[FFmpeg-user] stepping one frame at a time in ffplay

[Dave Rice]

Hi all,
I'm trying to use ffplay to identify a particular frame number. First I start ffplay with
ffplay -vf showinfo MOVIE

I'm hoping to then navigate around the file to find the frame I'm interested in and then have another process parse the frame number from showinfo that I am currently on. When I try this I find there are very few fine controls in ffplay. If I want to back up 3 frames there doesn't seem to be a way to do it easily. I can click on the ffplay windows to jump around or click left which jumps back many seconds. In order to get the frame number I want it seems that I have to play up to the frame and hit pause at exactly the right time, else there is no way to step backwards a few frames to find the right one. Is there a way to change the amount of jump in the left and right controls? Is there a complete list of ffplay keyboard shortcuts. It would be great to incorporate more keyboard controls such as j/k/l as used in Final Cut and Quicktime and buttons to go forward or back by single frames.

Best Regards,
Dave Rice

[Carl Eugen Hoyos]

Dave Rice <dave <at> dericed.com> writes:

[...]

Something unrelated first:
Please remember that not everybody reading this mailing
list is a (English) native speaker and it is mostly read
by people in their free time so while too short mails
are of course very bad and you should typically explain
what you are trying to do I wonder if the following
would have been sufficient:
"
I want to seek forward and backward frame-wise with
ffplay, this works fine with FCP but I did not find
out how to do it with ffplay although I read the fine
documentation carefully.
"
(Sorry if I miss something, see above for a possible
explanation.)

You can use "s" to step forward one frame (documented
at the end of "ffplay -h").
Implementing stepping backwards is not trivial, this
is a very, very long-known feature request.

Carl Eugen

[Carl Eugen Hoyos]

Post by Dave Rice
Is there a way to change the amount of
jump in the left and right controls?

Sorry, I forgot:
This can be easily changed in ffplay.c
(search for "SDLK_PAGEUP" but I am not
sure how much this will help with your
original problem.
(You can change LEFT/RIGHT to "3" but
you will find streams where three seconds
is often not enough to seek backwards.)

Carl Eugen