How the UrbanDenoiser media player was created?
In this article we want to talk about the process of creation of «UrbanDenoiser» media player. Except its “cute design and slap-up functionality” (which are better described on the official website with the same name) the player has innovative play modes:
- «Denoise» (increases audio intelligibility despite the external noise);
- «World Around” (provides for the possibility to hear audio content and external environment sounds simultaneously);
- «Natural Sound” (player adapts the output signal not only to a specific response of headphones, but also personal characteristics of user’s hearing).
Naturally, these opportunities would not be possible without an innovative signal processing algorithm. We will talk about the process of its creation.
From hearing aids to media players
In early 2014, a team of developers worked on “Petralex” application, which in practice is a digital hearing aid on the basis of a smartphone / tablet. Initially the application was designed for people who have to wear a hearing aid (but feel embarrassed about it). After all, one could never take a smartphone headset for a hearing aid. In addition, a smartphone / tablet has all the hardware components (just like the real – and very expensive! – digital hearing aid). The problem was to develop a “software” capable of real-time audio processing according to user’s personal audiogram (featuring his hearing abilities). By the way audiogram had to be produced by the “software” too.
Therefore, in the hardest and challenging period of work finalization on «Petralex» project two of the team, were in the subway after a hard working day. One of them gave his companion an earphone – to listen to a funny song. However, because of the noise (who was in the subway, knows!) his friend could not make out a single word! Immediately he proposed the idea: to analyze the ambient noise and the useful signal processing to improve its clarity (despite the external noise!).
Friends were inspired by the idea. To further develop the software, several mathematicians joined the team – in order to create the desired algorithm of signal processing (with the use of the experience gained during the development of «Petralex»).
Battle for the algorithm
The main problem was the originality of the problem – no publication on this subject could be found! At first, the developers did not know about the existing analogues. Perhaps this is why they solved the problem in much more original way. They got to know of a similar development at the moment of their own patent execution (on the Western Conferences).
Although it happened later. First signal processing was still very raw. “Real-time” processing was not even discussed. However, for initial debugging this was normal – the aim was to make program module work in principle, to obtain the desired result.
The first prototype of «UrbanDenoiser Player» (or UDP as creators call it), ready to be installed on the phone, was launched five months after the emergence of the idea – in June 2014. Immediately its drawbacks revealed – a mathematical algorithm of signal processing has been very “heavy”!
After all, the main problem in real-time audio processing was to provide a mobile phone (device with significantly limited computing resources) with a simple and efficient algorithm, capable to handle a rapid data stream (44.1 kHz in this case).
Typically, speech-processing frequencies are limited to 8 or 16 kHz. However, since UDP processed music too, the frequency should have been higher.
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Therefore, the resulting algorithm did not work with iPhone 4. Developers had to work harder to optimize the code to fit C code. As a result, they have managed to reduce the level of processor utilization from 55% to 35% for iPhone 5. At that time it was sufficient. Although currently the developers work to further reduce processor utilization level, to make it possible to use UDP on any “hedge Android»).
