[Fix] Encoding result video with the same time scale as original

[X-Stuff]

Problem

Encoded videos with osd has different time scale values, this results problem when you trying to concatenate 2 mp4 video without re-enconding with ffmpeg. See refence on stackoverflow

Before

ffprobe -hide_banner AvatarG0000.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'AvatarG0000.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    creation_time   : 2000-03-16T04:00:29.000000Z
    encoder         : Lavf58.76.100
  Duration: 00:01:03.27, start: 0.000000, bitrate: 30815 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, smpte170m, progressive), 1280x720, 30813 kb/s, 60 fps, 60 tbr, 90k tbn (default)
      Metadata:
        creation_time   : 2000-03-16T04:00:29.000000Z
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]

ffprobe -hide_banner AvatarG0000_with_osd.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'AvatarG0000_with_osd.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf61.2.100
  Duration: 00:01:03.27, start: 0.000000, bitrate: 41639 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1280x720, 41633 kb/s, 60 fps, 60 tbr, 15360 tbn (default)
      Metadata:
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
        encoder         : Lavc61.4.100 libx264

Original tbn: 90k
With OSD tbn: 15360

After

>ffprobe -hide_banner AvatarG0000_with_osd.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'AvatarG0000_with_osd.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf61.2.100
  Duration: 00:01:03.27, start: 0.000000, bitrate: 41639 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1280x720, 41633 kb/s, 60 fps, 60 tbr, 90k tbn (default)
      Metadata:
        handler_name    : VideoHandler
        vendor_id       : [0][0][0][0]
        encoder         : Lavc61.4.100 libx264

With OSD tbn: 90k

Reviewer

@avsaase

[avsaase]

Hi @X-Stuff, sorry for taking to long for getting to this PR. I just merged another PR which created a conflict with this one. Can you rebase?