Affiliation

1
IFD a technique for improving the quality of
wireless video streamingAuthor S. Kozlov 1.
Co-authors Peter v.d. Stok 1,2, Johan Lukkien 1

1. Introduction A crucial point in using
wireless networks for multimedia tasks is the
effective use of highly fluctuating network
resources. Using the sender buffer as instant
indicator of the varying network state, we
implement a simple yet effective technique to
greatly improve the quality of video streaming
over wireless link.
3. IFD (I Frame Delay) scheduler
waiting (buffered) frame
sent frame
incoming frame
C
W
S
WHILE (TRUE) DO WHILE (C is empty) DO
Nothing IF (W is empty) THEN Store C in
W ELSE IF (C is of type I) THEN Overwrite W
with C ELSE IF (C is of type B) Discard
C ELSE IF (W is of type I or P) Discard
C ELSE Overwrite W with C
2. MPEG over wireless link
Bandwidth variations
Buffer occupancy

• Link 802.11b
• UDP effective throughput
• Discretisation time 40ms
• Microwave oven on between 5 and 13 seconds

Video 4Mbps, bandwidth 1.6Mbps
Video 4Mbps, bandwidth 2.5Mbps
Senders buffer
4. Testing and validation
Physical and link layers (802.11)
Layers above link layer
Packets get lost here

• Stream 1min, 25fps, 3 various bit-rates
• Link 802.11b
• Microwave oven on between 20s and 40s

Socket buffer
Bandwidth variations may cause the buffer to
overflow
Video bit-rate 4Mbps. Losing B frames mostly
when the oven is on
Quality degradation
Frame inter-dependencies losing a P frames (red
cross) causes the dependent frames to be decoded
incorrectly (grey crosses)
Video bit-rate 8Mbps. Also I and P frames get
lost when the oven is on
Video bit-rate 5Mbps. No I or P frames get lost
Losing an I or P frame

• 5. Conclusions
• Simple (only the sender should be changed)
• Cost effective (small buffers needed)
• Works with any terminals supporting RTP
  reception and equipped with a general MPEG
  decoder
• Very reactive against fast network fluctuations
• Very small buffer (2 frames) -gt low latency
  (80ms)
• Tolerating bandwidth degradation of up to 50 of
  the video bit-rate

Cumulative weight of B frames is more than 50

• Affiliation
• 1) Eindhoven University of Technology
• Department of Mathematics and Computer Science
• HG 6.57, P.O. Box 513, NL-5600 MB, Eindhoven, The
  Netherlands
• 2) Philips Research NatLab
• Prof. Holstlaan 4, 5656AA Eindhoven, The
  Netherlands