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1、semiconductor solutionsDesign tip: Improve Audio Experience in Linux-Based NetbooksDescriptionThe main operating systems (OS) used in netbooks are Windows XP and Linux-based OS. These operating systems work best with the low-power CPUs in todays netbooks, which are mostly running Intel Atom processo
2、rs, and offer the best fit for the system requirements, specifications and configuration of netbooks. Linux enables a lower-cost solution for netbook designers as its royalties are lower, helping keep the price point low. Linux also uses less system memory, which is required for higher performance,
3、and is generally much faster than Windows.Although Linux may be a perfect fit with regards to many functions of a netbook, it does not provide dynamic audio. Windows quickly became the dominant PC operating system, meaning that since Linux wasnt in high demand for PCs, the audio capabilities of Linu
4、x became an afterthought and software enhancements were not readily available.As Linux does not have built-in high-quality audio capabilities, a software driver with optional advanced technologies must be added to devices running Linux. The driver needs to feature a system wide equalizer, a compress
5、or/limiter, acoustic echo cancellation and noise suppression. These features will help offset the low-quality speakers that are generally used in these small form factor devices, which is necessary to maintain a reasonable price point.Small form factor netbooks with low-quality speakers generally pr
6、oduce poor sound or frequency responses from music. To compensate for this problem, an equalizer can set and adjust various bands, filters and frequency widths to create a system wide parametric equalizer, or multi-band equalizer that contours the sound on the PC to improve the audio fidelity and li
7、stening experience. The amplitude of each band can be tuned with the shifting and widening or narrowing of the center frequency.In addition to music, low-quality speakers and poor audio sub-system design in netbooks will also be noticeable when watching a video or movie. For example, when listening
8、to a conversation during a battle scene in a war movie, typically the speech between two characters is not as clear or loud because of background war noise. This results in a poor user experience, since quiet conversation or media can be difficult to hear while loud voices can become much distorted
9、and might even damage the small, space-constrained speakers. To help with this, an audio compressor and limiter feature allows the system builder to make the system as loud as possible without distorting and damaging the low-cost speakers of the unit. It does this with real-time precision and can ma
10、ke the system more than 5 decibels (dB) louder without turning up the internal amplifier.A compressor basically reduces the dynamic range of an audio signal into a smaller dynamic range. In the movie example, it reduces the level of the loud explosions, but not the gentle sounds of the conversation
11、between two characters. Thus, the level can be raised where the conversation can be heard without the loud sounds being too loud. This is also very similar to an automatic volume control in an automobile.1IDT Design tip: ImPrOvE AUDIO EXPErIENCE IN LINUX-BASED NETBOOkS 2009 Integrated Device Technol
12、ogy, Inc. All rights reserved. Product specifications subject to change without notice. IDT and the IDT logo are registered trademarks of Integrated Device Technology, Inc. All other brands, product names and marks are or may be trademarks or registered trademarks used to identify products or servic
13、es of their respective owners. Printed in USA 12-09/JR/LMN/PDF_r1v1 TIP-PCaudio-129Discover what IDT know-how can do for you. www.IDT.com/go/PCaudioA limiter or “limiting” is similar to compression, but is used to make sure that the audio signal does not go above a specified level. This is extremely
14、 helpful to prevent the low-quality speakers and amplifiers from overloading or even being destroyed by excessive power peaks and ensures that users dont experience distortion. When purchasing a netbook from a retailer, the consumer should look for words like “speaker protection” or “audio normaliza
15、tion.” These are two common names for a limiter. The compressor and limiter will come pre-installed on the system and will protect the complete audio system.Another main feature of the netbook is wireless LAN for Internet connectivity. many people are using netbooks as an Instant messaging (Im) and video portal to stay in touch with friends and family. However, with noisy environment and feedback from the internal speakers and microphones, the voice over Internet Protocol (voIP) or chat experience is not pleasant because the sound from t
