Developing a Java API for Digital Video control using the Firewire SDK

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Developing a Java API for Digital Video control
using the Firewire SDK
Academic Developers Conference 2001

• Damon Woolley
• Bing-Chang Lai
• Phillip John McKerrow
• University of Wollongong

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Introduction

• What is Firewire?
• The API
• Version in Paper
• Current Version
• Using the API
• To do list
• Where to get the API
• QA

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What is Firewire?

• Firewire is Apples name for IEEE 1394 Standard
• High-speed bus (Up to 400 Mbits per second)
• Hot-swappable
• Easy cabling

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What is Firewire?

• Different data can be sent across Firewire of
  which Digital Video (DV) is one.
• Digital Video (DV)
• Uses compression similar to motion-JPEG
• Compression rate of around 51
• Constant data rate of 36 Mbits per second

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What is Firewire?

• Firewire provides a standard for interacting with
  DV devices
• Called Audio Video/Control (AV/C)
• The Java API being developed by UOW is for
  providing an easy-to-use interface to AV/C

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The API

• Easy-to-use Java interface to AV/C
• Original Firewire AV/C commands are all in
  low-level C

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The API

• The API has the following structure
• Java Application
• JNI Layer
• C/C Layer
• Firewire
• Version in Paper
• Used a C Layer, adapted from IsochComponent from
  the Firewire SDK
• Current Version
• Uses a C layer, and mirrors the C API to Java
• Only supports MacOS X

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Version in Paper

• Adapted from IsochTest Example provided with
  Firewire SDK
• A prototype for learning
• Extract the appropriate functions
• Expose these C functions to Java
• Therefore it does not have a very correct
  structure or design

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Version in Paper

• Software Architecture (From Paper)

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Version in Paper

• JNIOut
• void InitDV(String msg)
• Print Information about available components
• void OpenDV(String msg)
• Gets the default dv component
• Print information about the component
• Sets the video configuration of the component
• void OpenControlDV(String msg)
• Open device for reading
• void CloseControlDV()
• Close device

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Version in Paper

• JNIOut
• void ControlDV(int op1, int op2)
• Uses op1 and op2 to create an AV/C command, and
  sends it to the DV device
• Some opcodes are listed in the paper
• Complete opcodes are available from
  http//www.1394ta.org/Technology/Specifications/
  Descriptions/1394_AVC.htm
• eg. Play (0xc3, 0x75), Stop (0xc4, 0x60), Fast
  Forward (0xc4, 0x75), Rewind (0xc4, 0x65)

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Current Version

• DVController
• Uses JNIOut. Calls ControlDV and passes AV/C
  operand codes

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Current Version

• In avc namespace, avc package
• AVDeviceFactory
• AVDevice getDefaultDevice()
• Creates an AVDevice from the default dv component
• The device is initialised when AVDevice is
  constructed
• Corresponds to OpenDV
• AVDevice
• boolean open()
• opens the device
• Corresponds to OpenControlDV

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Current Version

• AVDevice
• boolean close()
• closes the device
• Corresponds to CloseControlDV
• boolean play()
• boolean stop()
• boolean fastforward()
• boolean rewind()
• boolean nextframe()
• boolean prevframe()

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Current Version

• AVDevice
• boolean slowplay()
• boolean fastplay()
• boolean rplay()

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Using the API
Version in Paper System.loadLibrary("JNIOut") ...
JNIOut interface new JNIOut() interface.InitDV
() interface.OpenDV() interface.OpenControlDV()
... // Play Command interface.ControlDV(0xc3,
0x75) ... // Stop Command interface.ControlDV(0xc
4, 0x60) ... interface.CloseControlDV()
Current Version System.loadLibrary("AVC") ... AVD
eviceFactory f new AVDeviceFactory() AVDevice
d f.getDefaultDevice() d.open() // Will
return false if failed ... d.play() // Will
return false if failed ... d.stop() // Will
return false if failed ... d.close()
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To-Do List

• Provide ControlDV equivalent
• Provide more functions
• Time Code Functions
• Get Time Code
• Go to a specific Time Code
• Instead of returning True/False, functions will
  throw Exceptions

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Where to get the API

• Planning on putting the current version onto
  www.kagi.com for about AU10 a copy, probably
  with source
• Not done yet
• If you want to know when it will be up, you can
  email me on bl12_at_uow.edu.au

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References

• D. Woolley, B. Lai, P.J. McKerrow, Developing a
  Java API for Digital Video Control using the
  Firewire SDK, AUC 2001
• 1394 Trade Association, AV/C Digital Interface
  Command Set, Version 1, Sept 1996, see
  http//www.1394ta.org/Technology/Specifications/
  Descriptions/1394_AVC.htm
• Apple Inc., Firewire SDK 9 for MacOS X, see
  http//developer.apple.com/hardware/FireWire/

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QA