FFMpeg custom command (mp4 output) don't work with mocha (black white frames)

[VegethB]

the default command generates too low quality .jpg and gives problems if you do a 1 minute trim (since prefix doesn't work).

So I searched for a commando for ffmpeg and found 2:

"#{encbin}" -ss #{startt} -sn -an -i "#{inpath}\#{input}" -vframes #{lenf} -c:v libx264 -r 24000/1001 "#{prefix}/#{output}[#{startf}-#{endf}].mp4" from #45

"#{encbin}" -ss #{startt} -sn -an -i "#{inpath}/#{input}" -to #{endt} -copyts -map 0:v "#{prefix}/#{output}[#{startt}-#{endt}].mp4"

both do the trim ... Except that when opened on mocha the frames are all black or white.
If you open the file on mediainfo under duration (in general):
For the first command it is the duration of the source video file (ex, 1 hour instead of 2 seconds);
For the second command it is the duration in the -to parameter (ex, 44minutes and 21seconds instead of 2seconds);

First Command:

Second Command:

I don't understand how to fix

[VegethB]

Fix, add -pix_fmt yuv420p after -crf 4
it seems that quicktime needs forced "4: 2: 0" or from the above problems.

Final Command:
"#{encbin}" -ss #{startt} -sn -an -i "#{inpath}\#{input}" -vframes #{lenf} -c:v libx264 -r 24000/1001 -crf 4 -pix_fmt yuv420p "#{prefix}/#{output}[#{startf}-#{endf}].mp4"