[FFmpeg-user] Cutting on video frame

[Louis Letourneau]

On Jul 7, 2016 13:08, "Christian Ebert" <blacktrash at gmx.net> wrote:
>
> * Louis Letourneau on Thursday, July 07, 2016 at 12:38:26 -0400
> > When cutting a video, even when transcoding, I often have a small delay
> > between the video and audio.
> >
> > When looking at the video with either vlc or ffplay, I see the first
frame
> > shown twice.(The first is probably a dup until it the real pts is hit).
> >
> > I was wondering if there is a way to force cutting on video frame
> > boundaries to avoid this.
> >
> > Also when using -ss to cut exactly to the video frame closest to where I
> > want to cut. I still often get audio packets and frames with negative
pts.
>
> You may be interested in this:
> https://trac.ffmpeg.org/ticket/3859
>
> Basically there's always some aac padding. I usually resort to
> the atrim filter to butcher that off at the beginning, and
> sometimes other nasty stuff.
>
> > If It then convert this video from mp4 -> hls, the negative frames are
now
> > positive and my video frame is push forward again.
>
> Yeah, the behavior of the hls or other segment muxers doesn't
> make things easier.

This is great I didn't find that issue and I did look. It's exactly my
problem.

I'll fiddle with atrim and see where it leads me.

Thank you very much
Louis