Solar eclipse converting AVCHD to image sequences...

[jeff d]

I've got lots of video files of the eclipse and want to use some tools which can align the video frame to correct for the earth's movement. I've seen a java program made for medical imaging called ImageJ that has some plugins which may be helpful and I want to give those a try.

I'd like to use Vdub to create the images but I've run into a problem I don't know how to correct. The source files are Canon AVCHD files recorded at 1440x1080 and when vdub outputs the image sequence it does as 1440x1080 (surprise!). But this display aspect ratio isn't correct as this is a HD (16:9) format. I can't find how to adjust the DAR for the source files. Is there a way to get vdub to output an image sequence with a correction for the 16:9 DAR?

My recordings were several 4 minute clips where the sun/moon move from the upper left to lower mid edge and I'm hoping to post process this to center everything. I'm also interested in hearing other ideas there are better ways.

I've attached an image to show what I mean about the AR on the images...

[poisondeathray]

You would use a vdub resize filter to 1920x1080 before exporting

Very cool image! We didn't get as good of an angle in Canada

[KarMa]

AVCHD supports full 1920x1080 and 1440x1080 (usually used to reduce bitrate), but obviously you used 1440x1080 mode. So in vdub you can use a resize filter like lanczos3 to get 1920x1080. Another thing is that your image has slight hits of interlacing, so if you recorded at 29.97fps or 25fps then it is interlaced. Some AVCHD cameras (maybe all) support 23.976 progressive recordings with AVCHD which would not require deinterlacing.


[Attachment 42915 - Click to enlarge]

[jeff d]

Yes KarMa you are correct. Thanks. This AVCHD was recorded in the 1440x1080 mode, it was also interlaced with 29.97 fps. I should have done 60p, but didn't even think about it. I've found the sports stuff I normally shoot at 60p wasn't as smooth (not logical) as the 60i recordings. So I've been interlaced since making that discovery. 24p would have likely been my best choice given this subject... but I didn't think it through, even with all the advance notice I didn't think of it. Worse yet, I should have remembered my Canon Rebel can only shoot like 5 minutes of video before stopping, I lost my other view, the lake and mountains being covered in darkness. I'll try to do better in 2024!!

VLC reports back it's recorded 1440x1090 with a display resolution of 1440x1080. Obviously that makes this more anamorphic which is why I was looking at using vdub to do the image sequences so I can "line up" things. What I've seen is that vdub doesn't do any processing on the image sequence output. I could be wrong, but I tried to resize (simple bicubic test) and results look the same. I'll try again, but maybe there's a better way to do this. I was considering preprocessing with avisynth, and that may be the correct thing to do. This will also allow for some adjustments to contrast, brightness and color.

AVISynth/Vdub image sequence may be the best option unless someone has done something similar with good results.

[jeff d]

After a bit more research it seems this could be a square vs non-square pixel thing. Does that make sense, and is there anything which will display the image with an non-square pixel AR?

@poisondeathray, thank. from what I've seen if your near Montreal you'll have a good view in 7 years.

[jagabo]

After a bit more research it seems this could be a square vs non-square pixel thing.

That's exactly what it is.

and is there anything which will display the image with an non-square pixel AR?

You were told what to do in earlier: resize to 1920x1080 or some other 16:9 frame size (players do this automatically at playback) . Be sure to disable the "Aspect ratio" option in VirtualDub's resize filter so it doesn't try to retain the 4:3 frame aspect ratio of your source. And if you change the vertical size you must deinterlace first.

[jeff d]

Thanks, I've been using the filter sequence of de-interlace (went with default setting since it's the sun and slow enough there's very little interlacing that I can see), resize (Lanczos3). I had hoped there would be a way to not resize but also figured it couldn't be avoided.

The next challenge will be to align the sun in all the sequences as it moves slowly across the image area. This may prove to be my biggest problem because it's a small area and does move across a large area of the image. The result may end up having to be cropped and repositioned on a larger "black" background I have when the video was shot through a solar lens. From the earlier shot you can tell the sun use up to 1/4 of the image area and moves in my 2-4minute clips. This may be more difficult than I expected. I've tried photoshop's image import with alignment (that' really slow, maybe wasn't good to test with a 4000 image sequence?!?!). I may start searching vdub/avisynth plugins to help if anyone else has done something like this before. Sadly I can't even think of another situation where someone would need to do this...

[poisondeathray]

You don't have to resize; you can encode it with a 16:9 flag like your source. But only media players will play it back properly. If you upload it to a website like youtube it will be "squished" . So it's "better" to resize to "square pixel" equivalents - because it will playback properly everywhere

The general term used for aligning the images in video is "stabilization" . But it can be challenging for these types of shots because the objects are often featureless or smooth, or change shape (e.g. if you have a lens flare in some angles). There are different types of motion tracking and stabilization software, but they will probably all have some problems with this type of shot and require some manual intervention on some sections (it won't be completely automatic)