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Comment by jsheard | Hacker News Reader

Indeed it's just the encoders. Qualcomm seems to reserve the decoders as a unique selling point for their silicon, as far as I can tell they won't license them out for use on any competing hardware. Every teardown I've seen of a device which supports decoding aptX has had a Qualcomm Bluetooth SoC inside.

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Last time I worked with aptx directly was in the CSR days, but they used to have a library they'd provide in binary form only for your specific platform and compiler settings. It was fuck-off expensive ($1+/device + certification), so the easier way to do things was just to buy their silicon which had the IP "for free". A couple years back someone put a decoder of dubious legality into FFMPEG [1], though. The code was subsequently migrated into bluez as well.

[1] https://ffmpeg.org/doxygen/trunk/aptx_8c_source.html

>dubious legality into FFMPEG

Why dubious ? FFMPEG is not incorporated in the US and does not recognize software patents. All the popular codecs such as h264, h265, etc. are similar in nature.

Because it was reverse engineered from binaries, not cleanroom. I certainly wouldn't risk using it for a product, much less advertise it as a feature given Qualcomm's history in this space and the myriad ways they can make your life absolute hell even if you're 100% in the right. Qualcomm is not a nice company.

I meant that a large number of codecs supported by FFMPEG are patent encumbered, and nobody ships them in the US. This is well known. Even distros based in the US such as Fedora/RHEL do not ship them out of the box. So clean room v/s reverse engineered gets into a secondary issue that is mostly moot.

Sure, but since Qualcomm is never going to give anyone a license to use it and the lack of cleanroom means the provenance is somewhat uncertain, I think "dubiously legal" is a perfectly acceptable description. It's not like I'm saying it shouldn't exist or anything. Just, be aware that the semiconductor mafia considers this part of their turf and wear some kneepads if you're going to make money with it.

Hmm, why do such decoders even need silicon? Decoding is a software thing and even 386 computers could decode MP3 in realtime in the 90s

They don't, as OP said, its just a feature you only get if you run your SW on their silicon.

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