I've been asked to try and get some footage from a security camera working. Now, this is not my normal area of expertise, so, while I've had an interesting day off tinkering, I thought I'd ask for advice from people who deal with this kind of thing more often.
I have a file of 14,671,754 bytes size, hotspot.mp4
After some basic investigation I found that there were none of the expected headers of an mp4 file, so, as the file looked to be opening on data, I spliced in a header from another mp4 file using a hex editor and saved the result back to hotspot_fudge.mp4 and went looking for mp4 fix utilities. Now, I've only tried a couple, for example File Repair 188.8.131.52 and Video Repair Software from Grau GmbH, but they have have been completely unsuccessful; not surprising really, as I don't even know if the header details I hacked in are compatible.
The spliced file provides a thumbnail of its content as an icon which matches the expectation of the view from a security camera and opening the it in Windows Movie Maker shows thumbnails as well. If the clip is played, all that displays is a green strip covering about the bottom 1/12th of the screen. There is the odd crackle on the audio at the start of the clip; to be honest, I don't know if there's an audio channel available, although I doubt it as this is security-cam material.
The slight crackle and the blown picture suggests to me I'm reading the 'wrong' data, but the thumbnails give me hope.
Do I have a hope in hell of getting this thing running by this method?
Can anybody suggest something easier and better and, naturally, at no cost (other than time, of course)?
If it is feasible to get the file moving, can anybody suggest which header parameters I should be modifying and what sort of values I should be aiming for?
And is there a way of working out how long the file should play for, based on its byte-size? I have a basic value of 4m 18s in at the moment, which is simply the length of the mp4 video I borrowed the substitute header off in the first place?
I hope I haven't just caused a forumful of folk to start laughing at naive ambitiousness of this...
All the best
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Last edited by QuinB; 28th Feb 2015 at 14:49.
Usually there is a conversion software and/or viewing software +/- a software decoder included with the equipment - have you tried that?
Patching in a header or modifying with a hex editor usually won't work for these, and it does play it will usually be damaged
Sorry to say, all I have is a file, all I've tried I've told.
I have been offered no access to the hardware, I don't know what it is, I don't know what software might be available. That's the problem with being a techie - mates want free support.
I might be able to get a site visit sorted out, but that's a 'might'. Can you give any more detail of the sort of thing I should be looking for? I can wing these things, but it's nice to have a bit of background.
Damaged footage would be bad as this stuff might have to be used as evidence. Not necessarily at a court level, but enough to establish an identity.
However, it's a real education and there's nothing like getting your hands dirty to learn the real ins and outs of a new area.
If you have the model#, or the company name that makes the device - you can do a better search for the proper software . Some security devices have encrypted recordings on top of the header issues. So do all you can to find out more information
If you want to upload the clip ,since it's fairly small, there might be someone able to hack it or get it working here
Well, here y'go.
One headerless file, one fudged; with thanks to anybody stepping up and taking a swing at the problem - that's how I got into this one, after all!
How is it that you can see thumbnails of the content in the of the fudged file?
I still have catchup reading on the MP4 standard to get through; it's not exactly fast-fix friendly, is it?
You should upload the unpatched original
"Anything for a weird life!"
I''ll see what I can do. Thanks for the suggestion.
@poisondeathray - it's attached on the next post. Had a minor issue and the upload canned without me noticing before posting.
HAHA . I saw the "crime"
There was a doggie taking a poop, and the owner didn't scoop it up .
FFmpeg to treat the input file as H.264 material. The -codec option says no transcoding; just copy the stream to output. FFmpeg guesses the container format from the extension of the output filename. Now, let's hope catching the perp will be so easy!
Not a civil court problem, but the dog wardens will be interested and the town councillor who begged the favour will be over the moon.
£1000 fine ?! wow steep. It varies in Canada, but most places are only $50-200. Not a huge deterrent
The problem with that shot is there is no direct view of the actual poop . You can only infer that something was left there, but the view is obscured. It wouldn't hold up to any legal scrutiny. Well placed, and "aimed" indeed
Your town councillor has probably already done this, but he should approach other shops in the area who might have other recordings or views.
Just a rant now: if someone is going to invest in an actual security camera system etc... not a prop for deterrent - they are better off getting a decent one that has some resolution to it . Even if the perp walked right in and put his face to the camera , you could barely make out any details. Even the ancient old analog recording tape systems would be better than this setup