Media Compression - Scalable Continuous Media Streaming Systems - page 39

2.5.4.2 Bit-rate Conformance

Bit-rate conformance, defined as the ratio between the output bit-rate and the target bit-rate,
measures how well a transcoder can control the transcoding process to achieve the desired
output bit-rate.
Figure 2.11 plots the bit-rate conformance versus target bit-rate ranging from 100 kbps to
1.1 Mbps. The results show that requantization cannot adapt to the lower bit-rates (e.g., below

1.2

Requantization
Spatial Downscaling
Integrated Transcoding

1.15

1.1

1.05

1

0.95

0.9

100 200 300 400 500 600 700 800 900 1000 1100

Target bit-rate (kbps)

(a) Education video clip

1.2

Requantization
Spatial Downscaling
Integrated Transcoding

1.15

1.1

1.05

1

0.95

0.9

1000

100 200 300 400 500 600 700 800 900 1100

Target bit-rate (kbps)

(b) Onthestrip video clip

Figure 2.11 Bit-rate conformance versus target bit-rate