Re: [Xen-devel] [PATCH v5] sndif: add ABI for Para-virtual sound

[Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxxxxxxxxxxx>]

On Thu, Jan 29, 2015 at 1:45 PM, Vitaly Chernooky
<vitalii.chernookyi@xxxxxxxxxxxxxxx> wrote:
> Ian,
>
> That numbers correspond only particular single usecase - mp3 playback and
> are close to common for that usecase.
>
> For live audio usecases there will be numbers close for common in that
> usecases.
>
> Olexandr,
>
> Could you measure and provide us numbers for some live audio usecase?
Currently we have frontend in the Android.
I've done some measurements:

tinyplay file.wav:
time between samples is about 660 msec

Android media player (mp3 or video file):
time between samples is about 23 msec

So this value is application specific.

Unfortunately I can not measure it for live audio.


> With best regards,
>
> Vitaly Chernooky
>
> On Thu, Jan 22, 2015 at 6:11 PM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> wrote:
>>
>> Oleksandr Dmytryshyn writes ("Re: [Xen-devel] [PATCH v5] sndif: add ABI
>> for Para-virtual sound"):
>> > On Thu, Jan 22, 2015 at 5:56 PM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
>> > wrote:
>> > > Oleksandr Dmytryshyn writes ("Re: [Xen-devel] [PATCH v5] sndif: add
>> > > ABI for Para-virtual sound"):
>> > >> In my case this is about 3 packets per second with size about 16
>> > >> KBytes.
>> > >
>> > > That would put a floor on the latency of about 300ms.  I suspect
>> > > that's quite undesirable.
>> >
>> > This latency doesn't affect us because frontend and backend driver have
>> > an separate thread for each virtualized stream. And when frontend driver
>> > waits answer from the backend it just sleeps (in case Linux kernel it
>> > waits
>> > for the completion).
>>
>> Your seem to be answering a different question to the one I intended
>> to ask.
>>
>> What I mean is this:
>>
>> Many people think it is important to reduce the latency of sound input
>> and output.  So, they want to reduce (a) the time between a piece of
>> software deciding to make a sound and (b) the time when that sound
>> starts to appear.  And the same for input.  This is important for
>> games, video conversations, and so on.
>>
>> When sound output is occurring continuously, any piece of new sound
>> output needs to wait for the next packet to be sent.
>>
>> If you are sending only 3 packets per second then the latency might be
>> as much as 1/3 second which I think is probably too much.
>>
>> Ian.
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel
>
>
>
>
> --
> Vitaly Chernooky | Senior Developer - Product Engineering and Development
> GlobalLogic
> P +380.44.4929695 ext.1136 M +380.98.7920568 S cvv_2k
> www.globallogic.com
>
> http://www.globallogic.com/email_disclaimer.txt

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel