The VideoLAN Forums

Posted: **06 Apr 2006 02:06**

G'day,

I am using vlc-0.8.4a to monitor lab equipment using an Apple iSight Firewire camera and Andrea Guzzo's dc1394 input module.

I have configured VLM to provide audio-visual streams playable in Windows Media Player and JPEG stills/snapshots that can be viewed from any web browser for people without broadband connections.

I generated JPEG stills by using the mjpg codec with the 'raw' mux module.

The problem is that once in a while, I receive invalid JPEG image data that does not display. If I refresh the image again, the next frame appears correctly. The problem normally happens at least once for every 20 refreshes.

When I have examined the actual data in the bad frame, it is missing a JPEG header.

Here is my VLM configuration:

Code: Select all

new camera1 broadcast enabled
setup camera1 input dc1394:/dev/video1394/0:camera=0:size=320x240:adev=/dev/dsp
:channels=1:fps=15
setup camera1 output #duplicate{dst="transcode{vcodec=DIV3,vb=256,acodec=mp3,ab=
32}:std{access=mmsh,mux=asfh,url=:9192/stream1_v_medium.asf}",dst="transcode{vco
dec=MJPG,vb=4000}:std{access=http,mux=raw,url=:9192/stream1.jpg}"}

control camera1 play

Any help in finding the cause is much appreciated.

Regards, Vlad.

Posted: **07 Apr 2006 04:11**

OK, I made some progress.

I now believe that I am using VLC in a way that it is not technically designed to be (but should be).

My intention was to obtain JPEG stills/snapshots by using the MJPEG codec with the raw muxer.

When I retrieved images manually using wget, I found that individual frames were not being downloaded, but instead a continuous stream of JPEG images.

I suspect that the reason why it appeared to be working is that most of the time, the web browser happens to stumble upon a valid image in that stream and then terminate the HTTP connection.

The rest of the time, the browser connects when we are part-way through an image, sees what looks like garbage data, and then gives up.

I would be grateful if one of the developers could modify the existing code to properly support JPEG stills.

Posted: **20 Oct 2006 15:58**

Hi,

Same problem, have you solve it now?

Thanks for help

Posted: **21 Oct 2006 12:27**

Nope, problem still exists

I really wish a developer would look into this - that is, provide proper support for periodically updated JPEG snapshots of a video stream.

Also, I don't think the mixed/replace headers produced by the mpjpeg mux are completely correct - they might work for the Axis client (I haven't tested), but they should be able to be viewed by Internet Explorer, for the first frame of the video stream.

4 years ago, I used Jon Travis's camserv to stream mpjpeg video and you could view the first frame in internet explorer (motion video would require netscape/mozilla/firefox which properly implement mixed/replace support).

I think fixing the mpjpeg module to produce headers that are more compatible across browsers would not be too difficult.

The VideoLAN Forums

Sporadic corruption of JPEG stills

Sporadic corruption of JPEG stills

Sporadic corruption of JPEG stills

Sporadic corruption of JPEG stills