Media Compression - Scalable Continuous Media Streaming Systems - page 28

High-Definition Video:
Resolutions up to 1920 × 1080 pixels
30 fps
24 bits per pixel
Raw data rate

=

1.5 Gbps.
Emerging Ultra-High-Definition Video:
4 times the resolution (and data rate) of HDTV.

2.1.3 Media Compression
From the previous discussions we can clearly observe that the raw data rates generated by high-
resolution audio and video are extremely high, even compared to today's broadband network
technologies. Therefore, it is essential to apply compression to the media data to reduce the
storage and bandwidth requirements to economical levels. Many extremely successful media
compression standards have been developed over the years and some of them are summarized
below:

MPEG-1 [6-10]:
VCR-quality video up to 8 Mbps
Used in video-CD, CD-I and video-on-demand systems.
MPEG-2 [11-19]:
Broadcast quality video from 3 to > 10 Mbps
Used in DVD, HDTV, and video-on-demand systems.
MPEG-3:
Originally slated for HDTV but later dropped due to the incorporation of HDTV into
MPEG-2.
MPEG-4 [20-35]:
Originally targeted at low-bit-rate video for video telephony systems.
Now expanded to a broad range of bit-rates up to high-definition video.
The advanced video coding standard in Part 10 [29] of the MPEG-4 standard is also known
as H.264. This advanced codec can achieve even greater compression ratio using more
sophisticated compression algorithms.

For audio and video compression a vast body of work has been conducted in the past several
decades and there are also many excellent texts and chapters available in the literature [1-5].
Thus, instead of repeating materials available elsewhere, we will focus on the impact of media
compression on media streaming.

2.2 Media Multiplexing
Figure 2.3 depicts the typical structure of an MPEG encoder. The encoder in fact comprises
two independent encoders, one for audio stream and one for video stream. These two media
streams are first encoded independently to produce the corresponding compressed audio and
compressed video streams, and then multiplexed together by the system encoder to a system
stream. The multiplexer serves the important function of adding presentation time stamps to the