1. Quality Evaluation and Comparison of SVC Encoders 371-10-21
Esti Hagag, Maayan David
Dr. Ofer Hadar; Dan Grois

2. Introduction Video coding: H.264 AVC & SVC
SVC or scalable video coding is an extension of the H.264 standard. SVC offers scalable video streams which can be displayed on various devices with different display resolutions, computation capabilities and bandwidth limitations.

3. Introduction Cont.
Spatial Scalability: the base layer contains a reduced size of the original video sequence. Each additional layer enhances the resolution, resulting in a greater video image with higher resolution. This is intended for devices that have different displaying capabilities i.e. small screens cell phones.
Temporal Scalability: The base layer is a low frame-rate version of the original video and each additional layer adds more frames resulting in a higher frame-rate of the video.

4. Introduction Cont.
Quality: All layers have the same spatial resolution. Each layer adds to the quality of the video image which is determined by the available bit-rate or computational capabilities of the end device.

5. Project Goal
Evaluation and comparison of encoders that exists in the industry in order to determine the most suitable SVC based encoder in terms of quality metrics and computational complexity. Different quality metrics are tested to see which metric is the most accurate for quality evaluation.

6. Quality Metrics
Many types of metrics are available for evaluating video quality. The graphs below represent only a few metrics from the total we’ve used for analysis and evaluation. Such metrics are:
APSNR - Average Peak Signal to Noise Ratio
OPSNR - Overall Peak Signal to Noise Ratio
MSE - Mean Squared Error
MSAD - Mean Sum of Absolute Difference
NQI - New Quality Index
VQM - Video Quality Measurement Techniques
SSIM - Structural Similarity
Delta - Average difference between 2 sequences

7. Quality Metrics Cont.
APSNR - Average Peak Signal-to-Noise Ratio Calculating PSNR values for all frames and averaging them. Advantages: If all video frames have similar complexity, APSNR is quite accurate. Disadvantages: If a few frames score much higher PSNR, this could effect the total PSNR value for all frames.

8. Quality Metrics Cont. Example
Codec A:
Frame 1, every pixel has a squared error of 100, PSNR for this frame is 20*log(255/10) = dB
Frame 2, every pixel has a squared error of 100, PSNR for this frame is 20*log(255/10) = dB
Frame 3, every pixel has a squared error of 100, PSNR for this frame is 20*log(255/10) = dB
Frame 4, every pixel has a squared error of 100, PSNR for this frame is 20*log(255/10) = dB
Frame 5, every pixel perfect with 0 error, PSNR for this frame is Infinite. we can use a max =100
Average PSNR= ( )/5 = 42.50dB
Codec B:
Frame 1, every pixel has a squared error of 80, PSNR for this frame is 20*log(255/10) = dB
Frame 2, every pixel has a squared error of 80, PSNR for this frame is 20*log(255/10) = dB
Frame 3, every pixel has a squared error of 80, PSNR for this frame is 20*log(255/10) = dB
Frame 4, every pixel has a squared error of 80, PSNR for this frame is 20*log(255/10) = dB
Frame 5, every pixel has a squared error of 80, PSNR for this frame is 20*log(255/10) = dB
Average PSNR = dB

9. Quality Metrics Cont.
OPSNR - Overall PSNR Here we average the MSE for all frames and then calculate the PSNR using the average MSE Codec A: mean squared error = (100 * * 1)/5 = 80 Overall/global PSNR = 20*log(255/sqrt(80)) = dB Codec B: Overall/global PSNR = 20*log(255/sqrt(80)) = DB

10. Quality Metrics Cont. MSE - Mean Squared Error
Advantages: Simple and gives the strength of error between to values. A rough estimate between two compared images
Disadvantages: Results doesn’t reflect quality in terms of the HVS

11. Quality Metrics Cont. MSAD
The value of this metric is the mean absolute difference of the color components in the correspondent points of image. This metric is used for testing codecs and filters.

12. Quality Metrics Cont. Delta
The value of this metric is the mean difference of the color components in the correspondent points of image. This metric is used for testing codecs and filters.

13. Quality Metrics Cont. VQM - Video Quality Measurement Techniques
VQM uses DCT to correspond to human perception.

14. VQM vs. MSE

15. Quality Metrics Cont. SSIM - Structural Similarity Index
SSIM Index is based on the measuring of three components: luminance similarity, contrast similarity and structural similarity.

16. Quality Metrics Cont. NQI - New Quality Index
Objective quality factor composed of three different factors:
Loss of correlation
Luminance distortion
Contrast distortion
Range is [-1,1] where value 1 is the highest and is achieved if and only if the source and tested images are the same.

