Subsurface media import problems

[Robert Helling]

Enric,

> On 5. Sep 2020, at 19:20, Dirk Hohndel via subsurface <subsurface at subsurface-divelog.org> wrote:
> 
> Robert,
> 
> I assume you might be the better person to respond to this one...
> 
> /D
> 
> On September 5, 2020 1:57:37 AM PDT, Eric Tanguy <erictanguy2 at orange.fr> wrote:
> Hi, i have some problems importing png and mp4 medias.
> 
> With png, i think there is a location time problem. When i try to import a png media in subsurface it finds that the dive time is GMT whereas the dive time imported is Paris Time so there is 2 hours of difference. So why the importing dive time is considered as GMT ? Maybe it's why i can't achieve anymore the GPS synchonization with subsurface-mobile
> 
> With mp4 files, i have another problem. I use attribute changer to modifiy created time, modified time and accessed time but subsurface seems to read date and time in other place i can't achieve to find and change ...
> 
> Thanks
> 
> Best regards
> 
> Eric
> 

First of all: Time zones are difficult. In Subsurface we decided that all times are local times and we explicitly don’t keep a time zone (as that would create problems like: On a vacation, your are in some time zone and start a dive at 9 a.m., say. Then you return home and change to your local time zone and it would look like your dive started in the middle of the night). But you are correct, this can create problems when importing date/time from other sources that come with time zone information like importing media. When thus forced to say which time zone the internal Subsurface time corresponds to, we use UTC lacking anything better.

To avoid the problems you describe, the media import dialog through which you add media files to dives offers you the possibility to apply a time shift. Simply set that to one or two hours (depending if you are in daylight saving time or not) should solve this for you. If you don’t want to do the mental math, there is even the possibility to take a picture of your dive computer showing what it thinks the time is and Subsurface will do the math for you. This also removes problems stemming from your dive computer and your camera not having exactly synched clocks. All this is described in section 4.5 of the Subsurface user manual.

As you found out, we don’t use the time stamp of the image files but rather the time that is in the EXIF data of the media file. If you really want to change that you should use an exif-editor.

Hope that helps.

Robert

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