[FFmpeg-user] How to make IDR cuts

[David Niklas]

Just a quick heads-up, you seem to have forgotten to put any text in your
message, Mr. Shupert. It just quotes mark's email.

You're welcome,
David

On Sat, 20 Apr 2024 17:26:20 -0400
jim shupert <shupert.jim at gmail.com> wrote:
> On Wed, Apr 3, 2024 at 8:02 AM Mark Filipak <markfilipak.imdb at gmail.com>
> wrote:
> 
> > Is there more to this? If there is, it's not evident to me.
> >
> > If there are several B-frames in a row, then adjust your mind to 'see'
> > larger shifts across the
> > multiple B-frames and adjust PTSs & DTSs to match.
> >
> >
> > Cutting off a leading open GOP:
> >                  <————open GOP————>  <—————closed GOP——————>
> > PTS order      [_I_][_B_][_P_][_B_][_I_][_B_][_P_][_B_][_P_][_I_]
> >                __/  ___¦___/  ___¦___/  ___¦___/  ___¦___/  __/
> >               /    /   ¦     /   ¦     /   ¦     /   ¦     /
> > DTS order [_I_][_P_][_B_][_I_][_B_][_P_][_B_][_P_][_B_][_I_]
> >              X    X    X         X
> >
> > PTS order                          [_I_][_B_][_P_][_B_][_P_][_I_]
> >                                    __/  ___¦___/  ___¦___/  __/
> >                                   /    /   ¦     /   ¦     /
> > DTS order                     [_I_][_P_][_B_][_P_][_B_][_I_]
> >
> > Cut on PTS, then fix up the 1st DTS & packet SCRs.
> >
> > Or, I don't think it's going to hurt anything to leave this:
> > PTS order                          [_I_][_B_][_P_][_B_][_P_][_I_]
> >                               _______/  ___¦___/  ___¦___/  __/
> >                              /         /   ¦     /   ¦     /
> > DTS order                [_I_]     [_P_][_B_][_P_][_B_][_I_]
> > and just fix-up the packet SCRs.
> >
> > =====
> > Cutting off a leading closed GOP:
> >                  <—————closed GOP——————>  <————open GOP————>
> > PTS order      [_I_][_B_][_P_][_B_][_P_][_I_][_B_][_P_][_B_][_I_]
> >                __/  ___¦___/  ___¦___/  __/  ___¦___/  ___¦___/
> >               /    /   ¦     /   ¦     /    /   ¦     /   ¦
> > DTS order [_I_][_P_][_B_][_P_][_B_][_I_][_P_][_B_][_I_][_B_]
> >              X    X    X    X    X
> >
> > PTS order                               [_I_][_B_][_P_][_B_][_I_]
> >                                         __/  ___¦___/  ___¦___/
> >                                        /    /   ¦     /   ¦
> > DTS order                          [_I_][_P_][_B_][_I_][_B_]
> >
> > Just cut it and fix-up the packet SCRs.
> >
> > =====
> > Cutting off a trailing GOP from a closed GOP:
> >                  <—————closed GOP——————>
> > PTS order      [_I_][_B_][_P_][_B_][_P_][_I_]..
> >                __/  ___¦___/  ___¦___/
> >               /    /   ¦     /   ¦
> > DTS order [_I_][_P_][_B_][_P_][_B_]
> >
> > Just cut at the end of the closed GOP.
> >
> > =====
> > Cutting off a trailing GOP from an open GOP:
> >                  <————open GOP————>
> > PTS order      [_I_][_B_][_P_][_B_][_I_]..
> >                __/  ___¦___/  ___¦___/
> >               /    /   ¦     /   ¦
> > DTS order [_I_][_P_][_B_][_I_][_B_]
> >
> > PTS order      [_I_][_B_][_P_][_B_][_I_]
> >                __/  ___¦___/  ___¦___/
> >               /    /   ¦     /   ¦
> > DTS order [_I_][_P_][_B_][_I_][_B_]
> >
> > Cut retaining an ending I-frame, only.
> >
> >
> > Honestly, I don't know why the MPEG folks don't supply illustrations
> > instead of their torturous text.
> >
> > This isn't magic, it's Legos.
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> >
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> >  
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