[Live-devel] [live-devel] Too long delay for JPEG live image.

[Raphael KINDT]

Hello,

I've another question.
I observe that there is a difference between my original JPEG header and the
header constructs by the client.
To detect this difference I've used OpenRTSP.

The difference is the quantization table.
I've used a qFactor = 128 and I've overload the
JPEGVideoSource::quantizationTables (with precision = 0 and length = 128).
I've forced the driver (and thus hardware coder) to use the same table as
that which JPEGVideoRTPSource uses.
The driver use 100% for the quality factor.

After all that, there is always a difference.

What can I do to use the same quantization table as that which originals
images use?

Thanks a lot.

-----Message d'origine-----
De : live-devel-bounces at ns.live555.com
[mailto:live-devel-bounces at ns.live555.com]De la part de Ross Finlayson
Envoye : mardi 5 juin 2007 10:36
A : LIVE555 Streaming Media - development & use
Objet : Re: [Live-devel] [live-devel] Too long delay for JPEG live
image.


>Hello,
>
>I'm trying to developpe a MJPEG live streamer server.
>I work with a camera and our specific driver (that I've wrote too)
>for our frame grabber.
>To do this I've learned about Elphel example.
>I've wrote a JPEGVideoSource derivated class then I've overload the
>doGetNextFrame function.
>
>Now I can see remotely live JPEG video from camera with a VLC client
program.
>But I've observe a delay of 2 sec between images received by the
>driver and those received by VLC client.
>It seem there is a too big fifo buffer for live image between them.
>I've disable our fifo buffer to see what's happened.
>Now I copy directly image (30 kB) to FramedSource::fTo data members.
>But the problem is always present.
>
>How can I reduce this delay?

There's no signifcant delay in the "LIVE555 Streaming Media" code -
at either the sending end or the receiving (VLC) end.

However, VLC does have a separate jitter buffer that - by default -
adds 1.2 seconds (1200 ms) at the receiving end.  You can reduce this
by changing VLC's
	Preferences->Input/Codecs->Demuxers->RTP/RTSP->Advanced->Caching
value (ms)

Don't forget also that JPEG encoding (even in hardware) and decoding
also add some delay, which you are unlikely to be able to reduce.
--

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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