• Bluetooth stack modifications to improve audio quality on headphones without AAC, aptX, or LDAC codecs

      Before reading this article, it is recommended to read the previous one: Audio over Bluetooth: most detailed information about profiles, codecs, and devices / по-русски

      Some wireless headphone users note low sound quality and lack of high frequencies when using the standard Bluetooth SBC codec, which is supported by all headphones and other Bluetooth audio devices. A common recommendation to get better sound quality is to buy devices and headphones with aptX or LDAC codecs support. These codecs require licensing fees, that's why devices with them are more expensive.

      It turns out that the low quality of SBC is caused by artificial limitations of all current Bluetooth stacks and headphones' configuration, and this limitation can be circumvented on any existing device with software modification only.
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    • Audio over Bluetooth: most detailed information about profiles, codecs, and devices

        XKCD comic. How standards proliferate. SITUATION: there are 14 competing standards. Geek: 14?! Ridiculous! We need to develop one universal standard that covery everyone's use cases. Geek's girlfriend: yeah! SOON: Situation: there are 15 competing standards.

        This article is also available in Russian / Эта статья также доступна на русском языке

        The mass market of smartphones without the 3.5 mm audio jack changed headphones industry, wireless Bluetooth headphones have become the main way to listen to music and communicate in headset mode for many users.
        Bluetooth device manufacturers rarely disclose detailed product specifications, and Bluetooth audio articles on the Internet are contradictory and sometimes incorrect. They do not tell about all the features, and often publish the same false information.
        Let's try to understand the protocol, the capabilities of Bluetooth stacks, headphones and speakers, Bluetooth codecs for music and speech, find out what affects the quality of the transmitted audio and the delay, learn how to capture and decode information about supported codecs and other device features.

        TL;DR:

        • SBC codec is OK
        • Headphones have their own per-codec equalizer and post processing configuration
        • aptX is not as good as the advertisements say
        • LDAC is a marketing fluff
        • Voice audio quality is still low
        • Browsers are able to execute audio encoders compiled to WebAssembly from C using emscripten, and they won't even lag.

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      • Choosing true wireless earbuds: 6 months later…

        • Translation


        Once I put on true wireless headphones and all the cables after that (even if it's a flexible headband on a “wireless” headset), became annoying. So I’ve tried a lot of AirPods-like earbuds in order to find the best ones. In 2018 aside from the AirPods themselves I tried: Jabra Elite 65+, Samsung IconX 2018 and Sony WF-1000X. The result was a neat table with all the objective data. Everything else — my personal opinion — let's discuss in the comments.
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      • 6 Applications for the Industrial IoT

          “Come on, baby, what’s wrong? Tell me what you need,” my uncle Nicholas was shredding up his old car’s engine, which totally refused to start. Being a schoolboy back then, I was absolutely sure that any exhortation my uncle voiced was powerless against a dumb ton of metal. Talking to a car was just a psychological trick that probably helped my uncle cope with exasperation. Moreover, neither me nor my uncle believed in a possibility to communicate with “dead metal” sometime in the near future. That was in the mid-1980s. When I reached the age of my uncle, the situation changed radically.
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