[FFmpeg-user] How to decode one frame and encode one jpg if using qscale

[Carl Eugen Hoyos]

Am Di., 17. März 2020 um 16:04 Uhr schrieb penguin flying
<theflyingpenguin2020 at gmail.com>:
>
> using this cmd
> ffmpeg -i in.mp4  -copyts -f image2 -vframes 5   -y %03d.jpg
> will decode one frame and then encode it to one jpg at the same time,
> AND the picture will be encoded in default quality.
>
> BUT when I want to improve the quality of the image after adding the param
> "qscale",
> ffmpeg -i in.mp4  -copyts -f image2 -vframes 5 -qscale:v 2   -y %03d.jpg
>
> I found that three or more frames must be send to the encoder before the
> first jpg comes out.
>
> How to send one frame and then one picture out when using "qscale"

The output option -threads 1 should ensure this...

> PS: the source file  in.mp4 has B frames

... but this may not be possible for streams with B frames.

Carl Eugen