Clarification on cutting points, please.

Begonnen von Niky the Seal, Januar 06, 2020, 00:47:26

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Niky the Seal

I know this must seem like a very basic question to the experts here, but despite many attempts, I have been unable to avoid the ugly 'mosaic' artefacts that mar the video as it transitions at the cutting points during playback.
I've read through the entire forum history; only one discussion came close (Topic: "I-Frame Artefact", August 10, 2014) but still didn't answer the question definitively.

According to my understanding of GOP and Key Frames, I always manually select I-frames for my cutting points (and never use automatic advertisement recognition). I-frames usually don't correspond to where I ideally want to cut, but I can live with that!

I had some better success on HDTV recordings once I followed the suggestion to check the box 'I-frame only cutting' in Settings (although it seems odd that this would make a difference, as I was cutting on I-frames anyway!), but this setting has had no effect on SDTV (MPEG2) recordings where the artefacts remain.

I found a clue to this in the English-version manual, which says
ZitatAbout 3 frames before the next I-frame is the optimal CutOut points and about 2 frames before the next I-frame is the best place for the CutIn point
, however, (i) this contradicts the rule about cutting on key frames; (ii) 'about 3' or 'about 2' seems very inexact for something I presumed requires absolute precision; and (iii) it is in effect saying, "TS Doctor cuts at the GOP borders, but you should select cutting points outside of those borders".

In short, my requirement is very basic: SEAMLESS transitions between edits. Is this achievable without the need to resort to smart rendering??

Thanking you in advance for any advice, Niky.


Simple answer, NO.

Things are complicated, as in the meantime we not only have MPEG2 and H.264 but also H.265 (HEVC). And the more advanced the codecs get, the more complicated it all gets. There are thousands of parameters you can set for H.264 and H.265 and if one is different, you will get artefacts on the cutting points, even with smart encoding.

Niky the Seal

Thank you for the ultra-quick reply and sorry for bothering you with the long-winded question... it's something I've been grappling with for a while!

I understand your reply as suggesting that the problem is with the complex nature of the 'more advanced codecs' and you mention H264 and H265 specifically. However it's the original and far more common Standard Definition MPEG2 recordings that are still beset with ugly cutting artefacts after I process them with TS-Doctor. The results with H264 are significantly better now, definitely acceptable, with the abovementioned change in the settings. If it can be done for H264 then why not MPEG2?

Is it a hopeless case? I had hoped that perhaps using a different method of selecting cutting-points manually, or tweaking with the settings in some way, could make a difference?

If not, then to keep disturbances to a minimum for MPEG2 recordings, should I continue to select I-frames as cutting points, or better to follow the advice in the manual, "About 3 frames/about 2 frames before the next I-frame" ?


We are planing to have frame accurate cutting for MPEG2 with smart encoding but I can not tell how long it will take.

In the meantime it's recommended to cut 2 frames in front of an iframe as this will reduce the artefacts to 2 or 3 video frames as most encoders will create with  2 (depending) bframe in front of an iframe.


I donot see these artefacts when playing with vlc. mpc or Kodi.
I do see them with conversion (
Maybe try a different mediaplayer?


A clever player should only displays frame where all depending data is available.