VQ Probe v1.5 User Guide
- Offline Activation
- Graphical User Interface Overview
- Video Quality Metrics
- Known Limitations
- Third Party Libraries
VQ Probe is a software tool for Video Elementary Stream visual comparison.
The tool is shipped as a Graphical User Interface application for Windows, macOS, and Linux.
Supported Video Codecs
- H.266/VVC VTM-10.0 (4:2:0 only)
Supported Uncompressed Formats
Supported Chroma Subsampling
Supported Bit Depth
- 8 bit
- 10 bit
Supported Video Metrics
- PSNR: calculated based on the regular formula (Peak signal-to-noise ratio); average noise of every pixel of the whole frame is calculated
- SSIM: we compute SSIM using the empirical downsampling process. For each image let F = max(1, round(N/256)), where N is the height of an image in pixels. The image is averaged within an F by F window and downsampled by a factor of F. Then the SSIM index is calculated by the following formula:
- C1 and C2 are constants equal to (k1L)2 and (k2L)2, respectively, where by default k1 = 0.01, k2 = 0.03, and L is the dynamic range of the images;
- μ1 and μ2 are the compared windows;
- σ1 is the difference between the first image squared and (μ1)2;
- σ2 is the difference between the second image squared and (μ2)2;
- σ12 is the difference between the multiplication of the images and μ1μ2.
- VMAF: the algorithm and the model v0.6.1 (https://github.com/Netflix/vmaf) are used for VMAF calculation. Please follow VMAF: The Journey Continues for more information.
VQ Probe requires your computer to be connected to the Internet to start your trial period. If you have no Internet connection or have restricted Internet access, then you have the option of activating your copy of VQ Probe offline. To do so:
- Go to Help > Offline Activation.... A dialog will be opened:
- Press the Next button. The next page will appear:
- Offline Activation is already chosen. Just press the Next button again. An instruction will appear:
- Log in to https://portal.vicuesoft.com with the email you used to download VQ Probe.
- Go to the Licenses page: https://portal.vicuesoft.com/private/licenses
- Press Generate Key next to your VQ Probe license:
- A key will be generated:
- Copy it. Return to VQ Probe application's Offline Activation Dialog and paste it:
- Press the Generate Request File button and choose the location where the generated file should be saved.
- Once the Save button is pressed, the file will be generated. In case of success, the green message will appear under the button, and you can go to the wizard's next page: Otherwise, the red error message will appear: Please fix the issue and try to generate the file again.
- Return back to the Customer Portal and click the Offline Activation button:
- Next, you will see the page of VQ Probe offline activation. Press the Choose File button:
- In the opened dialog choose the file you have created in step 10. Then press the Upload button.
- A Response File will be downloaded automatically to your default downloads folder.
- Go to VQ Probe, press Upload Response File and choose the file you have just received:
- In case of no errors you will see the green message: Congratulations! Your copy of VQ Probe is activated. In case of the red error message please check your key, make sure you have chosen the correct files, and then try again.
NOTE: In case of any difficulties please contact us at email@example.com
Graphical User Interface Overview
The main window of VQ Probe has the following elements:
- Project View
- Playback View
- Quality Metrics View
The window used to set up and manage your workspace: add and remove video files, select which ones will be displayed in Playback View, create and remove RD Curves, set the RD Curve anchor used for BD Rate calculation.
The view can be shown or hidden by using Window > Project View from the main menu, or by using hotkeys (Ctrl + Shift + P on Windows and Linux, or Cmd + Shift + P on macOS).
- Left file area displays a part of the current frame of the left file
- Right file area displays a part of the current frame of the right file
- Vertical split line is placed between two images; it allows the user to change the width of the left and right images
- Buttons to choose which component(s) are shown:
- YUV: show YUV
- Y: show only Y plane
- U: show only U plane
- V: show only V plane
- Buttons to choose the format of numbers in Playback View
- dec: show numbers as decimal
- hex: show numbers as hexadecimal
- View mode:
- L|R: show the left and the right files divided by the splitter line
- Ref: show the reference file
- L|R / Ref Diff: show the difference between the left and the reference files on the left side of the screen and the difference between the right and the reference files on the right side of the screen
- B/W Diff: show the difference just like L|R / Ref Diff, but use only two colors (black if there is a difference and white if there is no difference)
- Navigation buttons:
- First frame: go to the first frame
- Previous frame: go to the previous frame
- Play/pause: start playback or pause, respectively
- Next frame: go to the next frame
- Last frame: go to the last frame
All buttons are duplicated by the appropriate items in the Playback menu. Hotkeys are also available for the buttons listed above. Please follow the main menu for exact hotkeys depending on the Operating System you use.
