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Not video switching, and if all your video sources are going to be consumer products it may be of no interest to you, but the BBC has done a fair amount of research and development into tapeless production on Linux over the years. Mainly multi-channel recording, using prosumer Blackmagic card giving up to 4x SD in/outs. http://ingex.sourceforge.net/ Plus other stuff, some of which is online but not targeted for the general public, where BBC News is using Ubuntu boxes and the Blackmagic cards for recording archive. Quite a lot of house written software though and seems even the Blackmagic driver is their own... Actually they used them for the Olympics so some info in an article here: http://www.bbc.co.uk/blogs/internet/posts/Raven-File-Ingest-Olympics (There is a Wiki out there with a lot more technical info though ;) ) > Date: Mon, 21 Jul 2014 17:46:20 -0700 > From: len@xxxxxxxxxxxxx > To: robin@xxxxxxxxxx > CC: linux-audio-user@xxxxxxxxxxxxxxxxxxxx > Subject: Re: live video switching? WAS: Re: VJ / VeeJing software alternatives > > On Mon, 21 Jul 2014, Robin Gareus wrote: > > > On 07/21/2014 06:33 AM, Len Ovens wrote: > >> [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. > > > > That's just the usb stack detecting a device and reading the IDs. It > > does not load a driver to handle it. > > That was my point ... no driver. It doesn't advertise itself as a video > device. That is the problem, the camera can do a number of things and look > to the computer like a USB drive, ptp camera or something else. So there > needs to be something other than v4l to deal with it... something that has > enough user input to tell it that "right now I want to use this as a > <whatever>." There is no way of knowing when the user plugs it into the > USB port what they want to do. The computer assumes download pictures. > > >> 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 > > That is meant for DV. I don't have that. (I also don't seem to have the > vloopback) The Camaras come with tethering SW and I can use entangle in > Linux for the same thing. They all offer a preview mode which is video. > The idea is to screen capture that part of the screen and feed it to > video. It seems most of these things want to use an older kernel... that > is they have not been maintained for some time. I get the idea that in > times past a DV/firewire interface was the chosen method of connecting a > camera to the computer. But the latest batch of cameras are now all USB2.0 > because everyone has them. Video streaming does not seem to be something > that is easy to set up... not something Canon intends these DSLRs to be > used for, so there seems to be know way of setting them up to connect to > the computer as a "webcam". > > > It looks like the canon camera is not supported by the v4l2 driver. > > I think it is the camera that does not set itself up the right way. > Preview mode creates video in any case. I do not know what the latency is > internal to the camera itself, but the whole chain from camera sensor to > screen in preview seems about 1/3 sec. > > > 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. > > There will be drift anyway with more than one camera, but if dvswitch > starts frame grabbing fresh with each switch action it will remain very > close. Add a bit of delay to the audio and the brain will sort things out > just fine. It seems obvious to me that the video sources are synced using > frame store techniques in DVswitch as memory is cheaper than extra cables > and master sync generators. (and cameras with external sync in) > > -- > Len Ovens > www.ovenwerks.net > > _______________________________________________ > Linux-audio-user mailing list > Linux-audio-user@xxxxxxxxxxxxxxxxxxxx > http://lists.linuxaudio.org/listinfo/linux-audio-user |
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