Text on ffmpeg

[Willem Ferguson]

---------- Forwarded message ---------
Date: Tue, 11 Sep 2018, 22:37
Subject: Text on ffmpeg
Hi Willem,
---
Video-Thumbnails
By default, videos are shown on the profile and the _Media_ tab with a
placeholder-image.
To extract real thumbnails from videos, _Subsurface_ relies on the
external _FFmpeg_ software.
This software can be downloaded from
link:https://www.ffmpeg.org/download.html[FFmpeg
<https://www.ffmpeg.org/download.html%5BFFmpeg> download page].
Most Linux distributions ship with an _FFmpeg_ package and therefore
do not need an additional download.
1) On Windows, put the _ffmpeg.exe_ file in the directory containing
the _Subsurface_ executable.
On Mac and Linux, make sure the _ffmpeg_ command is in the path. This
should be the case for
_ffmpeg_ installed from official packages.
2) In the _General_ tab of the _Preferences_, choose the path to the
executable.
To enable thumbnail extraction from videos, check the _Extract video
thumbnails_ box
in the _General_ tab of the _Preferences_. If _Subsurface_ fails to
load the _FFmpeg_ executable,
this option will be turned off. Re-enable it after succesfully
installing _FFmpeg_.
In the _General_ tab of the _Preferences_, you can also choose the
position in the video where _Subsurface_
should try to extract the thumbnail. The left-most and right-most
positions of the _Extract at position_
slider signify the beginning and the end of the video, respectively.
Note that if _Subsurface_ cannot
determine the length of the video (this can be the case for AVI
files), the first frame
of the video will be extracted.
---
Is this kind of text useful for you? Should I make screenshots?
Thanks,
Berthold

Hallo Berthold,

Looks like our normal email is working again. Thanks for the above. That
is certainly very useful and I tested it on my Linux box. One question.
The date/time that is used to insert the video: are there any Exif or
equivalent data in the file from which this is obtained, or does it use
the file system date/time? My video viewer does not produce any
date/time incoded in the ,mp4 itself.

Second question. I have several .MOV files in the same directory as the
.mp4 file that I work with. When, in Subsurface, I select "Attach images
from file" and I point it to the right directory, and select "Video
files" it only sees the .mp4 file, NOT the .MOV files. The file filter
that determines which files are seen must be set by the Subsurface
importer. However, when I select the "All files" filter, then it sees
the .MOV files. So, it appears the filter for "Video files" could be
improved to include the formats that ffmpeg supports????

Thirdly, it is a rudimentary issue to update the dive list context menu
entry to read "Load Images from file" to "Load media from file". The
same should probably happen to the menu entry immediately underneath
"Load images from web". Should I do that?

Kind regards,

willem

Kind regards,

willem

[Berthold Stoeger]

Hi Willem,

Post by Willem Ferguson
The date/time that is used to insert the video: are there any Exif or
equivalent data in the file from which this is obtained, or does it use
the file system date/time? My video viewer does not produce any
date/time incoded in the ,mp4 itself.

Yes, we try to extract meta-data from the mp4. If that doesn't work, we take
the timestamp from the file. To my knowledge, AVI has no standard way of
recording the timestamp as metadata.

If you have videos where we don't properly extract the date, it would be great
if I could have a look at them to improve our routines.

Post by Willem Ferguson
Second question. I have several .MOV files in the same directory as the
.mp4 file that I work with. When, in Subsurface, I select "Attach images
from file" and I point it to the right directory, and select "Video
files" it only sees the .mp4 file, NOT the .MOV files.

That's strange. I also have a directory with .MOV and .mp4 files and both are
shown. The list is in core/qthelper.cpp (videoExtensionList). The only thing
that I note is that it is not sorted alphabetically, but that shouldn't
matter..?

Post by Willem Ferguson
Thirdly, it is a rudimentary issue to update the dive list context menu
entry to read "Load Images from file" to "Load media from file". The
same should probably happen to the menu entry immediately underneath
"Load images from web". Should I do that?

Sure, if you have time, go ahead. :)

Berthold

[Willem Ferguson]

Post by Berthold Stoeger
Hi Wi
Sure, if you have time, go ahead. :)
Berthold

Berthold,

When looking for the date/time of a video file, which EXIF attribute is
used to get the time? Is it a UCT value?

I am messing with exiftool to alter some videos to have date/times that
coincide with a dive in order to see the way the video is shown on the
profile.

Kind regards,

willem

[Berthold Stoeger]

Hi Willem,

Post by Willem Ferguson
When looking for the date/time of a video file, which EXIF attribute is
used to get the time? Is it a UCT value?

To my knowledge Quicktime (mp4, mov, etc.) doesn't have EXIF in that sense. It
consists of "atoms" (which amazingly can contain other atoms - no kidding) and
we search for the "mdhd" (=media header) atom, from which we extract the
timestamp and the duration. The timestamp is supposed to be in UTC (as seconds
since 1.1.1904 - Apple time).

You *can* incorporate XMP data (https://de.wikipedia.org/wiki/
Extensible_Metadata_Platform) into such a file. If there is interest, I can
have a look at how much work it would be to extract useful information from
that. Since Qt has an, albeit dog-slow, XML parser it shouldn't be too hard.

For WMV files we use the "file properties object" in a similar way.

Not sure if these details answer your question...?

Post by Willem Ferguson
I am messing with exiftool to alter some videos to have date/times that
coincide with a dive in order to see the way the video is shown on the
profile.

Which option do you use to modify the date? I'll try to see what it does.

Berthold