[FFmpeg-user] Intermediate video format for Concatenation of video and images

[Dzung Nguyen]

Hi all,

I'm converting image to videos, and then merging them together (because the
length of the image slideshow is random, not fixed).

1) Image --> video:

ffmpeg -loop 1 -f image2 -i image.png -c:v libx264 -tune stillimage -t 30
video1.mp4

2) Concatenate subvideos:

ffmpeg -f concat -i list.txt -c copy concatenated.mp4

Which format should I use when creating subvideos? I found that mpeg lose
the image quality, while using mp4 the output is unskippable.