An Experimental Analysis of Objective Video Quality Assessment Methods

8/17/2019 An Experimental Analysis of Objective Video Quality Assessment Methods

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Università degli Studi di Modena e Reggio EmiliaFacoltà di Ingegneria “Enzo Ferrari”

Corso di Laurea Specialistica inIngegneria delle Telecomunicazioni

An ExperimentalAnalysis of

objective video

quality assessmentmethods

Relatore:

Prof. Ing. Maria LuisaMerani

Tesi di:

Luciana agnetta

Anno Accademico!"##$!"#!



!at is "oE#%uality of Experience describes the &quality from

the perspective of the user or consumer 'i.e.vie(er)* (ith a focus on the perceived quality ofthe content 'or more comprehensively* userexperience).+ ',in-ler)

$o% to measure &ideo "oE#hrough /ideo %uality Assessment '/%A)methods* i.e. methods that calculate the value ofa quality metric '/%M)* an index that representsthe level of quality of a video .



Su'(ective vs o'(ective &") *+,-.

0ubjective /%A methods

Pros1 accurate and reliable

ons1 expensive and timeconsuming



2bjective /%A methods

Su'(ective vs o'(ective &") *-,-.

Pros1 cheap and fast.

ons1 their performance cannot be evaluated (ithout asubjective benchmar-3 usable only for codec evaluation3either inaccurate or computationally expensive.



#. Experimental based comparative analysisof exististing objective /%A methods

!. haracteri4ation of the ontent type of

videos through the calculation ofomplexity and Motion factors

5. Introduction of a ne( Prediction Modelfor /%A

Main Contri'utions



Met!od

#" ra( yuv videos representing natural scenesencoded at #" di6erent bit rates 'for a total of#"" test videos) (ith 7.!89$A/ scheme

0oft(are implementation of #" objective

/%A methods

Available subjective scores for each of the#"" videos 'research of :$e university(here I (or-ed on my master project)

Performance evaluation of each methodusing as benchmar- the subjective scores



+/ 0ormalized &"M results *+,-.he quality of each impaired video (as calculated (ith each/%Ms using the correspondent ra( video as reference.



+/ 0ormalized &"M results *-,-.



-/ C!aracterization o1 t!e Content T2pe *+,-.

, 0 ≤ C

≤1

, 0 ≤ M

≤1

(here ;itsI are the bits of coded Intra 'I<)

frames* ;itsP are the bits of coded Inter 'P<)

frames* %PI is the average quanti4ation

parameter of I<frames and %PP

is the

average quanti4ation parameter of P<frames. and M factors depend on readily availableparameters* thus they can conveniently beemployed by a non<intrusive video contentblind quality model



-/ C!aracterization o1 t!e Content T2pe *-,-.



&ideos %it! Lo%est )verage measured 3ualit2

&ideos %it! $ig!est )verage measured 3ualit2

he ! videos (hich havethe lo(est averagemeasured quality accordingto all metrics are also theones (ith the highest levelof motion and complexity.

he videos (ith the

highest averagemeasured quality arealso the ones (ith thelo(est level of motionand complexity.



4enc!mar5ing o1 6'(ective &") met!ods

=ormali4ation of the output of each /%M

>itting of normali4ed values vs ;it ?ate foreach /%MPerformance of 2bjective /%A (ith respectto subjective results is evaluated by t(omain attributes 1



7/ T!e ne% 8rediction Model *+,7.

he model used to ma-e the prediction ofvideo quality is the follo(ing asymptoticexponential function1

(here a is set to # for ensuring theconvergence of the maximum quality

index to #3 and M are the formerlypresented complexity and motionparameters3 ;r is the bit rate3 b* c and dare the parameters optimi4ed for a

generic video type.



7/ T!e ne% 8rediction Model *-,7.



7/ T!e ne% 8rediction Model *7,7.



My metric provides a good trade<o61

computationally comparable to existing@simple 'yet inaccurate) metrics3

comparably as accurate as M2/IE '(hich isunviable due to high computational

requirements).

ConclusionsExisting /%Ms are either inaccurate or

computationally and memory intensive.

Existing /%Ms are either inaccurate orcomputationally and memory intensive

My metric can be used not only for codecevaluation but also for real timeapplications because it depends on

readily available parameters.



Extend tests to net(or-<impaired videos

Future or5

onsider broader test matrix

>urther study the t(o cases in (hichne( metric does not correlate (ell(ith M2/IE

An Experimental Analysis of Objective Video Quality Assessment Methods

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