问题
I used ffmpeg to generate a one-frame mjpeg video at the maximum possible quality, like this:
ffmpeg -i reference.png -frames:v 1 -codec:v mjpeg -q:v 1 -an 1.mkv
I also made a reference conversion to jpeg using imagemagick, at 85% quality:
convert reference.png -quality 85 85.jpg
The resulting "1.mkv" is only 83K, despite the fact that 85.jpg is 88K - and that's not even the highest possible jpeg quality.
At 95% imagemagick produces a file of 120K, and 207K at 100%. (Though it should be noted that image quality does not improve above 95%.) Since ffmpeg is set to maximum quality, I would expect frames of around this size.
Why are ffmpeg's mjpeg frames so small?
来源：https://stackoverflow.com/questions/50651998/why-is-the-maximum-ffmpeg-mjpeg-quality-so-low