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Automated Testing Tools For

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An automated accessibility tool is a piece of software which can test a web page, or even an entire website, for accessibility. Automated accessibility tools are useful because they can save you a huge amount of time. Don't want to check images for alt text on each and every page on your website? Run the site through an automated tester and it'll do it all for you!

Automated accessibility testing tools have been around for a long time and have historically been a useful way of checking websites for accessibility. Bobby, one of the first and most well-known automated accessibility testing tools, is now almost 10 years, and although is no longer freely available, plenty of other free tools such as WebXact (http://webxact.watchfire.com/) and Wave (http://wave.webaim.org/index.jsp)do exist.

But are these tools a little too good to be true? Can you test a website for accessibility so easily? Unfortunately the answer is a resounding no. There are a number of underlying problems associated with using just automated tools to test for accessibility:

Literal interpretation of guidelines

Any automated accessibility testing tool, being a piece of software, doesn't have very much in the way of common sense. It will interpret each and every accessibility guideline literally, without bearing any other thought to what else is on the page.

The definition of the word guideline, according to Dictionary.com, is "a rule or principle that provides guidance to appropriate behaviour". A guideline simply offers guidance to what the best practice is - it shouldn't just be applied without regard to other factors.

For example, one of the W3C accessibility guidelines states that a table summary should be provided for all tables. (This summary doesn't appear on the screen, but it's read aloud to screen reader users before reading through the table content.) Table summaries are useful as they tell screen reader users what to expect in the table. However, there may be a heading directly before the table and it describes what the table is about. In this instance, this summary is essentially useless as it will just repeat what the previous heading said.

Can't check any content issues

The way that content is structured both on the page and across the website is a massive part of accessibility. A website may be perfectly coded and conform to the highest coding standards. If its content is poorly structured though, the site will prove difficult to impossible for some special needs web users.

There are a number of important accessible content considerations, none of which automated accessibility testing tools can check for. Some of these important considerations include:

- Front-loading content so that each paragraph begins with the conclusion

- Ensuring content has been broken down into manageable chunks with descriptive sub-headings

- Using lists wherever appropriate

- Ensuring that plain and simple language is used

Can't check many coding issues

The vast number of accessibility guidelines tend to be related to how the site is coded. Automated accessibility testing tools are unfortunately unable to test for many of these too. Examples of HTML-related accessibility considerations which these tools can't check for include:

- Ensuring that text is real text and isn't embedded within images

- Making sure that the site functions without the use of JavaScript or Flash

- Providing equivalent text links if using server-side image maps

- Ensuring that the structure within the HTML reflects the visual appearance (e.g. headings are labelled as headings within the HTML code)

Outdated guidelines are used

Automated accessibility testing tools generally use the W3C accessibility guidelines, which by now are over five years old. As such, a number of these guidelines are outdated and don't apply anymore. In fact, some of them are now thought to hinder accessibility rather than help, so it's best to totally ignore these guidelines.

For example, an automated accessibility testing tool will probably insist that form items contain default place holding text. It may also insist that links need to be separated by non-link text. Neither of these guidelines are relevant anymore and their implementation could make accessibility worse rather than better.

Most guidelines aren't properly checked

Automated accessibility tools can check for a number of guidelines, and can tell you when a guideline isn't being adhered to. However, when the tool claims that a guideline is being fulfilled this may in fact be a false truth.

For example, if all images contain alt text then the software will report a pass for this guideline. But what if the alt text isn't descriptive of its image? What if alt text is crammed full of nonsensical keywords for search engines? How can an automated accessibility tool possibly know this?

Warnings may be misinterpreted

The reports generated by automated accessibility tools provide warnings, as well as errors. These warnings are basically guidelines that the automated tool can't check for, but which may be errors. Often they're not, and in fact they're often not even relevant. However, some people reading a report may try to get rid of these warning messages by making the appropriate changes to their site. By doing so, they may be implementing guidelines that needn't be implemented and inadvertently lowering the website's accessibility.

Conclusion

Automated accessibility testing tools can be useful as they can save a large amount of time in performing some very basic checks for accessibility. However, they must be used with caution and they cannot be used as a stand-alone guide for accessibility checking. Indeed, some expert accessibility knowledge should always be applied in evaluating a site accessibility, perhaps in conjunction with the fantastic web accessibility toolbar (http://www.nils.org.au/ais/web/resources/toolbar/) to help dramatically speed up manual checks.

Automated Testing Tools For

Over the next decade, it is expected that digital television penetration into the general television market will increase from less than 5% in 2003 to more than 50% by 2010.

Currently, the FCC requires that 50% of televisions 36 inches or larger have integrated digital capability by July 2005. By July 2007, the FCC will require that all new televisions 13 inches or larger must incorporate a digital tuner. Obviously the FCC's ruling provides additional fuel for the growth of the DTV market.

So testing is increasing important. The test setup simply stated is

* Start with a known video sequence.

* New Video Processing system alters the video sequence.

* Decode the processed video sequence.

* Capture the processed video sequence.

* Display the original and processed video sequences.

* Bring in experts to subjectively vote.

Complexity arises as

* New Video Processing systems may need new equipment to playback the video sequences.

* The original and processed video sequences should be displayed in random orders.

* Expert viewers are expensive and do not produce repeatable results.

* Digital displays scale incoming video sequences based on their native resolution.

* Display manufactures want to check resolutions at 2x the video rate.

Previous Options

Each vendor builds unique test equipment to verify their new algorithms. So the first job is to debug the test equipment before it can be used to verify a new design. Debugging the test equipment can take as long if not longer than debugging the display equipment.

