Since MP4 video files require a date and time and if a date and time is not set, it will set itself to 0000:00:00 00:00:00. Now 0000:00:00 00:00:00 is not a valid date since the months are between 01-12 and the days are between 01-31 and when it returns 0000:00:00 00:00:00, 00 is not a valid month or day number. This is how ExifTools returns data on MP4 files which "Do not have a date and time" metadata
For GPS data, will exiftool return an altitude of 0 if altitude is not set. I ask this since 00 is not a valid day or month and when I use this command either of these commands below in ffmpeg to recreate a video, exiftools will return an altitude of 0. However when I use ffprobe to read the output files using each command, the one were no altitude was set does not return an altitude value while the one with an altitude does return an altitude of 70.
Without Altitude
ffmpeg -i "input1.mp4" -vcodec copy -acodec copy -metadata location="39.1234 -48.1234" "output1.mp4"
ffprobe output1.mp4
location : +39.1234-048.1234/
exiftool output1.mp4
GPS Altitude : 0 m
With Altitude
ffmpeg -i "input.mp4" -vcodec copy -acodec copy -metadata location="39.1234 -48.1234 70" "output2.mp4"
ffprobe output2.mp4
location : +39.1234-048.1234+70.000000/
exiftool output2.mp4
GPS Altitude : 70 m
Quote from: trymeout on May 11, 2021, 10:58:24 PM
For GPS data, will exiftool return an altitude of 0 if altitude is not set.
ExifTool should never return 0 for a tag if it doesn't exist.
What is the value of the GPSCoordinates tag?
- Phil
Exiftool returning 0 altitude because of the LocationInformation tag exists and you said (https://exiftool.org/forum/index.php?topic=12464.msg67434#msg67434), best that can be done is setting it to 0. trymeout is ignoring the previous1 (https://exiftool.org/forum/index.php?topic=12442.msg67309#msg67309) posts2 (https://exiftool.org/forum/index.php?topic=12464.msg67419#msg67419) about where it is located.
Edit: Also, it should be noted that the GPSAltitude in this case is going to be the Composite:GPSAltitude tag, which exists only in exiftool. I don't believe the LocationInformation tag has much software support.