Media Compression - Scalable Continuous Media Streaming Systems - page 38

2.5.4.1 PSNR Performance

Figure 2.10 compares the PSNR performance (in terms of PSNR versus output bit-rate) of
the integrated transcoder with requantization and spatial downscaling. The PSNR of the video
segments generated with integrated transcoding at bit-rates below RTB and above RTB is
essentially identical to that obtained by spatial downscaling and requantization individually.
The results confirm that the integrated transcoder can always generate video with PSNR higher
than or equal to that obtained from using either requantization or spatial downscaling alone.

45

Requantization

40

Spatial Downscaling

Integrated Transcoding

35

RTB

30

25

20

0 200 400 600 800 1000 1200

Bit-rate (kbps)

(a) Education video clip

50

Requantization
Spatial Downscaling
Integrated Transcoding

45

40

35

RTB

30

25

20

0 200 400 600 800 1000 1200

Bit-rate (kbps)

(b) Onthestrip video clip

Figure 2.10 PSNR versus transcoded bit-rate