Janne Vainio

The effect of source based rate adaptation extension in AMR-WB speech codec

This paper presents a source based rate adaptation concept for AMR wideband speech codec. The source based rate adaptation algorithm selects the multi rate codec mode based on the input speech characteristics and coding parameters to minimise the average bit rate. The presented concept introduces up to 50% reduction in average bit rate without any degradation in speech quality. The benefit of source based adaptation is in increasing the system capacity in conversational services as well as storage size in messaging type of applications.

GSM EFR based multi-rate codec family

This paper describes a multi-rate codec family developed as a potential candidate for the GSM adaptive multi-rate (AMR) codec standard. The codec family consists of the GSM enhanced full rate (EFR) codec and lower bit-rate extensions thereof. The codec family consists of several codecs, i.e., modes that have different bit-rate partitionings between source coding and error protection. All the source codecs use the same ACELP-method (algebraic code excited linear predictive coding) used also in the GSM EFR codec. The codec operates at gross bit-rates of 22.8 kbit/s in the GSM full rate (FR) channel and 11.4 kbit/s in the GSM half rate (HR) channel. In the full rate channel, the codec provides improved error robustness over the GSM enhanced full rate (EFR) codec. It extends wireline quality (equal to or better than G.726-32 ADPCM) to poor channel error conditions with low C/I-ratios of 7 dB or even below. When operated in the half rate channel, the codec provides improved channel capacity while still providing wireline quality at high C/I-ratios above 16-19 dB.

Interacting with the flow

Mobile devices offer challenges for UI design. Limited screen space leads to deep menus, complex navigation and loss of position. We introduce a new user interface concept that reverses the traditional navigation paradigm. By utilizing context awareness and allowing the user to control the UI via filters, objects of interest navigate past the user instead of the user navigating to the object. The user operates on a single view without the need for deep menu navigation. The new UI is also easy to configure. We implemented the concept on the Nokia S60 5th edition touch platform and conducted user testing with 16 users. Initially, users felt confused because of new ways of accessing things. However, after a short period of usage, majority of the users found it easy to use. Most of the users felt the system to be fun and playful.