[FFmpeg-user] I found the bugs

[Paul B Mahol]

On Tue, Jun 18, 2024 at 12:00 AM Mark Filipak <markfilipak.imdb at gmail.com>
wrote:

> On 17/06/2024 17.18, Paul B Mahol wrote:
> > On Mon, Jun 17, 2024 at 8:29 PM Mark Filipak <markfilipak.imdb at gmail.com
> >
> > wrote:
> >
> >> On 17/06/2024 13.50, Paul B Mahol wrote:
> >>> On Mon, Jun 17, 2024 at 5:35 PM Mark Filipak <
> markfilipak.imdb at gmail.com
> >>>
> >>> wrote:
> >>>
> >>>> On 17/06/2024 03.16, Paul B Mahol wrote:
> >>>>> On Mon, Jun 17, 2024 at 3:16 AM Mark Filipak <
> >> markfilipak.imdb at gmail.com
> >>>>>
> >>>>> wrote:
> >>>>>
> >>>>>> To expand on my idea:
> >>>>>>
> >>>>>> The video is this:
> >>>>>> I P B B P B B P B B I P B B..
> >>>>>> I want to change it to this:
> >>>>>> I B B P B B P B B P I B B P..
> >>>>>>
> >>>>>
> >>>>> If this is what I think it is, your are wasting your time.
> >>>>
> >>>> It is possible. But can FFmpeg do it? You see, Paul, I read in several
> >>>> places from seemingly
> >>>> authoritative people that professional videos are PTS-ordered. I've
> >> since
> >>>> discovered that
> >>>> professional videos are almost always DTS-ordered -- I now have a
> packet
> >>>> browser and have seen it to
> >>>> be true. However, I have seen professional videos that are PTS-ordered
> >> but
> >>>> I didn't think too much
> >>>> about it at the time.
> >>>
> >>> PTS order is order once frames are decoded and going to be presented to
> >>> user, thats why it is called presentation timestamps.
> >>
> >> Yes of course.
> >>
> >>>> My idea is to take the 4-second video -- DTS-ordered -- that I sent to
> >>>> trac, change it to
> >>>> PTS-ordered, and see if '-vf showinfo' and '-f show_frames' respond
> >>>> correctly. It's a long shot, but
> >>>> it might show something useful -- what if PTS-order made showinfo
> >>>> show_frames and framecrc all
> >>>> agree? Wouldn't that be something interesting?
> >>>
> >>> If decoder follows specifications for decoding bitstreams correctly
> than
> >>> changing order of raw encoded frames as stored in bitstream will almost
> >>> every-time cause broken decoding.
> >>>
> >>>>> Its nonsense to change order of encoded frames, no manipulation of
> >> clock
> >>>>> can fix that.
> >>>>
> >>>> No, no. Manipulation of PCR. Fix up the PCRs so that the result is
> truly
> >>>> PTS-ordered.
> >>>
> >>> If this is at format container layer, I dunno how would that work even
> if
> >>> its is possible to be useful.
> >>
> >> The container would contain a PES packet stream with PCRs like any other
> >> PES packet stream. It would
> >> work like any PTS-ordered stream does. You know, there _are_ PTS-ordered
> >> streams. And you know, MPEG
> >> is silent on the matter of what physical order frames are in the stream,
> >> only that they must be
> >> given to the decoder in DTS-order.
> >>
> >> Look, I agree that it would be nonsense. I want to turn the DTS-ordered
> >> stream into a PTS-ordered
> >> stream merely as a test: '-f show_frames' appears to be getting DTSes
> and
> >> PTSes mixed up, then
> >> applying a fix that results in completely new DTSes. If it treats the
> >> PTS-ordered stream
> >> differently, that will say a lot. What is says depends on what it does.
> >> Capiche?
> >>
> >> I thought I could do it by demuxing, then moving them like you can move
> >> frames in a filter_complex,
> >> and then remuxing, but I don't know how to do that to PES packets
> (instead
> >> of decoded pictures) and
> >> I don't know how to rewrite PCRs.
> >>
> >
> > But aren't you working with HEVC and not MPEG video?
>
> I'm working with AVC-M2TS, then transcoding-remuxing to HEVC-MP4.
>
>
So you operate with bsf filters to create HEVC output?


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