Traditionally, video (and film) has always been in landscape orientation - that is, wider than it is high. This is partly due to the way our eyes see the world. Television screens, and most computer screens are landscape oriented. So it's no surprise that video files are encoded by the camera with landscape orientation - usually as 16:9.
The ideal way to shoot video with a smartphone is therefore to hold it lengthwise so that the recorded image is landscape - the video can then be played back full screen on television and computer screens.
However lots of people find it natural to hold their phone upright when recording video, so the image is in portrait orientation. But just like any other video camera, the video is still recorded as landscape, so when it is played back on a television or computer screen the whole image is lying on its side (i.e. rotated by 90 degrees). This isn't a problem if the video is going to be played back on the smartphone as it can just be held upright again to view the picture the correct way up. But it's not really practical to pick up a large television or computer screen and turn it on its side so that the video can be viewed full screen. If portrait video is to be played on a landscape screen or edited into a landscape video project (e.g. for a video DVD), then you will either have to lose the top and bottom of the image, or wide black bars will get added to either side (with a reduction of resolution too). Obviously this isn't ideal, so we would recommend that you always shoot video in landscape orientation on smartphones.
Although smartphones always record in landscape format (even when held in portrait orientation), some such as the iPhone store some advisory "orientation information" in the video file saying that the phone was held upright (i.e. rotated by 90 degrees) when the recording was made.
In the past, the Burn-in Time Stamp and Burn-in Metadata tools of DVMP Pro always wrote the burned-in text (and the burned-in logo image) in landscape orientation. However, if the smartphone had been held in portrait orientation when the recording was made, the text would appear to be written down the side of the image after it had been imported to video editing software and rotated back to portrait orientation.
But now, for MOV and MP4 files, DVMP Pro can check for the presence of the orientation information. If this says that the phone had been help upright during recording, then the whole stamped/burned-in text layer can be rotated by 90 degrees so that the text is written the same way up as the image content. So when you import the burned-in files into video editing/authoring software and rotate it to portrait orientation, the text will be the "correct" way up.
Please note that DVMP Pro's Burn-in tools will only rotate the text layer for MP4 and MOV video files that contain the advisory information. If the information is not present, there is no way of telling which way up the camera/phone was being held during recording, so the video file will be burned-in as landscape.
Because you may be burning-in a mixture of portrait and landscape files, it is important that the burned-in text size and positioning are consistent. The text size and positioning is therefore always calculated based on the landscape shape, and then for portrait files it is rotated by 90 degrees. Because the portrait width is less than the landscape width, any text positioned with high values of X%, after the 90 degree rotation may be truncated against the portrait's right edge (being the landscape top edge before rotation).
Burned-in text layer rotated to Portrait 90 degree CCW orientation
Also any text that was positioned with high values of Y%, after the 90 degree rotation would appear about a third of the way down the portrait image. This isn't ideal, so DVMP Pro applies an adjustment to the text positioning for portrait video. For metadata text items whose Y% value is set to 50% or greater, their position is shifted so that they are justified to the portrait top edge. This means that there is a "Dead Zone" across the middle of the portrait where no text can appear, but that's OK as it's very unlikely that you would want text written across the center of the image.
All of the above also applies to the Custom text item and the logo image (if used).
Please note that when playing video files in the current version of DVMP Pro, it does not actually rotate the image of portrait video - it still plays in landscape orientation.