On Tue, Apr 3, 2012 at 3:56 AM, qduaty <qduaty@xxxxxxxxx> wrote: > 2012/4/2 Siarhei Siamashka <siarhei.siamashka@xxxxxxxxx>: >> Could you provide a short summary for this whole discussion? The >> discussion has been changing from bitpool negotiation to SBC codec >> improvements back and forth. And now it's becoming hard to follow and >> see which problems are still relevant and need to be solved. Also do >> you want to work on some code yourself or mostly trying to escalate >> the problems? >> >> A2DP is in the list of ideas for BlueZ GSoC, so maybe that's a good >> chance to get some improvements implemented: >> http://www.bluez.org/development/gsoc/gsoc-ideas-list-2012/ > > Ok. This is the summary. > 1. It was found that Bluez can occasionally limit available bitpool > because some devices report a narrow bitpool range that does not > reflect their real capabilities. A solution was proposed by means of > encoding at a higher bitpool than negotiated, and it was confirmed to > both work and not break compatibility, unless it is misused. > 2. It was found that Bluez audio sink has quality problems even on > high bitpools. An SBC encoder fix was proposed, which (re)enables > floating point processing. Tests are needed to confirm whether it > improves quality in all cases. > 3. It was (previously) found and now confirmed that reducing volume in > SBC encoder by a factor of 0.7-0.8 improves quality by eliminating > audible effects of clipping in the decoder. OK, thanks. > For myself, I'm likely to be done with it. I've already solved the > problems that prevented me from using A2DP on Linux. Further work > would require more time and I cannot benefit from it (but students > obviously can). Fair enough. > My proposals: > 1. Introduce a less restrictive input format for the audio sink, such > as float32. Currently it supports only S16LE, which is not suitable > for audio processing (ALSA softvol is a known example). > 2. Find out what quality problems the SBC decoder has and fix them. > Possibly introduce floating point output to eliminate clipping. > 3. Implement proper (adaptive?) clipping prevention in the SBC encoder. -- Best regards, Siarhei Siamashka -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
