[FFmpeg-user] ffmpeg transitions not working

[Paul B Mahol]

On Sat, Jun 19, 2021 at 3:58 PM <iburman at compuscience.com> wrote:

> Yes, adding this parameter worked. Thanks for your suggestion, it allows me
> to generate the transitions I need...
> But I'm curious to understand why this parameter is required. All samples I
> was able to find for transitions, nobody included it.
> Also, both videos that I'm using are cut out from a larger video file, so
> all their encoding parameters are the same. Shouldn't ffmpeg have all the
> parameters it needs?
>
> As for the player, I am not using anything in special, it is the default
> that plays an mp4 in Windows 10. In task manager it shows up as Movies & TV
> with a process name of Video.Ui.exe and a child process of
> RuntimeBroker.exe. It works fine with all my mp4. Also, all videos
> generated
> with ffmpeg, like extracting a video, concatenate videos, etc., show fine
> with this player. Just the transition doesn't work.
>
> By the way, I tried to open the bad files with Media Player and it also
> shows all black. It doesn't seem to be a player issue.
>
> An additional question - although your suggestion worked, the generation of
> the file also took a long time, like with my unsuccessful trials. Are
> transitions expected to take so long time? I'm wondering because everything
> else I did with ffmpeg so far has been very fast.
>
> Please excuse my questions, the video manipulation is quite new for me...:)
>

Filtering, unlike remuxing, can be slow as it needs to decode and encode
output.
To make it faster you need to use cuts in such a way so no excessive
decoding ( so offset is always 0) is ever done.


>
> Thanks for your help
>
>
>
> -----Original Message-----
> From: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> On Behalf Of Gyan Doshi
> Sent: Saturday, June 19, 2021 3:56 PM
> To: ffmpeg-user at ffmpeg.org
> Subject: Re: [FFmpeg-user] ffmpeg transitions not working
>
>
>
> On 2021-06-19 18:22, iburman at compuscience.com wrote:
> > I'm having problems with transitions. To be sure I am not making
> > something wrong, I simply copy/paste the example shown in
> > https://ffmpeg.org/ffmpeg-filters.html#xfade, adjusted my two video
> > file names to comply with the example, and got the same problems as
> > with my own commands.
> >
> >
> >
> > The example on the site shows this: ffmpeg -i first.mp4 -i second.mp4
> > -filter_complex xfade=transition=fade:duration=2:offset=5 output.mp4
> >
> > My first and second files have 1 min each.
> >
> >
> >
> > First I run the command without any change; obviously offset 5 isn't
> > appropriate but I gave it a try.
> >
> > Second I adjusted duration to 10 and offset to 55 to be appropriate
> > with my two mp4 files. The result was the same:
> >
> > The final output.mp4 has the right duration (1:55) but it is totally
> black.
> >
> >
> >
> > What I see during execution is that the first video is read/copied to
> > output.mp4 quite fast. After that it starts reading second.mp4 and
> > works a very long time on it, probably close to one minute.
>
> Which player?
>
> Try
>
>      ffmpeg -i first.mp4 -i second.mp4 -filter_complex
> xfade=transition=fade:duration=2:offset=5 -pix_fmt yuv420p output.mp4
>
>
> Regards,
> Gyan
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