[LAU] live video switching? WAS: Re: VJ / VeeJing software alternatives

[Robin Gareus]

On 07/21/2014 06:33 AM, Len Ovens wrote:
> On Sat, 19 Jul 2014, Robin Gareus wrote:
> 
>> http://dvswitch.alioth.debian.org/wiki/
>>
>> Can switch a couple of camera (DV) sources and is OSC remote
>> controllable (the website is a tad out of date, but the source rocks)
> 
> I thought I would try it out...
> 
> There is also a dvsource-v4l2-dv for USB devices... Hmm, I have a Canon
> eos 60d which will record nice videos that I can download and edit with
> any sw... I can tether it with entangle and use that to fully control
> the camera from my desktop, in preview mode I can see the live video
> from the camera on my screen... but get it to show up as /dev/video* ?
> not a chance.
> dmesg shows:
> [17678.621172] usb 3-7: new high-speed USB device number 8 using xhci_hcd
> [17678.634428] usb 3-7: New USB device found, idVendor=04a9, idProduct=3215
> [17678.634437] usb 3-7: New USB device strings: Mfr=1, Product=2,
> SerialNumber=0
> [17678.634442] usb 3-7: Product: Canon Digital Camera
> [17678.634446] usb 3-7: Manufacturer: Canon Inc.

Hi Len,

That's just the usb stack detecting a device and reading the IDs. It
does not load a driver to handle it.

> Anything I can find suggests using a screen reader to get the live video
> into the computer. 

screen reader? that sounds odd. A Video-Loopback can work:
http://chdk.setepontos.com/index.php?topic=4672.0 suggests

$ sudo modprobe vloopback
$ V4L_DEVNAME=/dev/video0 canon-capture
capture> start
capture> v4l on

It looks like the canon camera is not supported by the v4l2 driver.

> (even for windows or mac) 

The built-in webcam on a macbook (running Linux) works OOTB with
dvsource-v4l2-dv as does a cheap external USB webcam that I have (which
just shows up as /dev/video) both also produce audio-feeds.

For the real-thing(TM) I use firewire and camcorders or cameras.

> Sounds silly. Am I missing something? There is no audio that way.

Use a proper microphone, soundcard and `dvsource-jack` :)

Though in our case we ended up using the audio from the first camera:

    Mics -> mixing-desk -> XLR -> camera 1 in.

That way the audio was always in sync (thanks for firewire
iso-synchroneous streams). dvsource-jack has options to calibrate
latency, and align the A/V but it may drift when streaming over long
periods of time if the soundcard is not word-clock synced with the camera.


HTH,
robin

PS. For testing dvsource-file comes in handy for testing.