OT: Timestamp data in MOV (QT) files?

terrypin wrote on 6/27/2014, 9:06 AM

I've posted this in a photography forum too, but maybe others here have some thoughts please?

I like to rename my photos and movie clips so that filenames clearly show the timestamp. I don't usually have problems with my JPG stills. But movie clips have started causing me some confusion and I'd appreciate any clarification others can offer please.

Up until recently all my photos and video clips have been taken on my Canon Ixus 220 HS; JPG and MOV (QT) files respectively. I usually rename these correctly in Bulk Rename Utility (BRU), including the videos.

So for example this test clip MVI_6670.MOV, taken with the Canon at about 13:20 UK BST, has been renamed to 20140627-132106.MOV. BRU is set to use 'Modified (Curr)', with an 'Offset' of +1. (I have to remember to change that on the appropriate dates.)

MediaInfo reports this:
https://dl.dropboxusercontent.com/u/4019461/CanonMOVinMediaInfo.jpg
(10 lines of info)

All fine so far.

But recently I've started to use my iPad for a few of my clips and that's thrown a spoke in the works.

For example IMG_1404.MOV taken at about 14:20 UK BST is shown by BRU (using the setting I use for my Canon MOVs) as 20140627-154109.MOV, which appears to be the standard 'Modified' date plus 1, so useless. Nor do any of the other BRU settings work.
https://dl.dropboxusercontent.com/u/4019461/iPadMOVinBRU.jpg

MediaInfo reports this:
https://dl.dropboxusercontent.com/u/4019461/iPadMOVinMediaInfo.jpg
(10 lines of info)

Given that both Canon and iPad file formats are QT in an MOV container, am I right therefore in concluding that it is the camera that determines what timestamp data gets written? No consistent standard on which I can rely?

--
Terry, East Grinstead, UK

Comments

johnebaker wrote on 6/27/2014, 2:00 PM

Hi Terry

I think this may answer your question:-

I think this may be due to a difference between FAT and NTFS filing systems and time.

The FAT file system, as used in Memory cards, writes the timestamp using local time. So if it's 11.00 AM when you take a picture then it's "11.00 AM" that gets written to the memory card.

In NTFS, all timestamps are written in Coordinated Universal Time or UTC (~ GMT). If it is 11.00AM, and you're in the Europe which is UTC +1, then the actual time written to the disk is 10.00 UTC. When the file's time is displayed, then of course, the time zone is corrected for and the time of 11.00AM is shown.

If your camera is set to auto adjust for daylight saving and / or local time becomes even more complicated.

Auto local time is often associated with a camera that has GPS built in eg my Sony camera does this and occassionaly cause havoc if I use the GPS during part of a holiday if try to order the shoots by date/time.

. . . . For example IMG_1404.MOV taken at about 14:20 UK BST is shown by BRU (using the setting I use for my Canon MOVs) as 20140627-154109.MOV, which appears to be the standard 'Modified' date plus 1, so useless. Nor do any of the other BRU settings work. . . . .

The camera has recorded the 'local time', ie the cameras time setting, to the image on a FAT formatted card. Once brought in to the compuer the file system is using NTFS so 1 hour gets added on - outside of daylight saving hours the correct date/time should be displayed.

HTH

John

terrypin wrote on 6/27/2014, 4:00 PM

Hi John,

Thanks, but I'm going to have to ponder on that for a while and do a few more experiments to clearly grasp this! But I sure do agree it gets complicated. Like you, I try to get my family video scenes reasonably faithful to real local time. (Occasional exceptions excused for artistic purposes!) but I've never had any great problem with working out the time stamps from my Canon (which does use an SD card). It's my iPad that's thrown me. I'm going to make sure I take photos and 1 second videos of my wrist watch more consistently.

Here's another take I just received on it from the videohelp forum which confirms my suspicion that the cameras make their own rules:

Correct. Actually, it is the writing app/firmware. There are "standards" but there are enough of them that YMMV.

Some cams record Timecode (smpte/ebu or otherwise), some record a starting "timestamp" (both as metadata tracks/streams SEPARATE from V+A), some use the container created start stamp, some the container modified start stamp, some use an ENDING stamp. Some don't really do any at all (though they may include this info in other areas, as in the case of some AVCHD clips which keep that in the CLIP List info).

Figure out how it works for a particular cam, and follow that protocol when using footage from that cam, then follow different rules for different cams. Maybe even do it manually.

Sorry, that's the way it goes...

johnebaker wrote on 6/27/2014, 5:09 PM

Hi Terry

. . . . Some cams record Timecode (smpte/ebu or otherwise), some record a starting "timestamp" (both as metadata tracks/streams SEPARATE from V+A), some use the container created start stamp, some the container modified start stamp, some use an ENDING stamp. Some don't really do any at all (though they may include this info in other areas, as in the case of some AVCHD clips which keep that in the CLIP List info). . . . .

IIRC we had a similar discussion on this some time ago re which timestamp MEP reads Created or Modified.

. . . . I'm going to have to ponder on that for a while . . . .

In a nutshell:

- the camera will timestamp the file with its current time - Created or Modified depends on the camera.

- the computer reads the timestamps and then corrects for BST and Time zone.

John

terrypin wrote on 6/28/2014, 2:23 AM

Hi John,

- the camera will timestamp the file with its current time - Created or Modified depends on the camera.

But it appears that isn't the full picture. Some cams apparently add the zone at the same time. Presumably my iPad added +2:00 to the MOV file based on its GPS data. How else would it know I was in Belgium? Also, what meaning could the term 'modified' have inside a cam?

- the computer reads the timestamps and then corrects for BST and Time zone.

Not sure I follow that. I'm sure you don't mean it literally, i.e. that for example the PC rewrites the JPG or MOV when I import those SD card files? Of course, various programs do their own thing with the data, sometimes misleadingly.

Bottom line still seems to be that the only foolproof way to ensure you get the correct local time is to get your watch into the picture frequently!

--------

Anyone else using an iPad for source material?

Terry, East Grinstead, UK

johnebaker wrote on 6/28/2014, 3:30 AM

Hi Terry

. . . .Presumably my iPad added +2:00 to the MOV file based on its GPS data. . . . .

That it what I said in my first post

. . . . If your camera is set to auto adjust for daylight saving and / or local time becomes even more complicated Auto local time is often associated with a camera that has GPS built in eg my Sony camera does this and occassionaly cause havoc if I use the GPS during part of a holiday if try to order the shoots by date/time.. . . .

It does get messy because devices / software do not use the same timestamp for reading the file dates.

Cheers

John