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Netflix VMAF. How to measure video quality with VMAF in Zond

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Zond 265 4.4

HEVC Video Analyzer

File info: 39.81 Mb, 2018 Nov 20

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About a VMAF metric

How to measure video quality with VMAF in Zond 265

 

About a VMAF metric

Starting with the version 4.1 of Zond 265, we added the Video Multimethod Assessment Fusion (VMAF) quality metric support. The VMAF metric, developed by Netflix, now appears to have displaced older methods like Peak Signal-to-Noise ratio (PSNR) in Netflix workflows.

The existing metrics, such as PSNR and SSIM do not reflect human perception and Netflix found that "these metrics fail to provide scores that consistently predict the DMOS ratings from observers". DMOS is Differential Mean Opinion Score, the human score achieved in subjective testing.

The new metric works by combining multiple elementary quality metrics and fusing them together with a machine-learning algorithm, specifically a Support Vector Machine (SVM) regressor. The three elementary metrics are:

  1. Visual Information Fidelity (VIF)
  2. Detail Loss Metric (DLM)
  3. Motion

How to measure video quality with VMAF in Zond 265

  1. Launch Zond 265 and open the file
  2. Go to the "Quality" tab
  3. Push "Open reference file" and select file with YUV data

  4. image1

    Figure 1. Open reference file button in the "Quality" tab.

  5. To calculate VMAF value for current frame press "Calculate" button. VMAF metric will be calculated for all frames in current GOP and displayed with the green solid line on timeline, as shown on the Figure 2. VMAF value displays in Quality tab.

  6. image3

    Figure 2. Calculating VMAF value for current frame.

  7. Clicking the "Press to parse all frames" button starts the metrics' calculation for the entire file. VMAF will be calculated for all frames, as it shown on the Figure 4. Also you can obtain these values selecting the "Quality" from the Bars chart pop-up menu and specifying the path to the reference file.

  8. image4

    Figure 3. Bars chart menu.

    image5

    Figure 4. Calculating VMAF value for all frames.

  9. In order to generate the text report containing VMAF values, you need to select "VMAF" checkbox under the "Quality" section (Figure 5).

  10. image6

    Figure 5. VMAF Quality option.

    As a result, you'll get the report in either CSV or JSON format. See below the examples of output reports.

    image7

    Figure 6. Report examples.


 
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