Easier Solution

To streamline the process, equipment for video quality testing needs to be defined, which can capture, play, and analyze any two video sequences. Further, as new input/output modules are continuously under development, the test equipment should use an open-architecture approach to ease upgradeability.

Video Clarity defined the ClearView product line with these objectives in mind.

* Capture video sequences in as many formats as possible.

* Convert all video sequences to user-selectable resolution.

* Translate all video sequences to uncompressed Y'CbCr 4:2:2 or RGB 4:4:4.

* Support 8 and 10-bit data paths with upgradeability to future 12-bit modes.

* Store the video sequences as frames (fields) so that they can be played at any rate.

* Display the video sequences in real time in multiple viewing modes.

* VTR controls - play, shuttle, jog, pause

* Integer-based zoom & pan.

* Apply objective metrics to the video sequences.

* Export pieces of video sequences to further analyze off-line.

* Use a standard operating system so that the operator can run 3rd party analysis applications.

By working in the uncompressed domain, any two video processing algorithms can be compared independent of compression or other processing.

To further simplify the work flow, any video sequence can be played; while capturing another video sequence, thus, combining the video server and capture device into one unit. By doing this, the original source is already inside the test equipment so captured content alignment is easily obtained.

The operator chooses the output video resolution and output rate independent of the input. Video sequences are cropped or centered with black borders to meet the desired resolution, and then played-out at rates up to 120Hz. The video sequence is sent to the display adapter or panel to test desired resolutions and frame rates.

Further the operator can play any stored video sequence, at any speed, for any duration either manually or using automated play lists.

The original and processed video sequences can be displayed - side-by-side, mirrored, or seamless split - on a single display. This eliminates the need to calibrate two separate displays.

ClearView applies various objective metrics to the video sequences, generates graphs, and calculates an objective score.

While development of additional objective algorithms is ongoing, we have built a hybrid system that takes into consideration subjective testing with objective measurements. ClearView can easily be programmed to display video sequences for the expert viewers; while recording the objective metric scores along with the MOS. While the MOS cannot be repeated, the objective metric can, easily and readily.

Since the system is based on an open, Windows-based architecture, any objective measurement algorithm can be modeled off-line using the stored video sequences.

Benefits

* Repeatable tests, quantitative results, and a streamlined setup.

* Analyze 2 video sequences in real-time up to 1080P.

* Input virtually any file type or capture from any digital or analog source.

* Multiple viewing modes are presented on a single display - no need to calibrate 2 separate Television displays to compare video sequences.

* Integrated uncompressed, high definition Video Server and Capture Device.

* Ability to Play 2 fully uncompressed, HD Streams in Real-Time.

* Hybrid Solution with Integrated Objective Metrics and Subjective Viewing Modes.

Case Examples

In all of the following examples, the tests can be performed using software mockups of the actual hardware unit. ClearView exports video sequences as files and accepts video files as inputs.

A Video Processing manufacturer needs to

* Source for their video processing or encoders in SDI, Component, or DVI.

* Capture the output of their unit.

* Capture the output of their unit after it has been decoded.

* Visually inspect the new algorithm compared to the original and/or previous algorithms.

* Generate a Score for repeatability.

A VOD Server manufacture needs to

* A way to bring in multiple file formats into their system through SDI or Component.

* Visually inspect the output of their VOD server compared to the original Source.

* Generate a Score for repeatability.

A Set-top Box (STB) or Decoder manufacture needs to

* Capture a "Golden" video stream or the results of one of their competitors.

* Capture the output of their unit.

* Visually inspect the "Golden" stream compared to their decoded stream.

* Generate a Score for pass/fail.

A Graphic or Display chip manufacture needs to

* Play out "Source" video sequences at various resolutions and rates to their graphic or display chip through DVI, HDMI, or VGA.

* Capture the output of their unit.

* Visually inspect the output of their algorithm compared to the original Source.

* Generate a Score for repeatability.

A Display manufacture needs to

* Play out "Source" video sequences at various resolutions and rates to test their display through DVI, HDMI, or VGA.

* Visually inspect the performance of their Display.

* Generate a count of dropped frames if any occurred.

Summary

ClearView takes advantage of the high-reliability of today's off-the-shelf computer platforms. This ensures that products are made with state-of-the-art hardware, while at the same time avoiding the high cost of custom designs.

ClearView provides broadcasters, video researchers, compression developers with the unique ability to capture, play-out, and analyze video sequences. Objective measurements are generated and logged for repeatable tests.

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About Author

Both Trenton Moss & Bill Reckwerdt are contributors for EditorialToday. The above articles have been edited for relevancy and timeliness. All write-ups, reviews, tips and guides published by EditorialToday.com and its partners or affiliates are for informational purposes only. They should not be used for any legal or any other type of advice. We do not endorse any author, contributor, writer or article posted by our team.

Trenton Moss has sinced written about articles on various topics from Computers and The Internet, Legal Matters and Computers and The Internet. . Trenton Moss's top article generates over 18100 views. to your Favourites.

Bill Reckwerdt has sinced written about articles on various topics from Computers and The Internet, Satellite and Mortgage. Bill Reckwerdt, Vice President Marketing & Business DevelopmentBill's extensive career spans 20 years in the digital video industries. He brings to Video Clarity expertise in compression, digital transmission, and video servers.To contact Bill directly se. Bill Reckwerdt's top article generates over 1300 views. to your Favourites.

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