[FFmpeg-trac] #7143(ffmpeg:new): Not stable fps in delivery rtmp stream

[FFmpeg]

#7143: Not stable fps in delivery rtmp stream
-------------------------------------+-------------------------------------
             Reporter:               |                     Type:  task
  pavel.khilko                       |                 Priority:  important
               Status:  new          |                  Version:  3.4
            Component:  ffmpeg       |               Blocked By:
             Keywords:  fps          |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:

 When flipping a thread with a given fps using the -vf "fps = 30" filter at
 the output when delivered, the value of fps fluctuates from 20 to 50-60
 peaks.
 The delivery of frames is controlled by ffprobe, which displays video
 frames and the code on JS counts the number of frames that came in a
 second.

 This behavior is observed only with non-stable input stream, provided
 uniform and stable flow of this problem at the output ffmpeg is not
 observed.
 Also, if we analyze Freeman by comparing the pkt_pts_time of received
 frames, the value of fps remains stable and equal to 30, as specified in
 the command.

 For video analysis, use the module "video-quality-tools"

 How to reproduce:
 - Emulate the incoming stream with delays in delivery
 - Accept ffmpeg input at this prompt
 - Output stream also will not have stable fps


 {{{
 % ffmpeg -i rtmp://localhost/myapp/myStream -s 1280x720 -aspect 16:9 \
 -c:a aac -b:a 64k -ac 2 -ar 44100 -c:v libx264 -b:v 1500k -minrate 1500k \
 -maxrate 1500k -bufsize 700k -profile:v main -level 4.0 -vf
 "fps=30,format=yuv420p" \
 -x264opts "keyint=60:min-keyint=60:no-scenecut" -preset veryfast \
 -tune zerolatency -threads 0 -f flv rtmp://localhost/myapp/myStream1


 ffmpeg version 3.4.2 Copyright (c) 2000-2018 the FFmpeg developers
   built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.9) 20160609
 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7143>
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