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



Thanks for the feedback.
You are suggesting not compressing in order to reduce latency, right?
I have read that the current pulse and rygel versions are not working correctly. Is this still true?
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

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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