Video Quality Metric (VQM) Software
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Frequently Asked Questions (FAQ)
Question: "What are the Video Quality Models (VQM)?"
Answer: The Video Quality Project has been developing
objective Video Quality Models (VQM) for over two decades. Our VQM
software offers an inexpensive alternative to subjective tests.
VQM is a standardized method of objectively measuring video
quality. VQM's ratings closely predict the subjective quality
ratings that would be obtained from a panel of human viewers.
End-users and service providers can use VQM tools to:
- specify/verify system performance
- compare competing service offerings
- maintain and monitor the quality of their networks
- optimize the use of limited network resources such as
Due to its excellent performance in the International Video
Quality Expert's Group (VQEG) validation tests, the NTIA/ITS VQM
methods were adopted as ANSI and ITU standards. VQM tools are available for
the Windows® operating systems and customized for two different
applications: batch processing and command line
Question: "What usage restrictions does the VQM software
Answer: The VQM software can be downloaded
royalty free. The VQM
software can be used for any commercial or
non-commercial use. VQM software are
available for both the Windows operating systems. MATLAB source
code is provided for most of the VQM tools.
Question: "Is VQM available for Linux or OS?"
Answer: No. We do not have a Linux or OS compatible
executable for the VQM software. However, you can download the VQM
source code and run it on MATLAB®.
Question: "Where can I find free source video sequences
for research and development?"
Answer: See the Consumer Digital Video Library
Question: "Which calibration option should I
Answer: If you do not know anything about your codec's
calibration, here are our suggestions. Run BVQM twice: once
with 'Reduced Reference Calibration Version 2' and once with 'Full
Reference Calibration'. Both of these calibration options
check everything. 'Full Reference Calibration' is more accurate but
does not check for spatial scaling. 'Reduced Reference Calibration
Version 2' will check whether or not your codec is spatially
scaling the video.
Question: "Which model should I choose?"
Answer: The VQM software has a variety of algorithms to
suit different needs:
- The NTIA General Model
- NTIA Fast Low Bandwidth Model
- Video Quality Model with Variable Frame Delay (VQM_VFD)
- The Peak Signal to Noise (PSNR) Model
The NTIA General Model and the Full
Reference Calibration were validated and standardized.
Click here for
a description, or here for a
full disclosure. The NTIA General Model is often called "VQM" in
literature. It is more accurate than PSNR. Thiese algorithms weres
trained mostly on standard definition video and a few CIF videos
(352x288 pixels). The NTIA General Model is effectively a full
The NTIA Fast Low Bandwidth Model and
the Reduced Reference Calibration were
validated and standardized. The NTIA
Fast Low Bandwidth Model is a reduced reference model with
similar performance to the NTIA General Model. Currently, all
implementations of this model are full reference.
The Video Quality Model with Variable Frame
Delay (VQM_VFD) was released late in 2011. This is
the most accurate ITS VQM to date. VQM_VFD includes a neural
network that was trained on people's opinions of the
quality of 11,255 test videos. These videos ranged in
resolution from cell phone size to HDTV. This model has not
been validated or standardized. Click here for more information.
The PSNR Model has wide industry acceptance yet
limited accuracy. PSNR is very sensitivity to calibration
errors. If you want to use PSNR on video that may contain
a reduced frame rate or variable frame delay and you want this
effect removed before PSNR is calculated, we recommend 'PSNR
with Variable Frame Delay'. PSNR is less accurate than the
NTIA General Model and the Fast Low Bandwidth Model for most
Question: "How should I refer to these models in
U.S. Department of Commerce policy prohibits NTIA/ITS
from endorsing products.
Preferably, refer to the National or International Standards associated
with the video quality model. This gives legitimacy and credence to
- The NTIA General Model and Full Reference
Calibration were standardized identically in all three
Recommendations (ANSI T1.801.03-2003, ITU-T Rec. J.144, and
ITU-R Rec. BT.1683).
- The Fast Low Bandwidth Model and Reduced Reference
Calibration were standardized in separate Recommendations
(ITU-T Rec J.249 and ITU-T Rec. J.244).
- An exhaustive search version of PSNR was standardized by
ITU-T (ITU-T J.340). This model is very slow, yet compute ideal
values for a constant spatial shift, constant temporal shift, and
constant luminance gain and offset. This model can be computed by
selected one of the PSNR search calibration options, followed by
the PSNR model. Do NOT choose the PSNR_VFD model, which also
includes advanced variable frame delay estimation.
Question: "I ran CVQM and nothing happend."
Answer: CVQM does not print anything to the command
line. The results are written to log files, named after the
processed video file.
Question: "I am confused by CVQM's log file. I ran the
General Model, and looked in the log file. To check the
result, I calculated the VQM based on 7 parameters by using this
equation as your
This was different than the value listed next to "general" in
the CVQM log file. Why?"
Answer: The parameter values in the CVQM log file
already have the weight applied. Sum these parameter values,
and you will get the number listed next to "general" (i.e.,
the NTIA General Model). This model is called "VQM" in the
Question: "What references should I use for the NTIA
NTIA General Model (also known as VQM), Developer's
model and the Full Reference Calibration
algorithms: An NTIA
Technical Report contains a full disclosure of these
algoirthms, while an IEEE
journal article provides a more easily
The NTIA Fast Lowbandwidth model is described in this ITU Contribution. A
VPQM conference paper
provides a more easily understood summary, but this paper is
missing some details. The Reduced Reference calbiration algorithms
are fully disclosed in an NTIA Technical Report.
The VQM_VFD model is described in an NTIA Technical