Read/write video files' metadata using QtAV/ffmpeg

[Gilles Caulier]

Hi,

I respond late to this file, but i respond : with this kind of simple C
source code :

https://ffmpeg.org/doxygen/0.7/metadata-example_8c-source.html

... i can obtain these info from a MP4 file :

[gilles at localhost GIT]$ gcc ffmetadata.c -lavformat -lavutil
[gilles at localhost GIT]$
[gilles at localhost GIT]$ ./a.out VID_20161224_201626.mp4
major_brand=mp42
minor_version=0
compatible_brands=isommp42
creation_time=2016-12-25T04:16:26.000000Z
location=+37.7536-122.4330/
location-eng=+37.7536-122.4330/
com.android.version=7.0
com.android.capture.fps=30.000000

Exiftool report more information of course :

[gilles at localhost GIT]$ exiftool VID_20161224_201626.mp4
ExifTool Version Number         : 10.45
File Name                       : VID_20161224_201626.mp4
Directory                       : .
File Size                       : 12 MB
File Modification Date/Time     : 2017:01:10 00:05:56+01:00
File Access Date/Time           : 2018:02:26 09:56:28+01:00
File Inode Change Date/Time     : 2018:02:26 09:56:24+01:00
File Permissions                : rw-rw-r--
File Type                       : MP4
File Type Extension             : mp4
MIME Type                       : video/mp4
Major Brand                     : MP4 v2 [ISO 14496-14]
Minor Version                   : 0.0.0
Compatible Brands               : isom, mp42
Movie Header Version            : 0
Create Date                     : 2016:12:25 04:16:26
Modify Date                     : 2016:12:25 04:16:26
Time Scale                      : 1000
Duration                        : 5.80 s
Preferred Rate                  : 1
Preferred Volume                : 100.00%
Preview Time                    : 0 s
Preview Duration                : 0 s
Poster Time                     : 0 s
Selection Time                  : 0 s
Selection Duration              : 0 s
Current Time                    : 0 s
Next Track ID                   : 3
GPS Coordinates                 : 37 deg 45' 12.96" N, 122 deg 25' 58.80" W
Com Android Version             : 7.0
Com Android Capture Fps         : 30
Track Header Version            : 0
Track Create Date               : 2016:12:25 04:16:26
Track Modify Date               : 2016:12:25 04:16:26
Track ID                        : 1
Track Duration                  : 5.67 s
Track Layer                     : 0
Track Volume                    : 0.00%
Image Width                     : 1920
Image Height                    : 1080
Graphics Mode                   : srcCopy
Op Color                        : 0 0 0
Compressor ID                   : avc1
Source Image Width              : 1920
Source Image Height             : 1080
X Resolution                    : 72
Y Resolution                    : 72
Bit Depth                       : 24
Pixel Aspect Ratio              : 65536:65536
Color Representation            : nclx 1 1 1
Video Frame Rate                : 29.824
Matrix Structure                : 1 0 0 0 1 0 0 0 1
Media Header Version            : 0
Media Create Date               : 2016:12:25 04:16:26
Media Modify Date               : 2016:12:25 04:16:26
Media Time Scale                : 48000
Media Duration                  : 5.80 s
Handler Type                    : Audio Track
Handler Description             : SoundHandle
Balance                         : 0
Audio Format                    : mp4a
Audio Channels                  : 1
Audio Bits Per Sample           : 16
Audio Sample Rate               : 48000
Movie Data Size                 : 12008560
Movie Data Offset               : 405243
Avg Bitrate                     : 16.6 Mbps
GPS Latitude                    : 37 deg 45' 12.96" N
GPS Longitude                   : 122 deg 25' 58.80" W
Image Size                      : 1920x1080
Megapixels                      : 2.1
Rotation                        : 180
GPS Position                    : 37 deg 45' 12.96" N, 122 deg 25' 58.80" W

... but at least the minimum are there, as date, GPS info, frame per
seconds.

Certainly more details can be captured with more code as libav API is huge.

So my conclusion is : yes, we can use libav (ffmpeg) to handle some
important metadata from video files.
I cannot guaranty that all video format are supported weel to extract
metadata homogeneous.
I must also check how libav work to extract metadata without any decoding
video file (the expected way to process), to prevent huge time latency
while scanning.

For this purpose, i propose to introduce this kind of code in 6.0.0 branch,
not in 5.x, as next and last 5.9.0 release will be published in few days.

Gilles Caulier




2018-01-11 16:32 GMT+01:00 Andrey Goreev <aegoreev at gmail.com>:

> Hello,
>
> Looks like as long as libavformat/avformat.h presented in the appimage
> digiKam can read/write video files' metadata via calling the library
> directly from c++.
>
> Here is an example: https://stackoverflow.com/questions/45050177/adding-
> metadata-informations-with-ffmpeg
>
> Also looks like ffmpeg is capable of writing whatever tag you want in the
> mdta atom:
> http://www.ffmpeg-archive.org/Write-QuickTime-tags-td4680508.html
>
> Can this help closing the gap left by exiv2 ?
>
> Best regards,
> Andrey
>
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