Am 20.10.2013 18:08, schrieb Paul LeoNerd Evans: > On Sun, 20 Oct 2013 07:25:23 +0100 > Tanu Kaskinen <tanu.kaskinen at linux.intel.com> wrote: > >> Latency can only increase only if there is some buffer that is >> growing. module-tunnel doesn't have such buffer. It sounds like MPD >> is working so that it writes at a constant pace to an internal >> buffer, and reads from the buffer at the rate that PulseAudio asks >> for more data. If network glitches occur, PulseAudio will ask less >> often, so MPD's buffer will get larger and larger. If this >> speculation is true, then MPD should be fixed. It should define some >> maximum size for the buffer. 30 seconds is silly. And if you're >> playing local files, this whole problem shouldn't exist, because MPD >> should decode the files at the rate PulseAudio is consuming the data, >> not at a constant wall-clock rate. > In fact, I have just used tcpdump to prove this isn't the case. > > Because the TCP tunnel contains pure uncompressed PCM audio, a tcpdump > with hexdump of the raw TCP segments contains pure zeroes during > silence. With mpd paused, I see lots of zeroes go by. > > The /moment/ I unpause mpd, those zeros turn into varying numbers, > containing real audio data. Yet my speakers remain silent... a number > of seconds afterwards, sound now comes out. So then I hit pause. > Instantly, those numbers in tcpdump are all zeroes again, but yet it > takes a number of seconds for the sound to stop coming out of the > speakers. > > This latency is occurring entirely with the tunnel receiver in my > laptop, and not mpd. > Interesting find. That indeed proves pulseaudio at the receiving end accumulates latency. I have always felt it must be that way because the progressbars of all media players I have tried correspond to where the app is at decoding (and not what the speaker output). I wonder if it's really in the tunnel module or somewhere deeper. I also wonder if this works differently with the rewritten tunnel module (this year's GSoC brought it, it's in git master but not released yet). Best regards