17. Software Encoders VSoft - Vanguard Software Solutions
VSoft’s AVC Professional SDK
offer the ability to integrate VSoft’s video compression technology into a wide array of applications.
Support for Windows, Mac OS X and Linux development.
Ideal for
High-quality broadcasting
Video conferencing
Surveillance
Real-time applications

18. Software Encoders Cont.
Features
Fourth-generation VSoft H.264 codec implementation, unparalleled in compression ratio, video quality and code efficiency.
SD and full HD encoding in real-time on off-the-shelf PC systems!
Fully standard-compliant H.264 codec with support for Baseline, Main and High Profiles of the H.264 standard, as well proprietary enhancements.
Scalable Video Coding (SVC) implementation for multiple-resolution profiles.

19. Software Encoders Cont.
JSVM - Joint Scalable Video Module (OpenSource)
The JSVM software is the reference software for the Scalable Video Coding (SVC) project of the Joint Video Team (JVT) of the ISO/IEC Moving Pictures Experts Group (MPEG) and the ITU-T Video Coding Experts Group (VCEG). Since the SVC project is still under development, the JSVM Software as is also under development and changes frequently.
The JSVM software is written in C++ and is provided as source code.

20. Software Encoders Cont.
Elecard Video Quality Estimator
A software tool for testing and comparing video sequences
Calculates video quality metrics (PSNR, NQI, VQM, SSIM, DELTA, MSE, MSAD)

21. Configuration & Settings
Several sequences were taken in different resolution:
QCIF: 176x144
CIF: 352x288
4CIF: 704x576
HD: 1280x720
Sequences with fast/slow moving objects
Input video format: YUV 4:2:0
Spatial Scalability was chosen for SVC encoding.
Layer #0 QCIF
Layer #1 CIF
Layer #2 4CIF
Constant BR mode

22. Evaluation & Results
“Station” is video that is a zoom-out of a train station. Therefore there are many motion vectors and new objects appearing from the borders of the frame.
We have encoded the sequences in SVC spatial scalability mode with 3 resolution layers with the following bitrates:
Layer #0: 230 Kbps
Layer #1: 680 Kbps
Layer #2: 2048 Kbps
JSVM was better in almost all tests that were done and outputs greater image quality than the VSoft encoder. VSoft is built to be a real-time encoder unlike the JSVM encoder and it has more time constraints that can affect quality.

23. Evaluation & Results

24. Evaluation & Results Cont.

25. Evaluation & Results Cont.

26. Evaluation & Results Cont.

27. Evaluation & Results Cont.
The next sequence was encoded in AVC mode, HD resolution of 1280x720 characterized by a small amount of motion vectors
Several bitrates were tested:
500 Kbps
1750 Kbps
3500 Kbps
The results show that both encoders are very much alike. The differences in quality was very little and it’s not possible to determine which encoder is better in terms of quality.

28. Evaluation & Results Cont.

29. Evaluation & Results Cont.

30. Evaluation & Results Cont.

31. Evaluation & Results Cont.

32. Evaluation & Results Cont.
The next tests were done on a sequence with many motion vectors with little new objects appearing during the sequence.
The sequences are in 3 different resolutions and bitrates:
QCIF 176x144
80 Kbps
264 Kbps
448 Kbps
CIF 352x288
160 Kbps
524 Kbps
896 Kbps
4CIF 704x576
320 Kbps
1184 Kbps
2048 Kbps

33. Evaluation & Results Cont.

34. Evaluation & Results Cont.

35. Evaluation & Results Cont.

36. Evaluation & Results Cont.

37. Conclusions Better Stream with a slow motion - VSOFT
Stream with a slow motion - JSVM
Quality Tools
JSVM
APSNR
OPSNR
0.7621
NQI
0.7375
VQM
0.9619
SSIM
VSOFT
Delta
MSE
5.3409
MSAD

38. Conclusions Cont. Better Stream with a fast motion - VSOFT
Stream with a fast motion - JSVM
Quality Tools
JSVM
APSNR
OPSNR
0.5502
NQI
VQM
SSIM
VSOFT
Delta
MSE
MSAD

39. Conclusions Cont. Both encoders delivers similar quality results.
JSVM is better in sequences with high rate of change and many motion vectors
JSVM can deliver almost the same quality as VSoft with smaller bitrates
VSoft is more efficient in terms of memory consumption and run time and can deliver good quality in a short time.

40. Future Work Perform evaluation tests on hardware based encoders
Acquiring more encoders to evaluate