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Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

The lowest-common-denominator SBC codec for Bluetooth seems to have a bad reputation in audiophile circles.  At medium quality (~220 kbps; the default on older versions of Android), it indeed does sound terrible and I was able to ABX it easily when I tried a few months back.  At high quality (~320 kbps; the default on modern Android versions), though, it sounds fine to me in casual listening and I couldn't ABX it when I tried a while back.  SoundExperts.org listening tests seem to give it high marks at this bitrate.  Do others here also find the high bitrate SBC settings transparent and suspect SBC's bad reputation comes entirely from old devices that chose too low a bitrate?

AptX and AAC are marketed as improvements over SBC.  Are there any listening tests to prove that these actually sound better than high-bitrate (~320 kbps) SBC, or is this mostly marketing hype?  Also, isn't AAC significantly more power-hungry than SBC, leading to potentially worse battery life?

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #1
The lower quality may be due to the encoders that were used. SBC is sort of the MP3 of Bluetooth; it's the most compatible, and high bit rates mean high transparency. I've listened to 328 kbps SBC and likewise couldn't tell the difference from original.

None of these formats are lossless, so there isn't much advantage of introducing new codecs other than the issue of transcoding. AAC transcodes well if it can't be sent as is.

As far as power efficiency goes, iPhones have the advantage of a codec chip. Its power usage is small compared to screen and CPU idle, and decodes over 340x real time on an SE.

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #2
You can find explanation why SBC has bad reputation here - https://habr.com/en/post/456182/

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #3
APT is absolutely ancient.  It was never clear to me that it was any better than a reasonable quality SDC encoder, even if it was better marketed.

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #4
$50 to $300 all sound the same.  BT is discouraging.   :-(

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #5
Pretty much the only point of most of the codecs in Bluetooth were to stuff it with patents.

Apple is always against putting open standards in protocols that people will have to use. They tried claiming that they were going to extort money over Canvas, then they got open media codecs gutted from the HTML 5 media standard, they shoved AAC into Bluetooth.

It doesn't do users any good to have to pay for inferior implementations than what are possible, but it does do gigantic patent trolls plenty of good when they can take several thousand of their MPEG patents and stuff them into the web and consumer electronics.

AFAIK, SBC only ever had one patent, and it was free to implement within Bluetooth when it was valid. If the Bluetooth Consortium was like the W3C, Apple would have just complained until it left us with an A2DP standard with no mandatory and free to implement audio codec and then tried shoving AAC down everyone's throats.

No, AAC does not really sound any better than SBC. Tried both codecs on a number of devices and there's really no difference at those bitrates.

 

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #6
APT is absolutely ancient.  It was never clear to me that it was any better than a reasonable quality SDC encoder, even if it was better marketed.
AptX is also an ADPCM codec, so encoding can be really reasonably fast, and decoding is also fast, and the compression artifacts are only likely to show up, if at all, as a hissing noise in the background.

All the reasonable BT codecs are now documented with source code, even if not guaranteed licensing for the effort. Feel free to cook up some code to compare the compression artifacts between them.

SBC is just the lowest common denominator between devices. For instance, my AirPods only support two modes: 44100Hz AAC, and 8kHz full duplex SBC.

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #7
APT is absolutely ancient.  It was never clear to me that it was any better than a reasonable quality SDC encoder, even if it was better marketed.
AptX is also an ADPCM codec, so encoding can be really reasonably fast, and decoding is also fast, and the compression artifacts are only likely to show up, if at all, as a hissing noise in the background.

All the reasonable BT codecs are now documented with source code, even if not guaranteed licensing for the effort. Feel free to cook up some code to compare the compression artifacts between them.

SBC is just the lowest common denominator between devices. For instance, my AirPods only support two modes: 44100Hz AAC, and 8kHz full duplex SBC.

If the (original) aptX is from 1988, it's more than 20 years old (31) and safe to implement, as far as patents go.

As safe as implementing anything can be, that is. Some patent trolls get patents on very obvious ideas and shake people down because it's cheaper than going to court. One of them is suing GNOME right now over a patent and is claiming that they own the right to the idea of a "program that uses a method to import photos from a digital camera". Uhm, okay. I was using programs that did that 20 years ago. I'd like to know how "Rothchild Imaging" got this patent.

As far as source code, you shouldn't look at non-Free code if you're implementing a Free replacement. They can claim that your knowledge of theirs contaminated your implementation and sue you. But someone who has looked at code implementing aptX and who writes a high level spec can make it possible to implement without you having to look at the code itself. This has been done for years, including cloning the PC BIOS.

I don't understand why people would buy Apple products. If there is a mandatory standard, they'll implement it....poorly, and then do everything they can to make it impossible to actually use.

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #8
I bought them because I have Apple devices to use them with, and they mostly sound fine when used with an iPhone in the SBC mode. They only sound like crap when paired with desktops in that mode.

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #9
I once read that the biggest difference between SBC and aptX is, that the latency is lower with aptX. So if that is important aptX has an advantage. But for simply listening to music on your phone that shouldn't matter too much.

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #10
I once read that the biggest difference between SBC and aptX is, that the latency is lower with aptX. So if that is important aptX has an advantage. But for simply listening to music on your phone that shouldn't matter too much.

How much latency was it though?  Outside of simply listening to music, it be interesting to know how much things like video and games were impacted.

Re: Bluetooth: Does SBC Deserve its Bad Reputation? Is AptX/AAC Really Better?

Reply #11
I recently used a BT speaker on a Windows PC and the delay must have been around 300ms, definitely noticeable.

Generally, Bluetooth latency is pretty high. According to this it's over 200ms on Android phones with every codec, in some cases even over 500ms.
Another link regarding iPhones with a video demo: https://stephencoyle.net/latency

There's also aptX Low Latency--not to be confused with regular aptX--which supposedly does sub 40ms latency. But aptX LL is supported by very few devices and it's not trivial to get it working on a PC (it requires special hardware and drivers).

You can simulate audio delay on video files with something like VLC (Tools -> Track Synchronization).

 
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