NOTE: The left or right area might not display any frame after navigation. This means that there is no corresponding frame in the appropriate file while the other file has a frame with the same frame number. This happens if opened files have different numbers of frames.
Quality Metrics View
The view consists of the following elements:
- Three tabs:
- Metrics: contains regular metric values for each file
- L/R Quality Diff: shows the difference between metrics of the left file and the right file
- RD Curves: contains RD Curves (if exist) as well as BD Rate information
- Metric combo-box to choose a metric to display on the main area. It could be one of the following:
- PSNR YUV, PSNR Y, PSNR U, PSNR V
- SSIM YUV, SSIM Y, SSIM U, SSIM V
- VMAF YUV, VMAF Y, VMAF U, VMAF V
- Run/Stop buttons are to start or stop, respectively, metrics calculation
The Run button is disabled if a reference file is not opened. Once the user clicks the Run button, it is replaced by the Stop button. And vice versa: once the user clicks Stop, or when the metrics calculation process is done, Run appears again, and replaces the Stop button.
Quality Metrics View can be hidden or shown by checking or unchecking Window > Metrics View, or by using hotkeys (Ctrl + Shift + M on Windows and Linux, or Cmd + Shift + M on macOS).
Once VQ Probe is launched, it has an empty project by default. You may open a project saved before, or, you can set up the project for your needs from scratch. To do so, start by adding source files.
Add Source Files
By source files we assume video files that are used in analysis and metrics calculation, as well as any other operations within VQ Probe. These could be uncompressed files as well as encoded files.
Source files can be added to the current project in several ways:
- Via Project View
- By pressing the "+" button on the Source Files panel of Project View. The standard system "Open Files" dialog will be opened. Select one or more files and press the Open button. Selected files will be analyzed then. If the files are valid and supported by VQ Probe, they will be added to the list of files. Otherwise, a message box with an error description will appear.
- By dropping files on Playback View. Files will be added to Project View
Now, when files are successfully opened, their information is displayed on the screen: codec, resolution, bitrate, framerate (the default value is 25), and frame count.
NOTE: Files must have the same resolution as well as the same chroma subsampling format.
Possible reasons why files cannot be added are:
- the files are not supported (please check the appropriate section for the list of supported formats)
- the files have different resolution and/or chroma subsampling format
- an internal application error
Remove Source Files
Select one or more files from the list on the Source Files tab and press the right mouse button. In the opened menu choose Remove.
Select Files Displaying
Use checkboxes from the Left, Right, or Ref columns to set the appropriate file to be displayed as the left, the right, or the reference file, respectively, on Playback View:
Create RD Curves
Press the right mouse button at any empty space or on any RD Curve item on the RD Curves tab. Choose Add RD Curve from the opened menu. Enter a name for a new RD Curve and press OK.
You cannot choose the name of any existing RD Curve. You cannot either choose the name of any already existed RD Curve. In both cases, you will be prompted to choose another name.
Remove RD Curves
Press the right mouse button on one or more RD Curves on the RD Curves tab, then choose Remove from the opened menu.
Add Source Files to RD Curve
Select one or more source files on the Source Files tab, then select the Add to RD Curve menu item. You will see the list of RD Curves where it's allowed to add the selected source files:
The selected source files from the example above cannot be added to AVC nor HEVC RD Curves because they are already added.
NOTE: A reference file cannot be added to an RD Curve.
Once you added source files to an RD Curve, they will appear in the list of RD Curves:
Remove Source Files from RD Curve
Choose one or more source files on the RD Curve tab, press the right mouse button, and choose Remove:
All the selected source files will be removed, even if they are referring to different RD Curves.
Set RD Curve as Anchor
An anchor RD Curve is used to calculate BD Rate. BD Rate will be calculated for all other RD Curves and relatively to the one marked as an anchor RD Curve.
To mark an RD Curve as the anchor, select that RD Curve and press the right mouse button:
Once marked, its name will be changed:
Opening YUV Files
Y4M files are opened automatically. In case of a regular YUV file, the user will be asked to specify video parameters, such as resolution, chroma subsampling, whether it's packed or planar, and bit depth.
