Apple has quietly made a change that improves audio quality during calls with AirPods 3 and AirPods Pro. The developer Marco Pfeiffer was able to do his tests and research, he shares his findings today.
Better for AirPods audio quality with AAC-ELD
The AAC-ELD codec was invited on the AirPods, it is a variant of AAC. This has been used by Apple for years now, so much so that it is its favorite codec. But now the Enhanced Low Delay (ELD) arrives for communications. It allows the headphones to transfer voice in mono in both directions, and this with a sampling rate of 24,000 Hz thanks to spectral band reconstruction.
Then comes the moment of the call. The AirPods, which are connected via Bluetooth, switch from the A2DP (Advanced Audio Distribution Profile) audio profile to the HFP (Hands Free Profile) to have two-way audio. There are then two codecs that can be used: CVSD for mono in both directions at 8,000 Hz and mSBC for a transfer rate of 16,000 Hz.
After various tests and verifications, Marco Pfeiffer explains that the CVSD codec could technically suffice knowing that the human voice is positioned between 2,000 and 4,000 Hz. But that’s the theory. It is different in practice, hence the choice of AAC-ELD for a much higher sampling rate.
Apple could still improve, but Bluetooth remains a hindrance because of its bandwidth. Apple had recognized it a few weeks ago. It makes you wonder if the manufacturer is not trying to create another way to have more control.