Getting to Know TiVo: The Home Media Engine (HME SDK)Eric M. UpchurchCS 525Spring 2008

Introduction• TiVo is a popular set-top DVR that can be

connected to a home network• Through the network connection, the TiVo can

access applications through a special transport protocol (the HME protocol)

• The HME SDK facilitates development of applications that utilize the HME protocol▫ Photo viewers▫ Music players▫ RSS feeds▫ Streaming radio▫ Games▫ etc

Motivation• Interested in developing TiVo apps prior to

CS525▫Also seemed a perfect fit for the class

•Relatively new to TiVo, and wanted to play around with it

•Have run several third-party applications•Curious what the capabilities of the SDK are•Could not find exactly what I was looking for

▫A photo slideshow with music

The HME Protocol• HME applications use a client/server architecture

▫Server is a PC or possibly a server on the Internet▫Client is the TiVo receiver

• Protocol uses a single bi-directional TCP/IP socket• Language independent

▫Applications just have to communicate with TiVo via the protocol, and so could be developed in any language

• Uses chunked data encoding (1-65K byte chunks)▫Allows arbitrary data size by spanning chunks▫Enables reader of a stream to skip to next chunk if

an error occurs

HME Architecture

HME SDK• A complete API and developer kit for

creating HME applications in Java• Wraps the HME protocol into an event-driven

architecture ▫More or less MVC, similar to Java Swing

• TiVo boxes find HME applications using Multicast DNS (mDNS/Zeroconf) and DNS Service Discovery (DNS-SD)▫“Bonjour”, developed by Apple Computer▫No network setup required▫Don’t need to know IP addresses, host names,

or ports

HME SDK Class Structure• Applications inherit from the Application class• GUI is composed of Views containing Resources

▫ View instances contain a single resource, and provide a coordinate system and transparency

▫ Resources are (mostly) visual elements: fonts, colors, images, text, and animations. Also sounds, music (streamed)

▫ Views are laid out to draw a screen on the TiVo receiver’s display

HME Application Structure• An application is composed of a view hierarchy

▫ Root view covers entire display▫ Views can have child views, which cover some

portion of the screen relative to the parent• Views may be invisible or zero size to

accommodate non-visual elements, such as sounds

• Views can have streaming image or music (MP3) resources▫ Events notify the application as the stream is read

• Animation resources provide visual effects (e.g. fade-in/out)▫ Useful for hiding network latency

• Views and resources handle events sent by TiVo

Bananas UI Toolkit• TiVo toolkit for building TiVo user interfaces• Extends the basic HME SDK• Provides an application framework

▫Applications are composed of a stack of screens

▫Provides focus management between widgets• Provides a standard widget set

▫Button▫Text▫List▫Keyboard

• Provides a standardized look and feel▫Similar to the base TiVo UI

HME Hosting Environment• Uses factory pattern to serve up applications

▫ Each available application has a factory class that provides instances of the app to a TiVo receiver

▫ New instances are created when a connection is established from a TiVo receiver

• Single hosting environment (one JVM) can serve multiple application types

• Applications are accessed via an HTTP URL request from the receiver▫ Example: http://myPC:7788/MyTiVoApp▫ Hosting environment maps the URL to an application

factory by name (e.g. MyTiVoAppFactory)• Custom hosting environments can be created for

extensibility to server domain

HME Hosting Environment

HME Simulator• The HME SDK includes a TiVo simulator for

testing▫Greatly facilitates rapid application development

• Works like the TiVo receiver• Allows you to see the view hierarchy and

memory usage of application• Provides debugging options• Overlays “safe” television area bounding boxes

▫This shows the area that is safe on all televisions, including those that overscan

• Not a substitute for testing on a TiVo receiver▫Response speed is vastly different▫Network latency may be different

Conclusions

•TiVo HME is a powerful SDK for developing applications for display on TiVo

•Bananas UI toolkit eases construction of professional looking application

•A couple of shortcomings:▫An HD capable alpha version has been

released, but I could not get it to work. Stuck with SD (640x480) for now.

▫Does not allow streaming of video content!

References & Resources• TiVo HME Software Developer Kit Developer's Guide

Release 1.4. http://tivohme.sourceforge.net/docs/hmesdk/hme-devguideTOC.html

• TiVo Bananas UI Toolkit Developer’s Guide Release 1.3. http://tivohme.sourceforge.net/docs/bananas/bananas-devguideTOC.html

• TiVo Home Media Engine (HME) SDK Info. http://bitrazor.com/content/tivo/hme/index.php

• TiVo. Wikipedia. http://en.wikipedia.org/wiki/TiVo• Flash demo: Getting Started with Eclipse and the TiVo

HME SDK. http://bitrazor.com/content/tivo/hme/tivo_hme_eclipse_demo1.php

• TiVo Developer How-Tos. http://bitrazor.com/content/tivo/hme/howtos/index.php

Backup SlidesIn the event the demo doesn’t work

My HME Application – Intro Screen

• Currently one slideshow

• Extend to multiple XML defined slideshows, listed here

• Uses common TiVo look and feel

• User selects enter or right arrow button to start slideshow

My HME Application – Slideshow Screen

• Photos randomly change every N seconds

• Photos fade in/out

• Music tracks randomly selected

• User selects left arrow button to return to previous screen