Quoting Gyan Doshi (2022-07-10 20:02:38) > > > On 2022-07-10 10:46 pm, Anton Khirnov wrote: > > Quoting Gyan Doshi (2022-07-08 05:56:21) > >> > >> On 2022-07-07 03:11 pm, Anton Khirnov wrote: > >>> Quoting Gyan Doshi (2022-07-04 18:29:12) > >>>> This is a per-file input option that adjusts an input's timestamps > >>>> with reference to another input, so that emitted packet timestamps > >>>> account for the difference between the start times of the two inputs. > >>>> > >>>> Typical use case is to sync two or more live inputs such as from capture > >>>> devices. Both the target and reference input source timestamps should be > >>>> based on the same clock source. > >>>> > >>>> If not all inputs have timestamps, the wallclock times at the time of > >>>> reception of inputs shall be used. FFmpeg must have been compiled with > >>>> thread support for this last case. > >>> I'm wondering if simply using the other input's InputFile.ts_offset > >>> wouldn't achieve the same effect with much less complexity. > >> That's what I initially did. But since the code can also use two other > >> sources for start times (start_time_realtime, first_pkt_wallclock), > >> those intervals may not exactly match the difference between > >> fmctx->start_times so I use a generic calculation. > > In what cases is it better to use either of those two other sources? > > > > As per the commit message, the timestamps of both inputs are supposed to > > come from the same clock. Then it seems to me that offsetting each of > > those streams by different amounts would break synchronization rather > > than improve it. > > The first preference, when available, stores the epoch time closest to > time of capture. That would eliminate some jitter. > The 2nd preference is the fmctx->start_time. The 3rd is the reception > wallclock. It is a fallback. It will likely lead to the worst sync.
You did not answer my question. If both streams use the same clock, then how is offsetting them by different amounts improve sync? -- Anton Khirnov _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
