Video Quality Monitor
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Video Quality Monitor (VQM) is the most flexible solution to measure and monitor the video quality perceived by end-users (also called QoE: Quality of Experience).
VQM enables:
- perceived video quality measurement of video files
- perceived video quality monitoring of a live video source in real time
- measurement of blockiness (sometimes called "blocking effect"), blur (sometimes called "blurring"), contrast, jerkiness (sometimes called "image freezing"), bitrate
- audio loudness measurement and monitoring according to recommendations ITU BS 1770-2 and EBU R128
- video decoders (Set Top Box) testing
- monitoring of file-based encoding (example: encoding for VOD)
VQM can process several files in parallel. This is particularly useful to process a large number of files (using the Watch Folder for example). VQM can even test the decodability of audio and video at about 40x speed (on a simple PC) and count the number of decoded audio samples and video frames. And if these values are different than the expected values (based on header information), VQM can send you alerts.
VQM is a software product. It works under Windows (XP, Vista, Seven) and is easy to install (especially if you just want to use the no reference metrics, in this case you just have to run the installer and click on "Next..." several times). It can run on virtually any PC. It can even run on a laptop. If possible, the recommended configuration is: 4-core CPU, 3 GB of RAM, 10 GB of free hard disk space.
VQM supports lots of different sources: video files, capture cards (SDI, Composite, etc.), external devices and IP streaming in UDP or RTP. VQM includes no reference, parametric and hybrid video quality metrics. It means that when you want to measure the perceived video quality of a distorted video, you just have to provide this video. For parametric and hybrid metrics, the video must be in a compressed format.
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Starting VQM
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At start up, VQM displays a window showing a preview frame of the tested video (the video that you want to measure). To start using VQM, you generally use the "offline mode", click the "Browse..." button in order to select a video file and load it. But VQM can also measure in real time the quality of video being captured live: that's the "online mode". In this case, VQM can process audio and video from IP streaming or from audio video capture devices (like a Blackmagic Design card for example). VQM supports MPEG-2 and MPEG-4/AVC (H.264) in the most used containers: AVI, TS, MP4, PS, ES, etc... In fact, you can choose between using the integrated decoders or using DirectShow decoders. So if you can play your video files in a media player (like Windows Media Player, or Media Player Classic, etc...), then you can use VQM with these files. Videos can have any duration, any frame rate and any frame size. VQM also supports uncompressed YUV formats (4:2:0 planar, 4:2:2 planar, 4:2:2 UYVY, 4:2:2 YUYV, 4:4:4 planar). And if your videos are Multi Program Transport Streams (MPTS), you can select the audio and video streams that you want to process. Show more Hide |
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Videos loading
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Once a video is loaded, its first frame is displayed. The parameters of its video and audio streams are also displayed: codec, frame dimensions, frame rate, number of frames, duration, audio sampling rate, audio duration, etc. For real time monitoring, the "online" mode enables to choose the source between IP streaming and DirectShow compatible capture devices/cards. If one or several parameters were badly parsed from the file (this happens sometimes with non-standard compliant applications or broken files), all the parameters can be manually forced. And if you need to crop a video in order to remove black bands or to select only a part of the image, it can be done manually or automatically. The interface also supplies a slide bar to seek to a particular frame. You also have buttons that enable you to view a given frame or play the video. Show more Hide VQM's graphical user interface also displays many useful information. In fact, all the parameters that you could need are displayed and are editable. Since VQM only needs the video under test (and doesn't need its reference video), it is very simple to use. You just have to select the appropriate metric, load your file and start the video quality measurement. Show more Hide |
Measuring the perceived video quality
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During video quality measurement, several windows can be displayed: measured video frame, quality curves and video bitrate curve. The estimated remaining time is also displayed, along with a progress bar. Of course, measurement can be paused or stopped . On the presented screenshot, three quality curves are displayed. Don't worry: all is explained in the help and in the generated analysis reports. Just click the "help" button. Show more Hide In parallel of quality measurement, the instant video bitrate is measured for each frame. The quality measurement step uses multithreading. So the more CPU cores you have, the faster VQM works. When the quality measurement step is finished, the shape of the perceived video quality curve (versus time) is known. So the minimum and maximum quality scores are known. Then the "characteristic frames" (the most disorted frames and the less distorted frames, determined thanks to adaptive thresholds that can be defined by the user) are saved in uncompressed format so that they can be consulted later, even if the video file has been moved or deleted. And don't worry: you won't get out of disk space due to the saved images. In fact, all file saving operations in VQM are controlled by size quotas on folders: when the size quota is reached for a folder, its older files are deleted. Show more Hide |
