ETV Cookbook: Recipes: ATVEF

A high level of interactivity can be achieved by using the ATVEF specification to create synchronous enhancements. These enhancements appear to the viewer at a specific time and can contain material contextually related to specific points in the program.

ATVEF Transport A (ATVEF-A) delivers content triggers via the Line 21 closed caption channel and delivers content via the Internet.

Click Image for More Examples

SERVES

WebTV Plus Subscribers (Cable or Analog Broadcast)

AOL TV Subscribers (Cable or Analog Broadcast)

Ultimate TV Subscribers with WebTV Option (DirecTV Only)

ATVEF-Enabled Advanced Digital Cable Boxes

INGREDIENTS

HTML and/or TV Designers
It helps to have designers familiar with interactivity as well as those accustomed to graphic design for television.

ATVEF-Enabled Character Generator - Optional
Such a device creates HTML code and associated triggers using traditional broadcast graphics methods, especially useful for live applications.

Chyron Lyric

ATVEF Trigger Generator
(Not needed if ATVEF Character Generator above is used.)

CCaption - includes packaged software encoder.
EEG iTV XPress
Evertz ProCAP

Line 21 Encoder

CCaption - Creates ATVEF triggers and inserts them using a NLE or directly into a DV file.
Norpak
Evertz
EEG

Targeted Set Top Box and Subscription

AOLTV
MSN TV (formerly WebTV Plus)
UltimateTV

INSTRUCTIONS

Assess Deployment Options
One of the advantages of an ATVEF-A is that there are a variety of platforms being deployed. ATVEF-A can be received by advanced cable set top boxes currently in trials by several MSOs as well as the AOLTV, WebTV Plus, and UltimateTV consumer-purchased set top boxes. See Consumer vs. Cable Boxes for ATVEF

Learn About ATVEF-A Triggers
Triggers to activate content arrive via text channel 2 of line 21 and when first received activate an icon on the screen prompting the user to accept subsequent enhancements.

Every trigger begins with: <URL> A new URL activates a new page. A repeat URL activates a script.

Three optional elements follow:
[name:string] - For user's benefit when initiating enhancement.
[expires:datetime] - Makes enhancement expire at a given time.
[script:string] - Passes script fragment to receiver object in current page.

Two required elements complete the trigger:
[tve:1.0]
[checksum] - for checking trigger corruption in receiver

Learn About ATVEF-A Content
Content Level 1.0 requires support for HTML 4.0, CSS 1, JavaScript 1.1. Receivers are required to provide 1MB for content cache and 1KB for session cookies. Six MIME types must be supported: text/html (HTML 4.0), text/plain, text/css (CSS1 only), image/png, image/jpg (no progressive encoding) and audio/basic. Note that common plug-in support is not required and cannot be download by the user to a set-top-box.

The "TV:" URL references the television channel and may be used anywhere that a URL may reference an image, as in these examples:
<object data="tv:" width="60%" height="60%">
<img src="tv:" width=320 height=240>
<td width=320 height=240 style="background: url(tv:)">
<body style="background: url(tv:)">
<frameset style="background: url(tv:)" cols="200,*">
<a href="tv:">Click here to return to TV</a>

A trigger receiver object can be included to receive timed events, as in this example:
<OBJECT TYPE="application/tve-trigger" ID="triggerReceiverObj">

See this resource for more detail:

ATVEF Specification

Compare Target Platform to the ATVEF Specification
Some receivers claiming ATVEF compliance do not support all features of HTML 4.0. Also, differences in interpretation of the ATVEF and HTML standards exist. (For example, frame support is inconsistent.) Be aware of all platforms that might receive your content, and it's affect on them. You may need to consider providing a "browser sniffer" in your content to detect the type of platform and modify your content appropriately.

On the bright side, many platforms have support for Flash and larger cache sizes exceeding the ATVEF specification. See the ATVEF Platform Comparison.

Be Aware That It's Not the Web
In addition to the content restriction discussed above, review TV Authoring Guidelines. for specific television graphic restrictions. Also, be aware how long it will take content to reach the user given the rendering speed of the given platform and the particular way in which the content is delivered. Viewers expect a "television like" experience when using enhancements and may not accept slow page rendering considered acceptable on the web. This problem can be compounded if your web server isn't powerful enough, as a given television show might prompt thousands of users to click on the same content simultaneously.

Develop Enhancement Concepts
If at all possible, in meeting with producers, agree in the early stages of production the kinds of enhancements to be developed. Also, determine the specific times for them, as it can be difficult to find good locations for enhancements in a fast paced program. Frequently, time constraints will make it necessary for producers to cut sections of programs that provide deeper background on a topic being discussed. This is prime territory for an enhancement.

It should be noted that ATVEF-A does not necessarily have to be deployed in a synchronous manner. Some programs lend themselves to a single multifaceted enhancement that the user can browse at any point within the program.

Assemble Necessary Software and Hardware
At every stage of conception, it is important to test the ideas on the actual station and user equipment. You'll need the equipment ready to do this early in the design process.

Develop Enhancement Content
With a team of graphic designers, interactive developers, and either coders or character generator experts, develop the control structure, artistic look and editorial text for the enhancements. Immediately begin testing with users and producers using the emulator and target platform.

Test on Software Emulator and Refine
Most hardware vendors provide a software tool to emulate (not duplicate) the behavior of the hardware on a computer. This allows you to test content without needing to generate and insert triggers while connected to the set-top-box. However, some emulators do not allow you to see the enhancements in context of associated video or the triggers. Also, you will likely see the enhancements load much faster than user's with analog phone modems typical for these platforms.

Test on Hardware and Refine
Once your enhancements are stable on the emulator, you must test them on the actual set-top-box. Emulators can not be trusted to work exactly like the target platform.

Analog platforms can be connected directly to the trigger insertion equipment or a video tape for testing. Methods for testing UltimateTV and Digital cable set top boxes are uncertain.

Master the Program
Insure that the final version is present as needed on the appropriate web server before the broadcast. Using either offline or live tools, insert desired triggers at the appropriate times. Broadcast the show live or capture it to tape with triggers inserted. See the NewsHour WebTV Enhancement Guide for an example of a weekly production process.

Keep Content Available
Recognize that ATVEF-A content can be recorded for playback with enhancements many months later. Be sure to keep the web-server enhancement content and directory structure intact.

DIAGRAM