On Mon, Feb 12, 2024 at 2:24 AM Mark Filipak <markfilipak.i...@gmail.com> wrote:
> On 11/02/2024 17.39, Paul B Mahol wrote: > > On Sun, Feb 11, 2024 at 11:08 PM Mark Filipak < > markfilipak.i...@gmail.com> > > wrote: > >> On 11/02/2024 16.42, Paul B Mahol wrote: > >>> Codec copy with -ss before -i and after -i is not documented that it > gives > >>> different results > >> > >> Does that make sense? I think it's not documented because no one knows > how > >> to explain the results. > > > > It is self explanatory. > > Hahaha... That's funny. You're a comedian, Paul. > > >>> because once you do not decode everything from start you basically can > >>> not expect to get always (for any container and for any input) > >>> frame-accurate results in both cases. > >> > >> I don't think decoding is being done. The cutting/trimming can be by > >> dropping packets & remuxing. > >> The packets have to be 'opened' to read the PTSs, but I don't think > >> there's actual decoding. > > > > Packets here are just demuxed, not decoded. So -c copy will demux, so > > sample accurate audio seeking is not possible. > > > >> '-ss'-before-'-i' is cutting at the right point. > > > > That one actually seeks without demuxing each packet from start. > > I think we're getting closer to my problem. So '-ss'-before-'-i' looks at > the packet headers and the > PES headers, but only individually. It doesn't form streams until it gets > to the cut point. Then it > begins forming the various streams. Is that what you mean? > > >> '-i'-before-'-ss' is cutting at the wrong point. > > > > This one does not seek at all, it just demux from start and drops packets > > up to certain point. > > So, wouldn't the end result be the same? Many people have said that but > that's not been my > experience. Not at all. > > > For -c copy, that one demuxes from start (without any seeking, but just > > skipping packets processing) but gives output only after timeline point. > > Sorry. "That one"? Which one? They both have '-c copy' of course. > > > Which is kind of logical because it does not decode at all. And for > complex > > codec that have different forward/backward frame predictions it will give > > incorrect results because PTS may not match DTS - presentation timestamp > vs > > demux timestamp. > > DTS is not demux timestamp. And what do you mean by "it"? What is the > antecedent of "it"? I'm lost > in your explanation. > > > So for '-c copy' -ss after -i is mostly not useful, exp. for complex > > video/audio codecs with complex interframe coding. > > As I wrote earlier in this thread, I did '-i'-before-'-ss' on a lark to > see if it would be better. > It was worse. > > So, it seems like I have the operations right and that they should be the > same but they're not. > Operations are different and logically gives different results almost always in any situation. > > Correct? Are you saying that '-ss'-before-'-i' & '-i'-before-'-ss' should > be identical? > I never said such nonsense, and it is not bug of any sort. I could be beneficial to explicitly mention that -c copy is not frame accurate (no matter what position of -ss). > > > _______________________________________________ > ffmpeg-user mailing list > ffmpeg-user@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe". > _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".