[lug] Video recording with continuous playback

Wed Mar 7 13:46:31 MST 2018

I second the idea of just saving to disk and starting playback 60 seconds later. There may be some video formats which have to complete before they run, but there are some in which you can start playback prior to ending the current recording (I don't know a lot about those formats, but I know both exist).

About streaming: It uses a lot of bandwidth, and an ordinary laptop hard drive may not be fast enough depending on format and quality chosen. An SSD would typically be faster and make life easier for you in this case (sorry, implies more cost).

You haven't said much about the use-case for how you see the 60 second delay being used so it would be difficult to say more than just waiting 60 seconds and starting playback (provided the video format works this way). If you were just saving in RAM you might need a very expensive tablet or laptop due to the amount of RAM required. Consider uncompressed video with 3-bytes of video (24-bit) and an alpha channel (transparency), or 4 bytes per pixel and 1920x1080 resolution at 30 fps for 60 seconds and converted approximately to GB:
(4*1920*1080*30*60)/(1024*1024*1024) = 13.9 GB

Many applications can be made to use hardware encoding/decoding present in the video card. Those which support H.265 would be superior to those which support only H.264.

You probably need to add more specific details about what you are going to do, e.g., whether simply starting playback 60 seconds in is ok, what resolution you need, what frame rate you need, how long a recording will be (indirectly implies disk size), so on.

----- Original Message -----From: Steve Sullivan <steve.sullivan at mathcom.com>To: Boulder (Colorado) Linux Users Group -- General Mailing List <lug at lug.boulder.co.us>Sent: Wed, 07 Mar 2018 14:36:50 -0000 (UTC)Subject: Re: [lug] Video recording with continuous playback

Thanks for the comments!

I'm a novice at video so probably my question wasn't clear.What I'm looking for is, all within a single small Linux laptop:

* Camera, such as USB camera or tablet internal camera. Logitech C920 was recommended -- USB connected would be fine.

* Software to continuously buffer the video stream, adding 60 seconds delay.

* Playback, to continuously display the delayed stream on the tablet's screen. VLC?

So what you see on the screen is whatever the camera saw 60 seconds ago.Almost certainly we won't have any network access.

Do you have recommendations on how to do the video buffering,or what small laptop might be appropriate?

Many thanks,

Steve

On Wed, Mar 07, 2018 at 12:57:19AM -0700, Bear Giles wrote:> No networking? Then I guess transmitting a signal to a transceiver 30> light-seconds out wouldn't work either.> > On Tue, Mar 6, 2018 at 4:59 PM, <stimits at comcast.net> wrote:> > > You might find a USB webcam using the standard "USB Video Class" is a very> > simple solution if you don't mind adding a USB camera (e.g., the Logitech> > C920). So long as it doesn't take a custom driver you could install (and> > capture) with "guvcview". There are other applications which can work with> > USB standard cameras, this particular one is easy and reliable. I suspect> > there would be no issue getting the application to work with all kinds of> > smaller/mobile devices if they run Linux.> >> > ----- Original Message -----> > From: Steve Sullivan <steve.sullivan at mathcom.com>> > To: lug at lug.boulder.co.us> > Sent: Tue, 06 Mar 2018 22:17:40 -0000 (UTC)> > Subject: [lug] Video recording with continuous playback> >> > Hi, I want to put a cheap netbook / chromebook / ipad / whatever> > on a tripod recording divers on a team at the swimming pool.> > There'd be simultaneous playback, delayed about 60 seconds later.> > That way the divers could hop out of the pool and see what> > they've just done.> > There are apps that do this for phones, like> > https://itunes.apple.com/us/app/bam-video-delay-for-coaching-and-personal-> > training/id517673842?mt=8> > https://chrome.google.com/webstore/detail/replay-it-sports-video-de/> > dcdhimjnicocbcjhmfcjlooncidccanl?hl=en> > Then I thought, why not Linux? Does anyone have experience> > with this? What hardware and software would you recommend?> > Many thanks,> > Steve> > --> > ========================================> > Steve Sullivan steve.sullivan at mathcom.com> > 720-587-7498 <(720)%20587-7498> http://www.mathcom.com> > ========================================> > _______________________________________________> > Web Page: http://lug.boulder.co.us> > Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug> > Join us on IRC: irc.hackingsociety.org port=6667 channel=#hackingsociety> >> > _______________________________________________> > Web Page: http://lug.boulder.co.us> > Mailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lug> > Join us on IRC: irc.hackingsociety.org port=6667 channel=#hackingsociety> >

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========================================Steve Sullivan steve.sullivan at mathcom.com720-587-7498 http://www.mathcom.com========================================_______________________________________________Web Page: http://lug.boulder.co.usMailing List: http://lists.lug.boulder.co.us/mailman/listinfo/lugJoin us on IRC: irc.hackingsociety.org port=6667 channel=#hackingsociety
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