On 22.03.2016 12:57, Georg Chini wrote: > On 22.03.2016 12:51, Tanu Kaskinen wrote: >> On Tue, 2016-03-22 at 12:33 +0100, Georg Chini wrote: >>> On 22.03.2016 12:20, Tanu Kaskinen wrote: >>>> On Tue, 2016-03-22 at 10:11 +0100, Georg Chini wrote: >>>>> Hi, >>>>> >>>>> when a sink is started, there is some delay before the first >>>>> sample is >>>>> really played. >>>>> This delay is a constant part of the sink latency that will be always >>>>> present, so the >>>>> minimum sink latency cannot go below that start delay. >>>>> Would it be acceptable to adjust the latency range for the device >>>>> after >>>>> each unsuspend >>>>> to reflect that? >>>>> USB devices (those I have access to) for example have a startup >>>>> delay in >>>>> the range of >>>>> 10ms, but have a latency range that starts at 0.5ms which does not >>>>> make >>>>> a lot of sense >>>>> in my opinion. >>>> I don't understand why the startup delay would limit the minimum >>>> latency once the stream is flowing. Imagine a sound card that is >>>> powered by a nuclear power plant. I don't know how long it takes to >>>> start a nuclear power plant, but let's say it takes a couple of days. >>>> Now the sound card startup delay is a couple of days, but there's no >>>> reason that the audio latency has to be a couple of days once the >>>> power >>>> plant is running. Where would all that audio be buffered anyway? >>>> >>> Hi Tanu, >>> >>> you are wrong. >> I don't believe you :) > Look at the code of alsa-sink. It never drops samples. The only way to > compensate > for the startup delay would be to drop audio as long as the sink is > not yet playing, > but that is not done. I could try to implement that however and then > you would be > right, but with the current code at least for the alsa-sink the > startup delay will persist. In fact, the first data is pushed to the sound card even before snd_pcm_start(), so dropping audio seems to be difficult. We would have to feed silence to the card until we are sure it is playing and drop audio during that period.
