[pulseaudio-discuss] Why does a VOIP sink input's current latency become "0" after moving to a new sink? I saw endless "rewind" in log

[xing wang]

2011/6/2 xing wang <wangxingchao2011 at gmail.com>:
> 2011/6/2 Lin, Mengdong <mengdong.lin at intel.com>:
>> I’m working on a module that can switch profile for a Bluetooth headset:
>> A2DP for music playback and HSP for a phone.
>>
>> When this module detects a sink-input-put event of a “phone” like GTalk and
>> Bluetooth is the default sink, it can change BT profile from A2DP to HSP if
>> necessary. Then the A2DP sink is deleted, and the phone’s input stream will
>> be routed to the new HSP Bluetooth sink.
>>
>>
>>
>> My problem is: I cannot hear good voice from the other side of GTalk, I get
>> bursts of audio (about 2 seconds) followed by very long bursts of silence.
>>
>> By using pacmd, I found that Gtalk input stream is connected to the BT HSP
>> sink, but GTalk input stream’s latency is “0”, very strange. Like this:
>>
>>
> Mengdong, current latency of the sink-input is calculated by
> pa_sink_input_get_latency(), you can check details there. For the "0"
> result, there're two "if" conditions in
> pa_sink_get_latency_within_thread(). If the sink's state is
> "suspended"(from your log,it's running" or sink doesnot support
> "PA_SINK_LATENCY", the current latency will be 0. otherwise, there's a
> real calculation function in sink_get_latency() in alsa-sink.c.let's
> further check the conditions.
>
>
Hi mengdong, pls ignore above wrong explanation. Colin's answer about
the latency is right.
what i said is sink's latency, not sink-input.

Cool work, Colin!

thanks
--xingchao