On Sat, 2014-02-15 at 02:52 +0100, Malte Gell wrote: > I get these sync issues when I use my bluetooth headphone. > > It seems pulseaudio has an issue with bluetooth audio, I find these > messages in /var/log/messages: > > module-bluetooth-device.c: Skipping 306252 us (= 54020 bytes) in audio > stream > > Is this a bug that needs to be fixed or can it be fixed with > configuration changes? The skipping of audio is not necessarily abnormal, because wireless links are inherently unreliable. Packets get dropped, there's nothing we can do about that. On the topic of audio/video sync, synchronization requires accurate latency information. PulseAudio doesn't have that information. If the audio lags by a constant amount all the time, then you can work around the problem by configuring the latency offset with e.g. pavucontrol. If the audio lags more and more over time, however, that's means that buffering increases somewhere, and the configurable latency offset is not a viable solution. I don't think PulseAudio increases any of its buffering, so the buffers grow either in the kernel, in the local Bluetooth chip or in the remote device. It would be good if the kernel could tell PulseAudio how big the local buffers are and what is their fill level, but I don't know if there's any interface for that. If there is, PulseAudio doesn't use it currently. It would be valuable information if someone could research this and tell if there is such interface, or if such interface could be added. Then PulseAudio's Bluetooth latency handling could be improved. If the buffering increases in the remote device, however, then there's absolutely nothing that we can do (assuming that there's no interface in the Bluetooth spec for reporting the latency information from the remote device to the local device). -- Tanu
