vf_fps outputs extraneous frame

[Illya]

Summary of the bug:
60fps.mp4 has 900 frames
out.avi has 451 frames, it should have 450

How to reproduce:

$ ~/Workspace/Multimedia/ffmpeg/ffmpeg/ffmpeg -i 60fps.mp4 -vf fps=30 out.avi
ffmpeg version N-81883-gbeb877b Copyright (c) 2000-2016 the FFmpeg developers
  built with Apple LLVM version 8.0.0 (clang-800.0.38)
  configuration: --samples=fate
  libavutil      55. 32.100 / 55. 32.100
  libavcodec     57. 60.101 / 57. 60.101
  libavformat    57. 51.102 / 57. 51.102
  libavdevice    57.  0.102 / 57.  0.102
  libavfilter     6. 63.100 /  6. 63.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  2.100 /  2.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '60fps.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41isomavc1
    creation_time   : 2016-10-03T21:26:33.000000Z
  Duration: 00:00:15.04, start: 0.000000, bitrate: 4115 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720 [SAR 1:1 DAR 16:9], 3861 kb/s, 60 fps, 60 tbr, 60 tbn, 120 tbc (default)
    Metadata:
      creation_time   : 2016-10-03T21:26:33.000000Z
      handler_name    : L-SMASH Video Handler
      encoder         : AVC Coding
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 256 kb/s (default)
    Metadata:
      creation_time   : 2016-10-03T21:26:33.000000Z
      handler_name    : L-SMASH Audio Handler
File 'out.avi' already exists. Overwrite ? [y/N] y
Output #0, avi, to 'out.avi':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41isomavc1
    ISFT            : Lavf57.51.102
    Stream #0:0(und): Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 30 fps, 30 tbn, 30 tbc (default)
    Metadata:
      creation_time   : 2016-10-03T21:26:33.000000Z
      handler_name    : L-SMASH Video Handler
      encoder         : Lavc57.60.101 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
    Stream #0:1(und): Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, stereo, fltp, 192 kb/s (default)
    Metadata:
      creation_time   : 2016-10-03T21:26:33.000000Z
      handler_name    : L-SMASH Audio Handler
      encoder         : Lavc57.60.101 ac3
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mpeg4 (native))
  Stream #0:1 -> #0:1 (aac (native) -> ac3 (native))
Press [q] to stop, [?] for help
frame=  451 fps=149 q=31.0 Lsize=    4749kB time=00:00:15.04 bitrate=2586.7kbits/s speed=4.98x
video:4365kB audio:352kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.669291%

Patches should be submitted to the ffmpeg-devel mailing list and not this bug tracker.

[Illya]

Since I cannot upload the samples (due to their size), I've uploaded them here:

​https://itanimul.li/tickets/5876/out.avi
​https://itanimul.li/tickets/5876/60fps.mp4

[Carl Eugen Hoyos]

I believe this is a duplicate of ticket #2674.