get-iplayer & youtube-dl issue from BBC TOTP (frames out of correct order)

[fbr$]

Hi, until last week (8 days ago) I was downloading every TOTP (Top of the Pops) new episode released on Friday nights using get-iplayer (for macOS) on the highest quality (720p50).

(I'm using the latest versions of all apps and of macOS, so don't need to ask me which versions I'm using)

But "18/10/1990" and "25/10/1990" (dd/mm/yyyy) episodes downloaded yesterday are defective.

I always open the mp4 file on QuickTime Player and check it frame by frame, pausing the video and going frame by frame with the right arrow key on the keyboard to check for issues.

Tried to download the same two episodes using youtube-dl too, I got mixed results:

1) downloading a single mp4 file with youtube-dl using the "--format best" option, it has the same issue as the get-iplayer mp4 file;

2) downloading two individual streams, video and audio (it's the default behaviour), it seems I got a perfect video stream.

Opening the defective video.mp4 file on MKVToolNix, exporting as video.mkv file, then on Terminal doing "mkvextract video.mkv timestamps_v2 0:timestamps.txt", I got a timestamps.txt like this:

# timestamp format v2
0
40
40
60
80
100
120
140
160
200
200
220
240
260
280
300
320
360
360
380

As you can see, there are wrong timestamps:

40 is repeated in two diferent frames (20 is missing),
same for 200 (180 is missing)
etc.

Fixed it creating a new timestamps.txt file:

# timestamp format v1
assume 50.000

Then used MKVToolNix to add the new timestamps.txt file to a new mkv file, then used mkvextract again to check it out, now I got:

# timestamp format v2
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
380

Now everything seems OK.

Then I converted the mkv file to mp4 using Subler for macOS.

Played the new mp4 file on QuickTime Player and played the new mkv file on VLC.

But the issue on playback is still there: the video has some jumps in the motion, it jumps a frame (creating a hole in the motion) and then in the next frame right after the jump it goes back to the jumped frame (where there was the hole).

Downloaded the same "18/10/1990" TOTP episode on the BBC website to play it on the BBC iPlayer Downloads app, it seems fine here, no issue, smooth playing.