Configure parameters of the file. Once a parameter is changed, the preview image updates. So, you can tune parameters until the image looks right to you.
NOTE: Once the user opened a specific file via the dialog, consequent openings of the same file will use the previous parameters as the default parameters.
For YUV/Y4M files you have the option to crop the image. This can be done in Open YUV File Dialog: There are 4 parameters to set up cropping:
- left: position in pixels where to start cropping horizontally
- top: position in pixels where to start cropping vertically
- width: width of the cropped area in pixels
- height: height of the cropped area in pixels
Once any of these parameters are changed, the cropped area visualization will be updated on the left side of the dialog.
NOTE: Cropping parameters will be automatically changed to the nearest multiple of 4 or 8 depending on the Plane Order. You may find the details under the information sign of the dialog.
You can trim source files by double-clicking on the First Frame or the Last Frame column for a specific source file. A spin box will appear:
Type in or select a required frame number and press Enter, or click the left mouse button outside the spin box. The value will be changed.
All first frame/last frame numbers that have been changed are marked in orange. For example, the first two source files below have the values that have been changed:
You can apply trimming to all source files. To do that, press the right mouse button on the First Frame or the Last Frame column for a specific source file and then choose either Apply First Frame Number to Others or Apply Last Frame Number to Others:
Once the option is chosen, all the files will be trimmed:
NOTE: Trimming source files will affect the frame numbering used in Playback View and Metrics View. For example, if a source file has been trimmed and now starts from Frame 10, then the frame marked as Frame 0 in Metrics View will correspond to Frame 10 from the original source file.
Playback can be started by clicking the appropriate Play button, by choosing the menu item Playback > Play/Pause or by using the hotkey Space. To stop playback, press the Pause button, choose the menu item Playback > Play/Pause or use the hotkey Space.
Framerate used for playback can be set to one of the values placed under the Playback > Framerate menu. The default value is 25 fps.
NOTE: Depending on hardware resources, video framerate of playback can be less than targeted in the menu.
YUV values of the opened files become available starting at a zoom ratio of 32x. These values will look as follows:
If the current visible component is chosen for displaying one plane (Y, U, or V), the values for that specific component will be shown. For example:
Use dec and hex switch to show values in decimal or hexadecimal formats, respectively.
Heat Map: Difference between Left(Right) and Reference
This mode allows you to visualize in the form of a heat map the difference between the left file's specific frame and the appropriate frame of the reference file as well as the difference between the right file's specific frame and the appropriate frame of the reference file.
Please choose L|R / Ref Diff (or View > Show Left/Right and Reference Difference from the main menu, or press F3 on your keyboard) to show the heat map. It looks as follows:
The color represents the difference between a specific pixel of the left (right) frame and a specific pixel of the reference frame, from 0 to the maximum difference:
For example, white color means there is no difference.
Once zoomed in to a zoom ratio of 32x and above, the values of the difference will be shown:
You may also choose a specific plane (Y, U, or V) to show the difference of a specific plane.
Heat Map: B/W Difference
This mode is similar to the previous one: the only difference is that in this mode VQ Probe uses only two colors: black (if there is a difference) and white (if there is no difference).
Please choose B/W Diff (or View > Show B/W Difference from the main menu, or press F4 on your keyboard) to show the black and white heat map. It looks as follows:
Again, once zoomed in to a zoom ratio of 32x and above, the values of the difference will be shown:
Video can be zoomed in as well as zoomed out. Following are the options:
- choose menu items View > Zoom In and View > Zoom Out to zoom in and zoom out, respectively
- use keyboard shortcuts
Specific key combinations depend on the Operating System the application is running on. You may find the exact shortcut combination in the View menu.
- press Ctrl and the left mouse button to start selection of the area to zoom to the specific area. Video will be zoomed in once the mouse button is released
There are some additional convenient functions:
- change the size to the actual video resolution by using View > Actual Size
- fit the video to the window's size by choosing View > Fit to Window in the menu
Video Quality Metrics
VQ Probe allows the user to calculate video quality metrics. The list of quality metrics is provided in section Supported Video Metrics.
The functionality of video quality metrics calculation is available on Metrics View.
