2011/10/18 Siarhei Siamashka <siarhei.siamashka@xxxxxxxxx>: > Still I would suggest you to try the attached patch just for a test. > It reduces audio volume as part of the sbc encoding process and should > eliminate most of the possible clipping cases on the decoding side. Sorry for responding after a half year :) but I finally tested your encoder patch applied to libbluetooth version 4.96, using AIMP3 and pulseaudio. Unpatched encoder produces a "digital" distortion (which is rather annoying) and sounds much like BlueSoleil on Windows. After patching, music is slightly quieter (which can be expected if you decreased its volume) and has an "analog overdrive" like through a cheap FM radio. Anyway, the annoying "digital" distortion that was present in unpatched encoder, is now gone. Some fluctuations can be heard in higher bands in classical music, and (as expected) instruments are indistinguishable, but it's acceptable given the low bitpool. For the "analog overdrive" I hear, it may also come from the device itself (its proper name is Nokia BH-503). Considering its glue sealed case, it might have been designed as a budget solution and its price was "adjusted" due to no competition. > Using bitpool 128 is kind of weird for SBC codec, because the encoded > data stream has about the same size as the the original data and this > defeats the whole purpose of having any lossy compression at all. Yes, but who needs a lossy compression in an endpoint? SBC and MP3 were introduced to overcome the low throughput problem of the bluetooth link, which is no longer the case since 2.0+EDR has plenty of unused bits. > I still recommend you to try sbcenc/sbcdec tools for the experiments with audio quality. I tried them some time ago, but I believe ALSA backend may serve for the same purpose (and is much easier to use). 8 blocks seems to sound slightly better than 16 for classical music, full stereo eliminates the floating of virtual sound sources, 48 kHz also seems to increase quality a bit when compared to 44.1. Regards -- Sebastian Olter -- 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
