I'm posting to this thread because I think it refers most closely to what I am asking about.
I thought I was attempting to do something fairly simple when I began a project by extracting and working on separate groups of videos to obtain training images. I worked on the first group, extracting, sorting, culling and manually checking landmarks, then did the same with other groups, ending up with 6 groups. So I had original frames in Group1.mp4, Group1_alignments.fsa, the Group1 folder held the final images, and so on. All was well, and the idea was to then merge all of the alignment files together.
The problem was that I could no longer check on status of the final landmark alignments, because frames were in multiple MP4 files. I've had problems in the past with missing training faces, or (worse) alignments reverting to their original, often horrible landmarks because of some process error on my part. I wouldn't find out about these until watching training and seeing horribly disfigured faces. So I cycle through my entire final training set and confirm that all landmarks were good.
I tried combining all of the videos into one file using MP4Join, and pointing to the merged alignment file, but it found no alignments. I'm assuming because hashes/names no longer matched? I also tried using ffmpeg to write all of the frames to a folder (ffmpeg -i Group1.mpg c:\temp\Group1_%06d.png), which wrote the images out as "Group1_000001.png", etc. At this point, I lowered my troubleshooting expectations by running Manual using only a single group (Group1_alignments.fsa, with the Group1 frame images in c:\temp), so the only difference between Manual working (using frame images in Group1.mp4) and not working (using frame images in c:\temp) was where the frame images were coming from.
The Forum has topics on "Using Multiple Videos", which only discuss the merging of alignment and training faces - not the original frames file required to use the Manual option. I'm guessing that I can use the Update Hashes, which uses the names for matching, but there isn't much info on this.
I'm a bit lost in my understanding now - I hope I'm missing something obvious. Is there a way to merge frames so that a merged alignment file can access the landmarks properly?