Mobile Intelligence

23.5 SUMMARY

The ubiquitous computing environment has strict constraints on the resources, such as processing time and battery life. How to minimize energy consumption while ensuring a desirable level of video quality becomes a challenge. In this chapter, we encode films by several popular codecs nowadays and measure the electric energy consumption of them to find out which video codec is most suitable for mobile handheld devices.

Constraints of resources of the ubiquitous computing environment call for wise strategy for energy consumption management. Codecs and their encoding parameters have effects on energy consumptions when replaying or decoding video code encoded by them. We summarize their influences as follows.

• Type of codecs: From experimental results, we find that when playing films encoded by one group of codecs, including XviD, DivX3, DivX5, and H.263+, less electricity is consumed than playing films encoded by the other group of codecs, including MS MPEG-4, WMV2, and WMV3. When watching films encoded by all kinds of popular codecs on small screens of handheld devices, the picture quality are found to be nearly the same. The mobile handheld device users are recommended to encode films by the group of codecs consuming less electricity.
• Video file format: In view of the file formats, experiments show that as long as the same codec is used, it makes not much difference as what file format is chosen.
• Encoding parameters: To have better picture quality, we can encode video ...