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Topic: Personal blind comparison of the Bluetooth codecs, AAC vs LC3, re-encoding (Read 13824 times) previous topic - next topic
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Re: Personal blind comparison of the Bluetooth codecs, AAC vs LC3, re-encoding

Reply #25
Hello. My name is Alexander from Fraunhofer IIS.


Wow, as in Dr. Alexander M., the director at Fraunhofer IIS?!? Welcome!  :)

Re: Personal blind comparison of the Bluetooth codecs, AAC vs LC3, re-encoding

Reply #26
Hello, and thanks to HolyMusic for the detailed analysis.

For TWS ear buds (and likely for any other audio device), each audio channel is transmitted via individual transport channels. AAC-LC uses joint stereo coding which means that the payload sent to each device contains both channels (e.g., 160 kbps) while with LC3 just the corresponding channel (80 kbps) is sent to each ear-piece. At this point the Low Energy factor kicks in as energy consumption is mainly related to the payload size sent over the air. Even if LC3 is using a higher bitrate (e.g., 96 kbps or 124 kbps per channel), the payload size sent through the air is lower compared to AAC-LC (160 kbps per channel).

Good point. What I have done is to select settings so that the bitrate, in a classical file-based sense, will be equal; not the payload size sent over the air, according to the each Bluetooth protocol.

The following argument assumes True Wireless Stereo (TWS).

With Bluetooth Classic Audio, both channels have to be sent over the air to the left earbud first, and then, the left earbud have to carry the burden of having to transmit the entire payload over the air to the right earbud. Joint stereo coding means there is no easy way to avoid having to carry the left-side contents to the right earbud.

With Bluetooth LE Audio, the smartphone only needs to send the left sound to the left earbud and the right sound to the right earbud, easy, which is just fine because LC3 use simple stereo when the bit rate is 128k or more.

So, in this particular setting tested in this listening test, the total payload will be smaller in LC3.

Thank you for confirming our observations. Good to hear that our views align.