On Wed, May 04, 2011 at 12:15:57PM +0300, Kai Vehmanen wrote: > Hi, > > On Wed, 6 Apr 2011, Ken Restivo wrote: > >> I have been lately using a Bluetooth A2DP headset to listen to music. >> >> Every now and then, it drops pitch! It slows the music down, by as much >> as a semitone, for several seconds, then comes back slowly. I rather >> like the effect; it's like an old cheap analog vynil turntable with a >> bad motor or worn belt. > > what headset are you using? I recommend getting a different headset if > you want to get rid of this (or cherish the headset you have, if you like > the effect ;)). > > Some parts of BT A2DP are a bit underspecified and there are some > interesting implementations of it out there. There is no flow control or > clock sync used, so the receiver (your headset) should be a proper > RTP-receiver type of implementation that can adjust to the sender's clock > and packet transmission rate and adjust for drift, etc. > > But there are some headsets that are lazy and make false assumptions on > the timing characterics of A2DP and the sender. E.g. I've stumbled on > commercially sold headsets that just play at whatever rate the sender is > sending. So you get incorrect and _varying_ pitch for all played audio. > The exact outcome is unique to each sender+receiver combo. > > In your case, the headset seems to have some funky underrun/overflow > logic that tries to periodically catch up, or slow down, in case of clock > drift (which to some degree always happens). Yep. It cost all of US$12, shipped directly from Hong Kong (took 3 weeks to get here). Not surprised that it has bugs. I'm fine with it for now. Thanks for explaining! -ken _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
