Opening the Scope
To use any of the video scopes just listed, open the video analyzer plug-in, select the required scope from the layout pull-down list or from the context menu. Open any video material for analyzing via the Cinegy Ingest plug-in and start its playback or recording. You can also analyze a frozen frame of a stopped video stream as a static image.
To visualize the color components using just one analyzer or some combination of analyzers, you can choose the layout configuration from the predefined set or define your custom configuration.
Scopes are designed for comprehensive video analysis of a defined video sequence. They make it possible to analyze the brightness, saturation, and a number of other parameters as well as display the results in the form of graphs. Each scope performs particular functions for analyzing video.
The video analyzing process provides real-time feedback during the playback of incoming video material, so the graphics that appear will be dynamic images. If the video stream is stopped or a static image is being displayed, the graph will be motionless as well.
Working with Waveform
The waveform scope displays the luma information of the incoming video stream in a form of a green traced wave. Luma is the brightness of an image without color information being taken into account.
The display of the luma level occurs relative to time. That is, if the frames being analyzed are dissimilar, the graph has a dynamic performance.
The conception of the graph construction is in the left-to-right scanning of each video frame and overlaying it in the waveform traces; i.e., the object on the left side of the frame (or image) corresponds to the left side of the waveform graph. Vertical tracing differs from the video frame representation. The brighter parts of the image are characterized by height of waves on the graph.
The graphic scale is located on the left of the waveform. The scale is marked in mV or in IRE depending on the video format of your video stream. Thus, the scale marks in mV for video in the PAL video format or in IRE for video in the NTSC video format.
The waveform graph is shown below:
The green vertical straight line that indicates waveform extreme points locations. It is located to the right of the graph.
One of the waveform analyzer tasks is to help detect the brightness safe color limits. To define the black level limit at 7.5 IRE for the NTSC video format, configure the corresponding settings in the Video analyzer settings dialog. A zero limit for the graph will be redefined to the 7.5 IRE level and will be displayed as a dotted line:
This setting does not affect the analyzed video, just the scale by which it is measured.
The waveform scope displays the components encoded as a composite video including the chroma signal. Chroma is derived from the blue (Cb) and red (Cr) chroma components, i.e. displayed in the form of a cyan (blue-green) wave over the top of the luma waveform.
Configure the YC waveform in the Video analyzer settings dialog to get the chroma waveform visualization as it is shown in the following image:
Working with Histogram
The histogram scope is the most convenient tool for analyzing frequency distributions. A frequency distribution shows how often each value in a set of data occurs.
The histogram scope provides pixel-by-pixel analysis of the incoming video signal for getting the information about the color values of each frame. The results obtained from the analysis are plotted on a graph, where the horizontal axis indicates the color values and vertical axis indicates the number of pixels contained in the current frame.
The histogram is displayed in two color models: the RGB model or the YCbCr model.
The RGB histogram graphically displays the distribution of points in RGB-space corresponding to the colors of the frame or image pixels. The graph appears in the form of a wave, i.e. formed by a number of peaks. Concentration of peaks from the left of the graph appears when the frame mainly consists of the darkest values of red, green and blue and, accordingly, the brightest values appear as peaks on the right.
The graph shows the color channel division where red, green and blue bars are represented one under another. The number of pixels containing red, green or blue value is indicated by the height of a peak. The number of similar values in the frame is indicated by the peak width.
The following illustration shows the example of a histogram in the RGB color model:
The YCrCb histogram displays the distribution of points in YCrCb-space according to pixels of an image. This graph, like RGB histogram, appears as a wave formed by a number of peaks and is divided into Y, Cb and Cr component bars.
The number of pixels in the current frame containing Y, Cb or Cr values is indicated with the height of a peak. The number of similar values in the frame is indicated with the peak width.
The peaks concentration from the left of the bar that represents Y values appears when the frame consists mainly of the darkest values and, accordingly, the brightest values appear as peaks located on the right.
The following illustration shows the example of a histogram in the YCbCr color model:
Working with Parade
The parade scope displays a graph, separated into three bars, that shows the information concerning the current video components in defined image of video sequence.
The left side of the waveform graph shows a scale divided into 10 points (from 0 to 100) that forms a background grid.
The parade scope is performed in two color models: RGB parade or YCbCr parade. The color model is specified in the Video analyzer settings dialog.
RGB parade displays red, green and blue components shown as correspondingly colored waveforms located side by side.
One of the parade scope functions is to help to detect camera problems by analyzing the captured RGB signal. RGB signals are able to be combined in various ways to reproduce other colors. RGB parade is used for red, green and blue colors separation.
A description of the frame or image coloring on the graph is as follows:
the black color is represented as level lines in each of red, green and blue waveforms located at zero;
the white color is displayed as level lines in all three waveforms located at the top. A high level of one of the three primary colors displayed does not mean the same coloring of the incoming video, until the levels of the rest of the color components become low.
The following illustration shows an example of an RGB parade:
YCbCr parade displays waveforms of Y, Cb and Cr components located side by side. The Y waveform coloring is blue, Cb is cyan, and Cr is yellow.
The Y component represents the waveform with luma information. It is located on the left side of a graph.
Cb and Cr components are located in the center and from the right side on the graph accordingly. They are different color signals and display the color information without consideration for the luma information. Cb and Cr components are represented as level lines located halfway up on the graph for black or white images. Different color signals relocate from the bisecting point of a graph when the frame or image gains a color cast.
The following illustration shows an example of a YCbCr parade:
Working with Vectorscope
The vectorscope measures chromatic video data including the hue and saturation information; it also keeps track of the color range offsets. It displays information about just the chroma (coloring) portion of the video signal as a circular graph where the center represents no chroma. Increasing of the chroma signal causes the trace to grow and move away from the center.
Each color in the frame or image is displayed as a spot on the vectorscope graph. The displacement from the centre towards the color spot indicates the chroma saturation level. The hue level is indicated with an angle, formed by a pintle and by a line connecting the color spot with the origin.
The appearance of a spot at the center of the figure indicates the presence of black, white or gray colored areas in the current frame or image. More saturated areas appear further out from the center.
The vectorscope figure may be displayed in two saturation coefficients: 75% or 100%. When the mode with 75% is selected, it is displayed with six square targets, located all around the vectorscope graph. These targets indicate the hit of chroma vector termination for each color bar.
The following illustration shows an example of the vectorscope in 75% saturation mode:
When the mode with 100% saturation is selected, the second target is available for display. The second target provides six additional targets that represent hits of chroma vectors termination for 75% saturation.
The following illustration shows an example of the vectorscope in 100% saturation mode with a set of second targets displayed:
The targets positions move depending on the video mode (HD or SD video) specification of the incoming video signal.
|Use the Video analyzer settings dialog to define the display mode of 75% or 100% saturation.|
The "I" and "Q" axes are provided for the NTSC signal analysis in YIQ color space.