[lug] Video recording with continuous playback

Wed Mar 7 14:17:54 MST 2018

I wonder if something like zoneminder with record on motion would work?  It
wouldn't necessarily do the buffered playback but might offer a timeline of
recorded videos that would be easy enough to navigate?  (You could then
automate dumping older video as it's no longer needed, etc.)

My $0.02

On Wed, Mar 7, 2018 at 1:46 PM, <stimits at comcast.net> wrote:

> 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> <(720)%20587-7498>
> http://www.mathcom.com
> > > ========================================
> > > _______________________________________________
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> --
> ========================================
> Steve Sullivan steve.sullivan at mathcom.com
> 720-587-7498 <(720)%20587-7498> http://www.mathcom.com
> ========================================
> _______________________________________________
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