View source for Working (and Playing!) with REXX and OS/2 Multimedia

By [[Timothy F. Sipples]]

This are the notes of a presentation gave by [[Timothy F. Sipples]] on 15 May 1994 on the Fifth Annual REXX Symposium. 


==What is Multimedia?==

* Combining still images (bitmaps), animation, software motion video, text, and/or audio to present information
* Principle technologies: CD-ROM, laserdisc, digital audio, MIDI, high resolution displays with more colors
* Principle file formats: WAV, MID, and AVI
* Multimedia NOT invented by Comptons

...We like to call it ULTIMEDIA

==Why use Multimedia?==

* "It's the market, stupid."
* Triggers: to "describe" events
* Education/training
* Kiosks (point-of-sale)
* Presentations and demos
* Better human interfaces generally
* Entertainment and games

==Requirements for OS/2 Multimedia==

* OS/2 2.1 with Multimedia Presentation Manager/2 (included)
* Standard OS/2 hardware requirements
* Some additional RAM (to 12 MB) recommended
* CD-ROM drive
* Audio adapter (Creative Labs, MediaVision, IBM, etc.)
* Display with at least 256 colors recommended
* Video capture adapter (optional)
* Laserdisc player with computer control (optional)

==Major Features in MMPM/2 1.1==

* Multimedia folder
* Sound setup object (for system sounds)
* Applets
* Volume control
* Drivers
* Sample files
* Lotus 1-2-3 and Excel audio macros
* External function library for REXX and help file

==Principle File Formats==

* Generally a superset of Windows file formats
* WAV: Digital audio (pulse code modulation, and variants)
* MID: Standard MIDI file format (for instrumental music)
* AVI: Audio-video interleaved (IBM Ultimotion and Intel Indeo)
* Conversion applet for some additional file formats included (AVC, VOC, DIB, DMP, ADPCM, M-Motion)
* High degree of modularity permits addition of more file formats (e.g. FLI/FLC)

==Principle REXX Features==

* Multimedia with REXX help file
* PLAY.CMD
* RECORD.CMD
* Entire MCI (media control interface) command set available, not just subset described in online help
* External function library (MCIAPI.DLL) provides access to MCI command set

==Key Limitations==

* REXX is unable to deal with loss of device (meaning ACQUIRE EXCLUSIVE must be used)
* REXX program should not hold device exclusive for long
* Unless using PMREXX (or one of the visual REXX builders), MCI commands which require Presentation Manager (such as Ultimotion playback) will fail
* REXX does not receive PM messages (to easily monitor the status of playback and devices)
* MCI's implicit opens are assumed shareable (and not necessarily desired with REXX)

==Sample REXX Script==

 /* Load and initialize Multimedia REXX support */
 call RXFUNCADD 'mciRxInit','MCIAPI','mciRxInit'
 call mciRxInit 
 
 /* Open default digital audio device, exclusive use */
 rc = mciRxSendString('open waveaudio alias wave wait','RetStr','0','0') 
 
 /* Check error, call function to return error string */
 if rc <> 0 then
 do
 	MacRC = mciRxGetErrorString(rc,'ErrStVar')
 	say 'rc =' rc ', ErrStVar =' ErrStVar
 end
 
 /* Load a digital audio file */
 rc = mciRxSendString('load wave sample.wav wait','RetStr','0','0') 
 
 /* Obtain ID for device context that was just opened */
 DevID = mciRxGetDeviceID(wave) 
 
 say 'DevID =' DevID
 
 /* Set the time format to milliseconds */
 call mciRxSendString 'set wave time format ms','RetStr','0','0'
 
 /* Determine whether the microphone connection enable */
 call mciRxSendString 'connector wave query type microphone wait','RetStr','0','0'
 
 say 'connector query microphone:  RetStr =' RetStr
 
 /* Query length of the opened file, value in ms */
 call mciRxSendString 'status wave length wait','RetStr','0','0'
 
 say 'status wave length:  RetStr =' RetStr
 
 /* Play the multimedia file, wait for completion */
 call mciRxSendString 'play wave wait','RetStr','0','0'
 
 /* "Rewind" to the beginning of the file */
 call mciRxSendString 'seek wave to start wait','RetStr','0','0' 
 
 /* Close the device context */
 call mciRxSendString 'close wave','RetStr','0','0'
 
 /* Ensure proper termination of Multimedia REXX */
 call mciRxExit
 
 exit(0)

==Live Demos==

* PLAY.CMD
* FOR..DO
* Ultimotion
* RECORD.CMD
* Modifications to the sample .CMD files
* Dial 1.1 by Helge Hafting

==Links==
* [http://www.rexxla.org/rexxlang/mfc/rexxsr94.txt Aditional info about the event]

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