Re: [bump] rygel streaming live audio: low latency?

[Jens Georg <mail jensge org>]

On Mi, 2012-06-13 at 16:27 +0200, Leonardo Gabrielli wrote:

I'm sorry, I somehow missed your answer.

> Thanks for the feedback.
> You are suggesting not compressing in order to reduce latency, right?

Yes. Although the higher amount of data you need to transport might void
that a bit.

> I have read that the current pulse and rygel versions are not working
> correctly. Is this still true?

That depends on what you consider current.

rygel >= 0.14.x and PulseAudio >= 1.0 should do just fine.


> May the high latency I experience depend on the ALSA buffer size?
> If:
> pacmd list | grep -i size
> I obtain device.buffering.buffer_size = "65536" for the default audio
> inputs/outputs. 65k samples at 44100 sampling frequency is more than a
> second! Maybe this can be lowered. Can it be a choice?
> Regards

Uh, that's out of my knowledge, sorry.

> 
> Leonardo
> 
> On 06/13/2012 12:19 AM, Jens Georg wrote: 
> > On Di, 2012-06-12 at 21:24 +0200, andrea zambon wrote:
> > > I tried with Slackware, rygel 0.11 and alsa:
> > > 
> > > [GstLaunch]
> > > enabled=true
> > > launch-items=myaudiosink
> > > myaudiosink-title=Audio on @HOSTNAME@
> > > myaudiosink-mime=audio/x-wav
> > > myaudiosink-launch=alsasrc ! audioconvert ! wavpackenc
> > Wavpackenc does not create WAV. It creates wavpack which is a loss-less
> > but compressed audio format format similar to flac.
> > 
> > Try to set the proper mime-type audio/L16;rate=44100;channels=2 and no
> > encoding or use wavenc. 
> > 
> > Also not that this method is not really meant for pulse integration, it
> > just happened to be the only working way for several pulse and rygel
> > versions.
> > 
> > Using the "native" pulse integration gives you direct access to pulse's
> > HTTP stream.
> > 
> > 
> > > I get 1-2 seconds delay.
> > > I not think that is a problem Rygel.
> > > You try to take the stream from rygel uri and listen to the delay.
> > > 
> > > Note:
> > > I work in a similar project (webcam), but I'm not using Rygel.
> > > I do experiments with a simple application and libsoup, I can send the
> > > raw audio of the microphone toward the TV:
> > > If I use 1 MB buffer, I get 10 seconds of delay.
> > > If I use 1 KB buffer, I get 1-2 second delay.
> > > 
> > > I think that is the best possible result with upnp/dlna media server.
> > > 
> > > Ciao.
> > > 
> > > 
> > > 
> > > 2012/6/12 Leonardo Gabrielli <l gabrielli univpm it>:
> > > > Sorry, for bumping...
> > > > 
> > > > Dear rygel-list members,
> > > > I'm a phd student in Italy and I'm currently trying to stream live audio
> > > > with rygel to other devices. I succeded in doing this by following a method
> > > > using gstreamer input to rygel, here:
> > > > http://chemicaloliver.net/linux/streaming-audio-from-ubuntu-linux-to-a-dlna-player-blu-ray-or-ps3/
> > > > However my goal is to obtain a low latency stream. So far I get 10 seconds
> > > > delay from the live input (e.g. my voice speaking numbers to the microphone
> > > > on the rygel machine) to the renderer machine (another linux machine with
> > > > VLC). This is not related with network problems or other software layers
> > > > (sending audio with other systems I get milliseconds latency). My opinion is
> > > > that such a big delay is due to the connection mechanism which takes approx
> > > > 10 seconds: my idea:
> > > > - the media renderer connects to rygel
> > > > - rygel starts buffering the live audio at once
> > > > - in the meanwhile all the handshaking between rygel and the renderer begins
> > > > and takes some time
> > > > - when everything is ready rygel starts sending the audio to the renderer,
> > > > beginning from the start of the buffer, which is many seconds long now
> > > > - from the media renderer you can listen to an audio signal that is several
> > > > seconds old
> > > > 
> > > > This could be fixed if rygel starts buffering when the connection is ready.
> > > > THe only latency then would be the one from the network and the one from the
> > > > *short* (128 to 1024 samples) buffer.
> > > > 
> > > > I'm not very good in reading or writing code, and I'd like to ask you
> > > > developers if this makes sense to you or this is not the cause of the delay.
> > > > 
> > > > Thanks & cheers
> > > > 
> > > > --
> > > > 
> > > > Leonardo Gabrielli, PhD student
> > > > A3Lab - Dept. Information Engineering
> > > > Università Politecnica delle Marche
> > > > via Brecce Bianche 31, 60131, Ancona, Italy
> > > > 
> > > > 
> > > > 
> > > > --
> > > > 
> > > > Dr. Leonardo Gabrielli, PhD student
> > > > A3Lab - Dept. Information Engineering
> > > > Università Politecnica delle Marche
> > > > via Brecce Bianche 31, 60131, Ancona, Italy
> > > > Skype: leonardo.gabrielli
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> > > 
> > 
> > 
> > 
> > 
> > 
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