Once at least one target file is opened, and the reference file is opened, VQ Probe is ready to calculate video quality metrics. The user can do that in one of the following ways:
- by clicking Metrics > Run in the main menu
- by clicking Run in Metrics View
- by using hotkeys: Cmd + M, Cmd + R (macOS) or Ctrl + M, Ctrl + R (Windows, Linux)
Next, metrics calculation starts for every available metric: PSNR, SSIM, and VMAF. Values appear immediately:
The Run button is disabled if there is no reference file opened.
The Run button is replaced by the Stop button during the metrics calculation process.
The currently visible metric can be changed via the Metric combo-box.
The user can see exact numbers for a specific frame by moving the cursor over a graph. A tooltip will show the frame number and metric values for that frame.
You can navigate by clicking on a specific frame in Metrics View. After that, the actual image(s) in Playback View will be changed according to the selected frame.
Similarly, once the current frame is changed in Playback View, the current frame selection in Metrics View will be changed.
The following hotkeys can be used to zoom in or out on graphs in Metrics View:
- Left mouse click will start a custom rectangle selection; zooming is applied once the button is released
- Right mouse click will zoom the graph back to default
- Shift + mouse scroll will zoom the graph by both X and Y Axes
- Cmd + mouse scroll (macOS) or Ctrl + mouse scroll (Windows, Linux) will zoom the graph by the X Axis
The L/R Quality Diff tab allows the user to get the difference between the metrics of the right file and the metrics of the left file. In other words, it shows how much the right file is better than the left file:
The values on the graph will be negative if the right file is of a lower quality than the left file. For example:
RD Curves tab allows you to plot RD Curves as well as calculate BD Rates. Please make sure you set up the RD Curve list (please refer to Project section).
Once all metrics are finished, RD Curves will appear on the appropriate tab:
The tab contains the following information:
- BD Rates: the list of BD Rates. The first RD Curve is assumed as the anchor. BD Rates for other RD Curves are calculated in relation to the anchor RD Curve
- RD Curve plot: a plot that consists of points, each of them is an average appropriate metric value at a specific average file's bitrate
Changing the Metric combo-box will change the current RD Curves plot to a plot for the selected metric.
- While using 4K+ resolution, the "+" button in Project View is too small.
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Third Party Libraries
VQ Probe uses certain 3rd party libraries, as listed below. You may find the full text of each license in the following folder: Windows/Linux – the licenses folder under your application's folder; macOS – vq_probe.app/Contents/SharedSupport/licenses.
Qt is licensed under the GNU Lesser General Public License (LGPL) version 3.
Project homepage https://www.qt.io/, upstream version: 5.13.1.
Copyright (C) 2019 The Qt Company Ltd and other contributors
You may find the full text of the license in the Qt_license file of your binary package.
Qwt is licensed under the Qwt License, Version 1.0.
Project homepage https://qwt.sourceforge.io/, upstream version: 6.1.4.
Copyright (c) 2019 Uwe Rathmann
You may find the full text of the license in the qwt_license file of your binary package.
FFmpeg is licensed under the GNU Lesser General Public License (LGPL) version 2.1.
Project homepage https://ffmpeg.org, upstream version: 4.2.2.
Copyright (c) 2000-2019 the FFmpeg developers
You may find the full text of the license in the ffmpeg_license file of your binary package.
Libvmaf is licensed under the BSD+Patent License.
Project homepage https://github.com/Netflix/vmaf, upstream version: 1.3.16.
Copyright (c) 2020 Netflix, Inc.
You may find the full text of the license in the libvmaf_license file of your binary package.
VVCSoftware_VTM is licensed under the BSD License.
Project homepage https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/-/tree/VTM-10.0, upstream version: 10.0.
Copyright (c) 2010-2020, ITU/ISO/IEC
You may find the full text of the license in the libvvc_license file of your binary package.
dav1d is licensed under the BSD 2-clause "Simplified" License.
Project homepage https://code.videolan.org/videolan/dav1d, upstream version: 0.7.1.
Copyright © 2018-2019, VideoLAN and dav1d authors
You may find the full text of the license in the dav1d_license file of your binary package.
NumCpp is licensed under the MIT License.
Project homepage https://github.com/dpilger26/NumCpp, upstream version: 2.3.1.
Copyright (c) 2020 David Pilger
You may find the full text of the license in the NumCpp_license file of your binary package.
Boost is licensed under the Boost Software License, Version 1.0.
Project homepage https://www.boost.org, upstream version: 1.74.0.
You may find the full text of the license in the Boost_license file of your binary package.