Bad input frame rate estimation

[qianliang]

Summary of the bug:
How to reproduce:

% ffmpeg -i input.ts -c copy output.mp4
Input #0, mpegts, from 'input.ts':
  Duration: 00:00:59.43, start: 62.100000, bitrate: 1623 kb/s
  Program 1
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
    Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 640x480, 20 fps, 40 tbr, 90k tbn, 40 tbc
Output #0, mp4, to 'output.mp4':
  Metadata:
    encoder         : Lavf56.9.100
    Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 640x480, q=2-31, 20 fps, 90k tbn, 90k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
frame= 1488 fps=0.0 q=-1.0 Lsize=   10781kB time=00:00:59.40 bitrate=1486.9kbits/s
video:10767kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.128117%
ffmpeg version
ffmpeg version N-66797-gb8a5599
built on http://ffmpeg.zeranoe.com/builds/

It shows output.mp4 with 20 fps. But

% ffmpeg -i output.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'output.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.9.100
  Duration: 00:00:59.45, start: 0.000000, bitrate: 1485 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480, 1483 kb/s, 25.03 fps, 40 tbr, 90k tbn, 4
0 tbc (default)
    Metadata:
      handler_name    : VideoHandler

The fps changed to 25.03 fps

[qianliang]

But copy to mkv and flv, it came out the same fps value(20) as ts.
Here is my source video:
​https://www.dropbox.com/s/8hi6zwggo129xt4/input.ts?dl=0

[Carl Eugen Hoyos]

How did you create the input file?

[qianliang]

First I do segment operation:

ffmpeg -i source.ts -map 0:v -f segment -segment_time 60 source_video_%d.ts

And do convert oeration:

ffmpeg -i source_video_0.ts -vcodec libx264 -vb 1200k -maxrate 1800k -bufsize 3600k -r 20 -vprofile main -pix_fmt yuv420p -flags +loop+mv4 -cmp 256 -partitions +parti4x4+partp8x8+partb8x8 -me_method hex -subq 7 -coder 1 -trellis 1 -refs 4 -me_range 16 -sc_threshold 40 -i_qfactor 0.71 -qcomp 0.6 -qmin 15 -qmax 45 -qdiff 4 -rc_eq 'blurCplx^(1-qComp)' -tune zerolatency -x264opts keyint=120:min-keyint=25:b-pyramid=0:weightp=0:interlaced=0:mixed-refs=1:8x8dct=1 -vsync 0 -copyts input.ts

Here comes out the input.ts

[qianliang]

I find that adding filter "fps=20" while do convert operation, which would fix this problem:

ffmpeg -i source_video_0.ts -filter_complex "fps=20" -vcodec libx264 -vb 1200k -maxrate 1800k -bufsize 3600k -r 20 -vprofile main -pix_fmt yuv420p -flags +loop+mv4 -cmp 256 -partitions +parti4x4+partp8x8+partb8x8 -me_method hex -subq 7 -coder 1 -trellis 1 -refs 4 -me_range 16 -sc_threshold 40 -i_qfactor 0.71 -qcomp 0.6 -qmin 15 -qmax 45 -qdiff 4 -rc_eq 'blurCplx^(1-qComp)' -tune zerolatency -x264opts keyint=120:min-keyint=25:b-pyramid=0:weightp=0:interlaced=0:mixed-refs=1:8x8dct=1 -vsync 0 -copyts input.ts

[Carl Eugen Hoyos]

Replying to qianliang:

ffmpeg -i source_video_0.ts -vcodec libx264 -vb 1200k -maxrate 1800k -bufsize 3600k -r 20 -vprofile main -pix_fmt yuv420p -flags +loop+mv4 -cmp 256 -partitions +parti4x4+partp8x8+partb8x8 -me_method hex -subq 7 -coder 1 -trellis 1 -refs 4 -me_range 16 -sc_threshold 40 -i_qfactor 0.71 -qcomp 0.6 -qmin 15 -qmax 45 -qdiff 4 -rc_eq 'blurCplx^(1-qComp)' -tune zerolatency -x264opts keyint=120:min-keyint=25:b-pyramid=0:weightp=0:interlaced=0:mixed-refs=1:8x8dct=1 -vsync 0 -copyts input.ts

Using -r 20 and -vsync 0 together leads to invalid files, in your case a file with 25fps (25 actual frames per second) that looks like a 20fps file.
You are requesting put 20 files per second in the output stream and keep 25 frames per second, don't drop or duplicate any frames. It is impossible for ffmpeg to fulfill both requests, I just sent a patch that prints a message if both options were specified.

[Carl Eugen Hoyos]

A patch was pushed that prints an error message if -vsync 0 and -r are used together.