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Web server
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When you've done that (selecting a video quality metric, loading a video, starting the quality measurement step and waiting its completion), the perceived video quality score is displayed, expressed in MOS (the signification of MOS values is fully explained in the help). That's good but the best is yet to come... VQM includes its own web server. There is no need to install a separate server (like Apache): VQM's web server is already fully included in the application. This web server enables you to connect from anywhere and get the measurement results, statistics, curves and even quality analysis reports (in several formats, including HTML format so that you can copy/paste it or load it in your favorite word processor, like Microsoft Word for example). To connect to the web server, all you have to do is opening a web browser (Internet Explorer, Mozilla Firefox, Chrome, Safari, Opera...) and go to URL "http://IPADDRESSOFTHEMACHINE" (replace IPADDRESSOFTHEMACHINE by the IP address of the machine which runs VQM). On the local machine (that runs VQM), you can use the URL "http://127.0.0.1" to display the web interface. By default, the web server uses port 80 but if you already have a server listening on port 80, you can change this port number. The first page of this web interface is the main menu which proposes different choices. Show more Hide |
Results
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In the main menu, the most frequently selected choice displays the list of processed videos. In this list, each video is represented by a unique number, its test campaign (that enables to gather several results), its file name, its full path, the description of its video and audio streams (codec, dimensions, frame rate, duration, etc...), its video quality score and statistics on video quality (min, max, standard deviation). For each video, several links enable you to display the quality curves, the bitrate curve, the characteristic frames. Some other links permit to draw various representations of the perceived quality versus the bitrate. At last, some links allow to generate perceived video quality analysis reports in various formats (CSV, TXT, HTML). |
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Curves
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In the web interface, all curves are interactive: if you click on one point of the curve, it will put this point at the center and zoom by a factor of 2. And if you drag your mouse to select a portion of the curve, it will zoom on this selection. If the frame corresponding to the center of the curve is a characteristic frame, then this frame will be displayed below the curve. You can also get graphical representations of the perceived quality versus the bitrate. This will enable you to determine the bitrate which is required to get a given quality level. |
Audio
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VQM can also measure:
The measurements are made on the decoded audio waveforms and VQM supports the most common audio formats. To use a particular format, you'll just have to install the appropriate audio decoder. In the main interface, a button enables to manually reset the audio breaks counter. |
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Loudness
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VQM can measure audio loudness according to international recommendations ITU BS 1770-2 and EBU R128. This loudness measurement computes 5 different values:
Loudness can be computed in both online and offline modes. This permits to monitor loudness in real time but also to measure loudness from captured signals (like audio video recordings). Like the other measured data, all measured loudness values are saved and can be retrieved thanks to the web interface. VQM can also trigger alerts if loudness is greater than a user-defined threshold. At last, the integration durations for short term, medium term and gated loudness can be modified by the user. |
Other features
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VQM contains lots of other features, among which:
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Conclusion
Enabling to work in both offline and online (real time) modes and with its elaborate quality metrics, VQM is definitely the solution that will adapt itself to answer your needs for video quality measurement and monitoring. Ask for an evaluation version today!
If you are interested by VQM but if you have only a punctual need or if you don't have the necessary manpower to fully exploit one license, please note that we also propose consulting services based on the use of VQM.
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