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My understanding is that the AirPods and iphone have a high quality codec that isn’t widely supported yet ...

by rusk 6y ago

willtim 6y ago
My understanding is that music gets decompressed on the Apple headphones, the original AAC stream is sent over the wire. Most Bluetooth headphones will just effectively transcode the audio, such that for example AAC gets decompressed then recompressed into AptX/LDAC. For music listening, it's completely suboptimal. I use FLAC sources for my Sony headphones which makes them very listenable (along with copious EQ to tame the +5db excess bass). Bluetooth headphones have a lot of room for improvement.
- em500 6y ago
  > My understanding is that music gets decompressed on the Apple headphones, the original AAC stream is sent over the wire. That's claimed at many places, but this one claims the opposite: https://habr.com/en/post/456182/ https://habr.com/en/post/456182/, that everything gets (re-)compressed into AAC on the sending device before sending it to the Airpods, in order to mux other audio events. In principle, with end-to-end Apple hardware, they could send multiple streams and leave the muxing to the Airpods, but I don't think anyone has conclusively shown if this is actually done.
  - deleted 6y ago
    [deleted]
  - marcan_42 6y ago
    If there's one thing I've learned about technical claims about Apple hardware, it's that they are not to be believed unless they come straight from Apple in a precise and unambiguous statement, or from a reverse engineer/hacker who has looked at the code/protocols. The reality distortion field is just as strong as always when it comes to technical details too. People will make random things up to prove that Apple is different or (more) special.
- marcan_42 6y ago
  Claims of poor Bluetooth audio quality generally fall into the following categories: * Bad source settings/implementation (i.e. bitrate too low) * Bad sink implementation/EQ/DAC * The HSP issue referenced by OP (where you can't have both HQ audio and use the mic) * FUD by patented codec authors The reality is that even the basic royalty free Bluetooth SBC codec is perfectly fine, and sounds transparent at high bitrate settings, which decent sources should be using and all sinks are required to support. Transcoding doesn't make much of a difference either. It's a poor codec, but the bitrate is high enough that it doesn't matter. You can ABX test it yourself if you're so inclined, purely in software, with high quality wired audio hardware. I have. You'll see the codec isn't the problem. So when your Bluetooth device sounds better wired than wireless, or works better with AptX or some other patented nonsense codec - most likely the problem is careless software/firmware (or outright crippling to push patent licenses), not the spec being bad. (I say this as someone who was gotten into flamewars over the quality of ffmpeg's AAC implementation and found bugs in the Opus reference encoder; I can tell when audio quality drops)
  - willtim 6y ago
    > Transcoding doesn't make much of a difference either. I respectfully disagree. Transcoding does make an audible difference, at the bitrates typically used, and should have no place in "high fidelity" audio. My issue with these Bluetooth codecs is that they are not used at the sources and so will always be used in practice for transcoding.
    - marcan_42 6y ago
      Have you ABX tested an SBC transcode at the maximum bitpool settings vs the original? Because I have, and I couldn't tell the difference. The "transcoding is bad" story is about low quality settings, archival, and/or bad encoders. E.g. don't do repeated transcodes with the ffmpeg AAC encoder, not even at 320kbps. But one final transcode with SBC for over-the-air delivery at the max allowed bitrate? That's totally fine, especially for typical Bluetooth use cases (listening on the go, casual headphones, etc).
      - 6y ago

My understanding is that the AirPods and iphone have a high quality codec that isn’t widely supported yet ...

by rusk 6y ago

My understanding is that the AirPods and iphone have a high quality codec that isn’t widely supported yet ...

My understanding is that music gets decompressed on the Apple headphones, the original AAC stream is sent over the wire. Most Bluetooth headphones will just effectively transcode the audio, such that for example AAC gets decompressed then recompressed into AptX/LDAC. For music listening, it's completely suboptimal. I use FLAC sources for my Sony headphones which makes them very listenable (along with copious EQ to tame the +5db excess bass). Bluetooth headphones have a lot of room for improvement.

em500 6y ago
> My understanding is that music gets decompressed on the Apple headphones, the original AAC stream is sent over the wire. That's claimed at many places, but this one claims the opposite: https://habr.com/en/post/456182/ https://habr.com/en/post/456182/, that everything gets (re-)compressed into AAC on the sending device before sending it to the Airpods, in order to mux other audio events. In principle, with end-to-end Apple hardware, they could send multiple streams and leave the muxing to the Airpods, but I don't think anyone has conclusively shown if this is actually done.
- deleted 6y ago
  [deleted]
- marcan_42 6y ago
  If there's one thing I've learned about technical claims about Apple hardware, it's that they are not to be believed unless they come straight from Apple in a precise and unambiguous statement, or from a reverse engineer/hacker who has looked at the code/protocols. The reality distortion field is just as strong as always when it comes to technical details too. People will make random things up to prove that Apple is different or (more) special.
marcan_42 6y ago
Claims of poor Bluetooth audio quality generally fall into the following categories: * Bad source settings/implementation (i.e. bitrate too low) * Bad sink implementation/EQ/DAC * The HSP issue referenced by OP (where you can't have both HQ audio and use the mic) * FUD by patented codec authors The reality is that even the basic royalty free Bluetooth SBC codec is perfectly fine, and sounds transparent at high bitrate settings, which decent sources should be using and all sinks are required to support. Transcoding doesn't make much of a difference either. It's a poor codec, but the bitrate is high enough that it doesn't matter. You can ABX test it yourself if you're so inclined, purely in software, with high quality wired audio hardware. I have. You'll see the codec isn't the problem. So when your Bluetooth device sounds better wired than wireless, or works better with AptX or some other patented nonsense codec - most likely the problem is careless software/firmware (or outright crippling to push patent licenses), not the spec being bad. (I say this as someone who was gotten into flamewars over the quality of ffmpeg's AAC implementation and found bugs in the Opus reference encoder; I can tell when audio quality drops)
- willtim 6y ago
  > Transcoding doesn't make much of a difference either. I respectfully disagree. Transcoding does make an audible difference, at the bitrates typically used, and should have no place in "high fidelity" audio. My issue with these Bluetooth codecs is that they are not used at the sources and so will always be used in practice for transcoding.
  - marcan_42 6y ago
    Have you ABX tested an SBC transcode at the maximum bitpool settings vs the original? Because I have, and I couldn't tell the difference. The "transcoding is bad" story is about low quality settings, archival, and/or bad encoders. E.g. don't do repeated transcodes with the ffmpeg AAC encoder, not even at 320kbps. But one final transcode with SBC for over-the-air delivery at the max allowed bitrate? That's totally fine, especially for typical Bluetooth use cases (listening on the go, casual headphones, etc).
    - 6y ago