ffplay - Two videos (.mp4), one display screen and just a few seconds to display them together [closed]

Question

I have two videos (.mp4), one display screen and just a few seconds to display them together.

I am able to displayed them together on a split screen via ffmpeg and then opening the output file. The problem is that it takes a long time (3 minutes).

Here is the Code: (first code)

ffmpeg -i _20180114094126_flightvideo_cam1.mp4      \
       -i _20180114094126_flightvideo_cam2.mp4       \
       -filter_complex "                              \
               [0:v]crop=1280:360:0:0[v0];             \
               [1:v]scale=1280:-1,crop=1280:360:0:0[v1];\
               [v0] [v1]vstack[v]" \
       -map [v]                     \
       -vcodec libx264               \
       -pix_fmt yuv420p               \
       -preset ultrafast               \
        6000screen_take1.mkv  

On the other hand, when using ffplay I am able to modify one video at the time and play it right away:

$ ffplay -i _20180114094126_flightvideo_cam1.mp4 -vf scale=425:-2 

How can I have the same outcome as the first code above, but display it on my screen right away(without waiting for the output file to be created, 3 minutes in this case)?

Please let me know if this is not clear.

Answer 1

Use

ffplay -f lavfi -i 
         "movie=20180114094126_flightvideo_cam1.mp4,crop=1280:360:0:0[v0];
          movie=_20180114094126_flightvideo_cam2.mp4,scale=1280:-1,crop=1280:360:0:0[v1];
         [v0][v1]vstack"