ffmpeg from pngs... Error with subset of PNGS? - ffmpeg

Question

I have about 1200 pngs that I'm converting into a movie. Some of them are missing: i.e. - _00003.png, _00005.png exist, but 1, 2, and 4 do not.
The following command works for other datasets, but not my current set of pngs:
ffmpeg -i pngs/_*.png -y -vcodec mpeg4 -pix_fmt yuv420p -r 25 -filter:v 'setpts=1.2*PTS' p3SN.mp4
I get this error:
Output #61, image2, to 'pngs/_00096.png':
Metadata:
encoder : Lavf57.83.100
Stream #61:0: Video: png, rgba, 3240x2160 [SAR 3937:3937 DAR 3:2], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
Metadata:
encoder : Lavc57.107.100 png
Output #62, image2, to 'pngs/_00097.png':
Metadata:
encoder : Lavf57.83.100
Stream #62:0: Video: png, rgba, 3240x2160 [SAR 3937:3937 DAR 3:2], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
Metadata:
encoder : Lavc57.107.100 png
[png # 0x7fae93170e00] ff_frame_thread_encoder_init failed
Error initializing output stream 63:0 -- Error while opening encoder for output stream #63:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!
at image _00097.png. If I remove it, it just happens a little later (105).
I've checked the images by looking at their dimensions, etc. and all of them in this range look the same (I checked all those with _0009?.png).
Any idea why this is happening?
Here's the offending file (middle) and the one before/after:

Answer 1

Your command will overwrite all of the input files with the first input. This is an example of why to use caution when using -y which will automatically overwrite files without asking you.
You need to tell ffmpeg to use the glob pattern:
ffmpeg -y -pattern_type glob -framerate 25/1.2 -i "pngs/_*.png" -vcodec mpeg4 -pix_fmt yuv420p -r 25 p3SN.mp4
I believe the glob pattern option does not work on Windows, but if it has an equivalent to the Linux cat command you can pipe the output: cat *.png | ffmpeg -i - output.mp4
You can use -framerate and -r instead of setpts if desired.