[FFmpeg-user] Is a video generated with transitions different from a normal video?

[iburman at compuscience.com]

Looks like I figured it out. Removing the -c copy seems to solve the
problem.

Thanks to all that replied. 

-----Original Message-----
From: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> On Behalf Of
iburman at compuscience.com
Sent: Sunday, June 20, 2021 8:19 PM
To: 'FFmpeg user questions' <ffmpeg-user at ffmpeg.org>
Subject: Re: [FFmpeg-user] Is a video generated with transitions different
from a normal video?

Hi Rob,

I believe that your suspicion is correct, it has to do something with the
seek and the frames available. I tried to do several cuts just changing the
start and offset, and the results seem to confirm what you said:

Start = 0, duration 12 - works as expected; final video duration is 12 and
the transition starts where expected, at 7.
Start = 3, duration  9 - total duration 12, transition starts at 9 (so I
lost part of the transition which is 4 seconds) Start =5, duration= 7 -
totally crazy - final duration is 3 and didn't get to include the transition
part.

You asked: " Did you try without doing a combined stream copy and seek
apropos of my other reply?"

No, I didn't, as I don't know how to do that.

I see two options here:

1 - is there a different command that will allow ffmpeg to cut with more
precision respecting the stat and duration parameters? Perhaps this is what
you are suggesting, but I don't know how to do that.

2 - Perhaps there is a different command to generate the transition, so it
creates more frames during the transition, and consequently allows to cut
the final video with more precision. As I mentioned in my initial post, I
generate the transition with:

Ffmpeg -i v1.mp4 -i v2.mp4 -filter_complex
"xfade=transition=hlslice:duration=4:offset=7"  -pix_fmt yuv420p output.mp4

Is there a better way to do that?

Thanks

-----Original Message-----
From: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> On Behalf Of Rob Hallam
Sent: Sunday, June 20, 2021 7:42 PM
To: FFmpeg user questions <ffmpeg-user at ffmpeg.org>
Subject: Re: [FFmpeg-user] Is a video generated with transitions different
from a normal video?

On Sun, 20 Jun 2021, 15:51 , <iburman at compuscience.com> wrote:

> Ffmpeg -ss 6 -i input.mp4 -to 6 -c copy output.mp4
>

Did you try without doing a combined stream copy and seek apropos of my
other reply?

Rob

>
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