Hi Arun, On Tue, Sep 18, 2018 at 9:02 PM, Arun Raghavan <arun at arunraghavan.net> wrote: > On Wed, 12 Sep 2018, at 4:12 PM, Pali Rohár wrote: >> Hello! >> >> I would like to let you know that Serge from soundexpert.org did in last >> month some research on aptX and its quality. Detailed article is on the >> following website, specially see parts added around "August 2018": >> >> http://soundexpert.org/news/-/blogs/audio-quality-of-bluetooth-aptx >> >> ============ >> Conclusions: >> >> aptX codec used in BT applications is no better than SBC at 328. Despite >> slightly lower algorithmic delay of aptX both SBC and aptX codecs >> provide the same 100-150ms latency in real-life BT applications. >> >> If you hear the difference between SBC and aptX in some BT product, >> there can be only two explanations - placebo effect or using SBC in >> Middle or Low Quality modes. >> >> AptX is just a copper-less overpriced audio cable. >> >> aptX HD is high-bitrate version of aptX. It has clearly noticeable >> increase in sound quality (not dramatic though taking into account the >> increase in bitrate) >> ============ >> >> And it just confirms my own testing. Whatever I did I was not able to >> either hear or see difference between aptX and SBC encoded-->decoded >> audio. >> >> I had discussion with Serge and there are some ideas which Linux >> Bluetooth A2DP software could supports: >> >> 1) Allow user to specify SBC codec quality. In most cases, including >> pulseaudio, SBC quality is chosen either to middle or low, not to >> maximum bitpool. In some cases SBC at high quality can provide better >> quality as aptX and more important -- SBC is supported by all headsets. >> >> 2) Show user current SBC codec quality. So user would know what was >> chosen and what should expect. I was told that Windows's Toshiba >> bluetooth stack has support for this indication. >> >> 3) In some cases SBC SNR bit allocation method can provide better >> quality as SBC loudness method. > > Thanks for sharing, this is very interesting. > >> So then I could ask question: >> >> 1) What to do with aptX? It is really useful for users to have it in >> Linux & pulseaudio? Because it looks like that the only thing which it >> has better is lower latency. But can pulseaudio on Linux system really >> achieve it? > > What would prevent us from doing so? > >> 2) Should we rather look at increasing quality of SBC codec in >> pulseaudio? And if yes, how should be quality of SBC configured? Via >> profiles? Or to invent some new protocol options? Can we increase >> default SBC bitpool allocation? > > My preference is to not expose things to the user but try to move towards > >> 3) If aptX is decided as useless, what about aptX HD codec? aptX HD >> codec is supported by less products (currently I do not own any), but >> this one may provide better quality as SBC according to that research. > > Right, could still be worth it indeed. > >> PS: That aptX research is the first and the only one about which I know. >> All other information about quality or other details which I found on >> internet are just marking informations. > > In general, it seems the work to support other codecs could still be valuable for AAC and maybe in the future, LDAC? Is anyone aware of a similar comparison for the either of these codecs? > > AAC is still interesting for passthrough media, of course (I hope to have more on the ability to support that in coming weeks/months). Any objective information on LDAC would be interesting too. Afaik Android supports LDAC so at least for headset/carkits using PA that would be a good addition, though it requires even higher bitrate: https://www.androidauthority.com/sony-ldac-codec-790690/ -- Luiz Augusto von Dentz
