H264 compression uncompression delay

[robosara]

Hi all,

Not sure this is the right place to post this. If you have advice on where I should post this, please tell me (even other sites).

For a project, I have to broadcast video on a LAN with low latency.

I have tested the following :
- Acquisition from an analog cam using a matrox card,
- compression in H264 using the same Matrox card (D1 or CIF format),
- broadcasting in LAN using RTP (live555),
- displaying on remote computer using VLC.
=) I obtain a average delay between cam and display of 350ms.

I would like to reduce this delay, and I am looking for hidden time loss.

What is the minimum delay do you think I could reach using such technologies ?
Are H264 and RTP suited for that, or do you think I shoud try other ones ?
If you know how to mathematically compute the minimal delay on some parts of the chain...

Regards

[Jean-Baptiste Kempf]

Did you try decreasing the caching?

[robosara]

Yes, I have played with rtsp-caching/file-caching parameter.
But I cannot set it too low without risking video freezes
Choose a safe value is difficult.

For what I need, I would accept some bad visual effects (lack of data) if VLC was able to just use the minimum cache linked to the frame size, and never stayed frozen...

[Sébastien Escudier]

If vlc does not have enough frames cached it will freeze.
So if you have a lag and a too low caching value, it will freeze.
Caching value depends on your stream network quality, and it may vary across time.
There is no magical values.

[robosara]

So sad VLC encounters difficulties to start again after a lag has occured...
I often have to stop and play to make it operate again.