Virtual Network Computer Recorder A Tool for Remote Learning
Group Members Marc Alban Jason Bonta Matt Jonker Greg Ose John Ruble Ashish Samuel
Overview Record all presentation material for distribution and review –Application / video display –Lecturer voice and audio Leverage existing technologies –VNC (Virtual Network Computer) –Audio compression (MP3 encoding/decoding)
Goals Seamlessly integrated and easy to use recording program Easy to distribute and efficiently sized session data file Portable client to playback recorded session
Existing Solutions vncrec –Unix command line –No audio vnc2swf –Separate audio recording –Exports to flash movie
Technical Implementation Microsoft C#.Net –Microsoft DirectX (DirectSound) Open Source Libraries –LAME –LibMAD –ZLIB Open Source RealVNC Server
Recorder Architecture Overview VNCR Recorder VNC Server VNC Client Audio Recorder Synchronizer MP3 Data Screen Updates Interleaved Audio/Video File
Video Recording / Playback Capture –Receives screen updates from RealVNC –Zip raw bitmap data –Add timestamps Playback –Get screen update from file –Unzip data and add to queue –Draw screen updates to screen buffer
Audio Recording / Playback Capture –Receive PCM data from DirectSound device buffer –Convert from PCM to MP3 using LAME Playback –Get chunk of MP3 data from file –Decode MP3 data using LibMAD –Put PCM data into DirectSound playback buffer
File Format Contains both audio and video data Synchronized using shared timestamps Video –Recorded from local VNC server –Lightweight screen encoding, uses GZIP compression Audio –Captured using DirectSound input device –Compressed using MP3 encoding Layered principle to promote modularity
File Format Diagram
Usage Examples Historical archive of lecture material Natural walkthrough and explanation of code Demonstration of the usage of any application Unlimited recording potential
Future Goals File editor Web browser plugin Streaming playback Fullscreen playback Integrated screen annotation
Example Demonstration Class lecture to teach basic networking