it seems when most people reply to the "apt-x vs LDAC?" question the replies are about apt-x HD vs LDAC, when in preactice there are actually many less devices that support apt-x HD (not just regular apt-x) than support LDAC. these days almost all android phones for instance support LDAC and apt-x but not apt-x HD. so is there a clear differnce between (non HD) apt-x and LDAC?
First, have a read at this:
https://www.androidauthority.com/sony-ldac-codec-790690/
Note that there are 3 variants of LDAC: 330 (connection preferred), 660 (normal) and 990 (SQ preferred) kbps, namely referring to how fast the transfer rate / connection speed between the source (i.e. smartphone) and the receiver's end (i.e.BT adapter, headphone, etc). Some smartphone allows only two options (best effort for a mix of 330 and 660, or best SQ for a mix of 660 and 990). Of course, the faster the transmission rate, the better the SQ (less compression) but the less stable the connection. Purely on how lossless the transmission is, aptX is roughly the same / slightly better than LDAC 330 while apt HD is about the level of LDAC 660. So it is never quite an one-to-one comparison when you compared aptX to LDAC, but actually which LDAC (330, 660 or 990) that you are comparing to - aptX to LDAC 330 can go both ways (*you might even prefer high bitrate SBC or AAC over them both), aptX to LDAC 600 might have some small difference but aptX to LDAC 990 should be fairly distinguishable to the ears.
On a side note, the lack of popularity of aptX HD has to do with the lack of compatible BT chipset from Qualcomm, as aptX HD requited the BT chip to be able to handle 24bits yet most Qualcomm BT chips are 16bits only. So aptX HD is almost exclusively implemented on Qualcomm's best BT chip at the time, the CSR8675. On the other hand, If you look at LDAC - which required 24/96, but no specific chips requited. However, Qualcomm already dominated BT chip market anyway so most of the gears are build on the same CSR8675 chipset - that means any BT adapter / headphone maker that wants the best BT chips can have a choice of two codecs, and many picked LDAC since it is backed by Sony (more famous and thus better for marketing) and offer better SQ than aptX HD (well, for the most part user get both supported on the same gear anyway). SO while apx HD never quite get as much exposure as LDAC, Qualcomm still makes money since almsot all LDAC gear uses the Qualcomm BT chip (which also supports aptX HD, though some time manufacturer decided to disable it on the firmware level to simplify implementation and only opted to support LDAC). Personally, I think LDAC being more popular also has a lot to do with Sony's better marketing.
