[vlc] Re: How to do a live stream with minimum latency?

[Les LaZar]

----- Original Message ----- 
From: "Alexander Isacson" <alexander at isacson.info>
To: <vlc at videolan.org>
Sent: Friday, May 14, 2004 2:58 PM
Subject: [vlc] Re: How to do a live stream with minimum latency?

[snip]

> The BT878
> has about 500ms latency just showing the stream on a local screen (from
> what I hear).

Alexander,

I believe you are mistaken regarding latency enherent in the BT878.

I am running a 1GHz Via C3 under Fedora Core 1.  Using the xawtv that comes
in the FC1 distribution and a WinTV Go card, I can see no decernable delay
between what the camera sees and what is displayed on the monitor.
Undoubtedly there is some delay, but it must be in single or low double
digit milliseconds to be unseen, especially when I am looking for it.

On the same system, running VLC, just camera to display (command:  vlc
v4l:/dev/video0:channel=1:norm=ntsc) displays the camera image in a 320 x
240 window.  The observed latency (delay from something happening in front
of the camera until it is displayed on the monitor) is estimated (by me) to
be in the 500-600ms range.  This affects the audio as well.  If I snap my
finger in front of the camera (with a mic feeding the audio input), I see
and hear that snap about 1/2 sec later.

Conclusion:  the latency we observe with VLC is all due to the hardware.

I had hoped to use VLC for a closed loop robotic control system.  Currently
this is not possible on the hardware platform I wish to use (two 1GHz Via C3
EPIA-M motherboards connected with a dedicated 100Mbs ethernet link).  On
this system VLC will not even stream video from one system to the other...it
cannot encode the frames fast enough.  At the moment I am using GnomeMeeting
for the video and audio streaming functions, although it has latency,
resolution and other problems of its own, at least it CAN stream video and
audio on the hardware I plan to use.

Les


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