwrite()`. Here, a little more work is required.
 
 This time we create a **VideoWriter** object. We should specify the output file name (eg:
 output.avi). Then we should specify the **FourCC** code (details in next paragraph). Then number of
-frames per second (fps) and frame size should be passed. And last one is **isColor** flag. If it is
-`True`, encoder expect color frame, otherwise it works with grayscale frame.
+frames per second (fps) and frame size should be passed. And the last one is the **isColor** flag. If it is
+`True`, the encoder expect color frame, otherwise it works with grayscale frame.
 
 [FourCC](http://en.wikipedia.org/wiki/FourCC) is a 4-byte code used to specify the video codec. The
 list of available codes can be found in [fourcc.org](http://www.fourcc.org/codecs.php). It is
-platform dependent. Following codecs works fine for me.
+platform dependent. The following codecs work fine for me.
 
 -   In Fedora: DIVX, XVID, MJPG, X264, WMV1, WMV2. (XVID is more preferable. MJPG results in high
     size video. X264 gives very small size video)
@@ -122,7 +122,7 @@ platform dependent. Following codecs works fine for me.
 FourCC code is passed as `cv.VideoWriter_fourcc('M','J','P','G')` or
 `cv.VideoWriter_fourcc(*'MJPG')` for MJPG.
 
-Below code capture from a Camera, flip every frame in vertical direction and saves it.
+The below code captures from a camera, flips every frame in the vertical direction, and saves the video.
 @code{.py}
 import numpy as np
 import cv2 as cv