Dynamic Bit Allocation for Video Conferencing

Midterm Report

Benjamin Pugliese <pugliese@andrew.cmu.edu>
Matthew Richey <mr6v@andrew.cmu.edu>
Mahesh Saptharishi <mahesh@andrew.cmu.edu>

Midterm Goals:

• Writing the necessary code for accessing video and audio hardware.
• Integrating the provided video codec.
• Writing a basic audio codec and networking layer.
• Demonstrating basic videoconferencing with two computers.

Accomplishments:

• Frame grabbing accomplished using Video for Windows.
• Raw audio inputted and outputted to sound card.
• Datagram socket interface written.
• H.263v2 encoder modified to take real-time video input.
• ADPCM audio compression implemented (4:1 compression ratio).
• Raw video remotely displayed.

Shortcomings:

• H.263v2 decoder not working with real-time input.
• Audio software only works on certain computers.
• System not completely integrated.
• System is not stable.

Conclusions:

Writing software interfaces to hardware took much longer than expected. A connectionless protocol for our data transmission (UDP) demonstrated better performance than a connection-oriented protocol (TCP). Our ADPCM code provided a constant bit rate, which does not lend itself to our dynamic bit allocation scheme (we would like to adjust audio parameters dynamically).

Future Plans:

• Fix the H.263v2 decoder so that it decodes in real-time.
• Develop a simple audio codec with adjustable parameters.
• Fully integrate the video conferencing system.
• Develop a scheme to implement dynamic bit allocation.

Code:

Find a compressed copy of our code here. All code was developed using Microsoft Visual C++ 6.0. Note: A few bugs still exist in this version and are being fixed.