The VideoLAN Forums

Hi,

I've had a vlm file that's been working for a very long time in Linux Mint 15. I believe Mint 15 was based off Ubuntu 12. The vlm creates a mosaic of 6 vl42 devices which use 3 separate hardware devices and hence 3 different drivers. One device is a 4 port card. This had been working fine until I upgraded to Mint 17, which is based off Ubuntu 14. Anyhow, here's the vlm file:
I run the vlm file with the following command line:
Ok, I lied. I use a script that writes the vlm file and runs the command line, but the end result is the same. The script is here, for the sake of literally showing what I do:

https://gist.github.com/DanielCeregatti ... 5f5b7cb6f7

Note that the only difference between what I've posted and the script is that the script tries to run v4l2-ctl on the devices to make sure they're configured properly. This was necessary in Mint 15, where vlc 2.0.8 was used, but now it does not affect the stream at all.

Anyhow, since upgrading, the stream no longer works. Right now the "webcam" device is the only one showing a proper picture. The bttv camera seems to not have set the correct standard, as the image is green and fuzzy, and the other 4 on the saa7134 are completely blank. I've read a few other posts where it's been suggested this is a driver issue, but other apps such as mplayer and xawtv work perfectly with these devices. This leads me to believe it is NOT a driver issue.

Here is the output when I run the script with -vvv (The forum complained that I exceeded the 60k max character limit, so I put the file on my own web server):

http://ceregatti.org/log

I've also tried the 2.2.0 PPA, which installed a 3.0.0-git version, but this seg faulted. I'm willing to try the PPA version again if new builds happen nightly, as the PPA seems to suggest they do.

I've even tried running the old vlc in a chroot on the new machine (I had saved the previous root filesystem under /old). This yielded the same problems, where the v4l2 devices simply were not configured properly.

I'm hoping someone has some insights. And BTW, I'm lurking on IRC in #videolan on freenode as Primer. Feel free to contact me there directly.

Thanks,

Daniel

I cannot reproduce the frame size problem. VLC 3.0.0 with the V4L2 test device in I420 at 320x240 works fine here.

Ok, here's a simpler example:
This example uses the bttv device, which is the device that is currently showing up as green and fuzzy, implying that the standard is not set properly. Sure enough, that's what shows in the log:
The two interesting lines in this log, IMO, are:
So I'm taking this a step further with strace. The file is too big to include here directly, so the entire strace is on my server:

http://ceregatti.org/strace_log.txt

Here are the interesting bits:
and the subsequent write to stderr:
And the other one:
And its stderr:
I'm no v4l2 expert by any means, but the fact that this device works perfectly in xawtv and mplayer imply that this is not a driver problem. From what I'm seeing here, whatever is issuing those calls is at fault. Can we at least agree on that? I'm willing to do whatever it takes to diagnose this problem, so feel free to suggest steps.

Daniel

VLC is correctly complaining that your device needs a video standard and none were specified on the command line (zero is the default value): As for the rest, it means VLC cannot get the frame rate informations because the driver sucks. This is not generally fatal but it may affect streaming.

Except the problem still exists if I only do this:
Log:
Surely this can't be desired behavior? I'll grant that perhaps the driver sucks, but other programs which are also using libv4l* and friends work fine. Example:
Screen shot of mplayer:



And here's vlc:
Screen shot of vlc:



Again, this was all working fine on Mint 15/Ubuntu 12 kernel 3.8.0-35 on vlc 2.0.8. The difference now is Mint 17/Ubuntu 14, kernel 3.13.0-24 on vlc 2.1.5. I've seen a few other posts here on the forums mentioning similar problems. They also report mplayer and xawtv working fine. Not sure what else I can say regarding this. I've gone above and beyond to create a credible and detailed report. Should I file a proper bug? Will that get more attention?

Thanks,

Daniel

Again, standard=0 is not what you want (unless your driver can autotune, which it evidently cannot).

After more research, I came upon this:

https://trac.videolan.org/vlc/ticket/10378

My streaming script now works. Here it is:
The fix was to add :chroma=YUYV to the v4l2 section of each input camera.

While it is now evident that this is in fact a driver issue, it was easy for me to discount such an assertion when it worked before. Sorry about that.

Now to get the marquee parts working!

Daniel