Affiliation 1) Eindhoven University of Technology Department of Mathematics and Computer Science

Affiliation1) Eindhoven University of Technology

Department of Mathematics and Computer Science

HG 6.57, P.O. Box 513, NL-5600 MB, Eindhoven, The Netherlands2) Philips Research NatLab

Prof. Holstlaan 4, 5656AA Eindhoven, The Netherlands

IFD – a technique for improving the quality of wireless video streaming

Author: S. Kozlov 1. Co-authors: Peter v.d. Stok 1,2, Johan Lukkien 1

Bandwidth variations

Sender’s buffer

2. MPEG over wireless link

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

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) -> low latency (80ms)• Tolerating bandwidth degradation of up to 50% of the video bit-rate

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

Frame inter-dependencies: losing a P frames (red cross) causes the dependent frames to be decoded incorrectly (grey crosses)

Packets get lost here

Quality degradation

C W S

incoming frame

waiting (buffered) frame

sent frame

WHILE (TRUE) DOWHILE (C is empty) DO NothingIF (W is empty) THEN Store C in WELSE

IF (C is of type I) THEN Overwrite W with CELSE IF (C is of type B) Discard CELSE IF (W is of type I or P) Discard CELSE Overwrite W with C

4. Testing and validation

I0B1B2P3B4B5P6B7B8(I9)

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

Video bit-rate: 4Mbps. Losing B frames mostly when the oven is on

Video bit-rate: 5Mbps. No I or P frames get lost Video bit-rate: 8Mbps. Also I and P frames get lost when the oven is on

Cumulative weight of B frames is more than 50%

Video: 4Mbps, bandwidth: 2.5Mbps Video: 4Mbps, bandwidth: 1.6Mbps

Losing an I or P frame:

size, kB

frame

40

20

B framesI frames P frames

Socket buffer

Physical and link layers (802.11)

Layers above link layer

Bandwidth variations may cause the buffer to overflow

Buffer occupancy: