[FFmpeg-user] JPGs->video1 ; MOV -> Mp4 video2 ; Concatenate - video2 audio OK but video is slow . .

[Philip Rhoades]

People,

I converted 21 JPGs to a video with:

   ffmpeg -f concat -i concat_demuxer1.txt -vf scale=1024:576 -r 29.97 
output1.mp4

I then added a silent audio track with:

   ffmpeg -ar 44100 -acodec pcm_s16le -f s16le -ac 2 -channel_layout 2.1 
-i /dev/zero \
     -i output${i}.mp4 \
     -vcodec copy \
     -acodec aac \
     -shortest output${i}_silent.mp4

I had another MOV file (fr=29.97) that I converted with:

   newfn=`basename $fn .MOV`
   ffmpeg  -i $fn -vf scale=1024:576 ./${newfn}.mp4

When I concatenate them with (and other converted JPGs and MOVS on the 
end) using:

   ffmpeg -f concat -i inputs.txt -vcodec copy -acodec copy \ 
2019-03-22_#1_XR_ClimateEmergencyDeclarationDayNSW_LoRes.mp4

the concat succeeds OK but when I play the video, the audio is OK but 
then when it gets to the converted MOV section, people are moving in 
slow motion . .

Another odd thing, the first 21 converted JPGs at 4 sec each correctly 
shows 84 sec when viewed with mpv but when the converted MOV starts it 
jumps to ~3m 50s . .

So there is at least one problem but maybe two?  Can anyone tell me what 
I am missing?

Thanks,

Phil.
-- 
Philip Rhoades

PO Box 896
Cowra  NSW  2794
Australia
E-mail:  phil at pricom.com.au