25-05-2012, 04:15 PM
A Video Streaming System for Mobile Phones: Practice and Experience
[attachment=23043]
Introduction
As high-speed wireless network technologies such as GPRS
and CDMA2000 1X become a reality, cellular phone is expanding
its role to be a computing device, not just a voice
communication device, and people are exploring to run various
applications on cell phone [5]. However, the computing
environment of cellular phones is so different from the desktop
processors that direct porting of the desktop applications to
cellular phone often finishes as a failure. The difference exists
in all aspects—CPU speed, memory size, display dimension
and so on. And importantly, porting itself is technically a big
problem because few debugging tools are available; in other
words, the computing environment is similar to that of early
computing systems a couple decades ago.
Lightweight video player for mobile phone
This section discusses the lightweight video player we have
developed for use in mobile phone. The dithering issue and
the decoding process on mobile phone are also discussed.
Dithering on mobile phone
A common type of the off-the-shelf cell phones has a display
device with different number of colors; e.g., gray scale
LCDs, 256-color or 65536-color LCDs. The video decoder
running on cell phones should therefore perform dithering
for a better image quality. Dithering is a process of converting
24-bits device-independent images into appropriate image
formats suitable for LCD display. The dithering algorithm is
usually applied to a RGB image obtained from the up-sampled
YUV pixels as shown in figure 2(a). As dithering algorithms
usuallywork on the whole pixels on every frame, the computation
requirement is not trivial. Hence, it is necessary for a video
decoder to support the dithering mechanism at the decoding
level rather than at the rendering level as shown in figure 2(b).
Here, “decoding level” means that the output of the inverse
function of the wavelet transform becomes a dithered YUV
image.
Wireless streaming server
This section describes the server issues for the wireless streaming
system we have developed. The server architecture is described
first and the rate control policy used in our implementation
is then presented.
Conclusion
The mobile streaming system presented in this paper has actually
been implemented and commercially deployed nationalwide,
by one of the major wireless carriers, in the Republic of
Korea. The number of LVF-enabled cell phones deployed in
the country are currently more than a million and we expect
that the number will grow sharply. As there are several types
of cell phones supporting different color space, the contents
providers make their video clips (combined audio and caption)
in gray (4-level) or color (256, 4096, 65536 colors) formats and
upload them into the server. People can receive and play video
clips stored in the server via their LVF-enbled cell phones. A
typical video clip is about 150 KBytes long (approximately 30
seconds of playback duration) and it normally takes less than
30 seconds to receive the whole clip in CDMA2000 backbone.
The server has been implemented to support 1,000 concurrent
streams and thoroughly tested to meet this requirement.
[attachment=23043]
Introduction
As high-speed wireless network technologies such as GPRS
and CDMA2000 1X become a reality, cellular phone is expanding
its role to be a computing device, not just a voice
communication device, and people are exploring to run various
applications on cell phone [5]. However, the computing
environment of cellular phones is so different from the desktop
processors that direct porting of the desktop applications to
cellular phone often finishes as a failure. The difference exists
in all aspects—CPU speed, memory size, display dimension
and so on. And importantly, porting itself is technically a big
problem because few debugging tools are available; in other
words, the computing environment is similar to that of early
computing systems a couple decades ago.
Lightweight video player for mobile phone
This section discusses the lightweight video player we have
developed for use in mobile phone. The dithering issue and
the decoding process on mobile phone are also discussed.
Dithering on mobile phone
A common type of the off-the-shelf cell phones has a display
device with different number of colors; e.g., gray scale
LCDs, 256-color or 65536-color LCDs. The video decoder
running on cell phones should therefore perform dithering
for a better image quality. Dithering is a process of converting
24-bits device-independent images into appropriate image
formats suitable for LCD display. The dithering algorithm is
usually applied to a RGB image obtained from the up-sampled
YUV pixels as shown in figure 2(a). As dithering algorithms
usuallywork on the whole pixels on every frame, the computation
requirement is not trivial. Hence, it is necessary for a video
decoder to support the dithering mechanism at the decoding
level rather than at the rendering level as shown in figure 2(b).
Here, “decoding level” means that the output of the inverse
function of the wavelet transform becomes a dithered YUV
image.
Wireless streaming server
This section describes the server issues for the wireless streaming
system we have developed. The server architecture is described
first and the rate control policy used in our implementation
is then presented.
Conclusion
The mobile streaming system presented in this paper has actually
been implemented and commercially deployed nationalwide,
by one of the major wireless carriers, in the Republic of
Korea. The number of LVF-enabled cell phones deployed in
the country are currently more than a million and we expect
that the number will grow sharply. As there are several types
of cell phones supporting different color space, the contents
providers make their video clips (combined audio and caption)
in gray (4-level) or color (256, 4096, 65536 colors) formats and
upload them into the server. People can receive and play video
clips stored in the server via their LVF-enbled cell phones. A
typical video clip is about 150 KBytes long (approximately 30
seconds of playback duration) and it normally takes less than
30 seconds to receive the whole clip in CDMA2000 backbone.
The server has been implemented to support 1,000 concurrent
streams and thoroughly tested to meet this requirement.