[FFmpeg-trac] #6975(undetermined:new): Recent change to sync video output to screen refresh conflicts with -noframedrop

FFmpeg trac at avcodec.org
Mon Jan 22 11:03:02 EET 2018

#6975: Recent change to sync video output to screen refresh conflicts with
             Reporter:  Misaki       |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0

Comment (by Misaki):

 What probably happened is that ffplay now pays attention to the
 {{{vblank_mode}}} environment variable.  From

  time (  time ffplay -autoexit -noframedrop black.mp4 )
  time (  ffplay -autoexit -noframedrop black.mp4 )

 real: 20 seconds

 {{{ time (  vblank_mode=0 ffplay -autoexit -noframedrop black.mp4 )}}}

 real: 13.4 seconds

 I thought that {{{vblank_mode=0 time ffplay [...]}}} reduced it to 10
 seconds, but what was actually happening was that I have an alias of
 ffplay to 'ffplay -hide_banner -noframedrop', and for some reason the
 temporary environment variable and 'time' makes it so the alias isn't

 I think it's enough though, and ffplay just doesn't speed late frames up
 to 2x speed, only to 1.5x speed.

 I assume this environment variable has been set this way for a long time,
 since I was familiar with glxgears syncing to vertical refresh.

 This may still be a bug, if users don't expect to have to deal with this
 non-ffmpeg setting in order to get 60 fps videos to work with

Ticket URL: <https://trac.ffmpeg.org/ticket/6975#comment:1>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker

More information about the FFmpeg-trac mailing list