MP4 File - MediaInfo only shows file size. Encrypted maybe?

[bbabraham]

Hi, I copied a few mp4 files to my PC from my iPhone that had been downloaded by an app. I wanted to make some gifs out of them.

I tried a few players but they wouldn't open. Tried a few video converters - still didn't recognise anything. MediaInfo only shows the file size and no other information.

The video does play in the app on my iPhone but not on my PC. Could it be encrypted or something?

[Baldrick]

Can the app play them? Maybe just some special headers to block copying.

But you could try graus video repair tool and see if it can find any video in the mp4.

[bbabraham]

Yes the app plays them.

Thanks, I'll give it a try.

[bbabraham]

I think you're onto something there.

This is all new to me but Grau found this in the scan:

Entropy scan results
Your complete input file has been analysed in small blocks, and the entropy results show which blocks may contain video data (and which may not). A value less than 0.6 typically means that there is definitively no video data in that block, a value greater than 0.6 means it may contain video data.


start block (KB) - end (KB) -- entropy (must be higher than 0.6 for video data)
--------------------------------------------------------------------------------------------
[NOTICE] entropy 0 - 65536 -- 1
[NOTICE] entropy 65536 - 131072 -- 0.999999
[NOTICE] entropy 131072 - 196608 -- 1
[NOTICE] entropy 196608 - 262144 -- 1
[NOTICE] entropy 262144 - 327680 -- 1
[NOTICE] entropy 327680 - 393216 -- 0.999999
[NOTICE] entropy 393216 - 458752 -- 0.999999
[NOTICE] entropy 458752 - 524288 -- 1
[NOTICE] entropy 524288 - 589824 -- 1
[NOTICE] entropy 589824 - 655360 -- 1
[NOTICE] entropy 655360 - 720896 -- 0.999999
[NOTICE] entropy 720896 - 786432 -- 1
[NOTICE] entropy 786432 - 851968 -- 1
[NOTICE] entropy 851968 - 917504 -- 1
[NOTICE] entropy 917504 - 983040 -- 0.999999

I checked the setting "Reencode repaired movie files" and left everything else default. It created a truncated mp4 file but this new file still doesn't open in any video players or converters. Grau's built in "preview" also didn't play anything. It just says "please wait" very briefly and then "finsihed" without actually opening or showing any video. The file is also only 4MB whereas the original is over 900MB.

I randomly played around with the other options but nothing came of it - not that I know what the options mean.

But the above entropy shows that there is video in there right?

[Baldrick]

Maybe you can open the video in an hex editor and try remove some "crap" at the start. Then try run it in grau.

Or maybe it uses a more complex encryption...then can't you do much.

[DB83]

Possible that the ap that downloads the video to the iphone creates a drm licence on the phone.

Without the licence, the video can not play. You cam always Google regards that ap and PC transfer but probably little chance of success.

[bbabraham]

Maybe you can open the video in an hex editor and try remove some "crap" at the start. Then try run it in grau.

Or maybe it uses a more complex encryption...then can't you do much.

Thanks. I've never done this but I'll see what I can find with Google.

[bbabraham]

Possible that the ap that downloads the video to the iphone creates a drm licence on the phone.

Without the licence, the video can not play. You cam always Google regards that ap and PC transfer but probably little chance of success.

Thanks. I'll give this a try too. I had searched before but maybe including "drm" in my search will help.

[bbabraham]

I found a couple mentions in forums of people trying to view videos from this app on their PC. No solutions though. One guy mentioned the videos having DRM/encryption but it looked like an assumption on his part.

I haven't had a chance to research hex editing yet.