[SOLVED] FFmpeg to assemble a video, how to?

rdx · 05-12-2016, 06:30 AM

Quote:

Originally Posted by notKlaatu

I would not entrust chroma key to ffmpeg; for a good key, you really do need to interact with the filter. The 'right' thing to do is get Kdenlive working. Are you doing all of this on Slackware? if so, did you build Kdenlive from its SlackBuild or are you running it some other way?

Ffmpeg makes an allowance for filters, but I don't think frei0r has a chroma key / greenscreen filter.

For concatenating clips together, you can do that easily. Assuming the clips are exactly the length that you want them to be:

Code:

$ ffmpeg -i clip1.mov -i clip2.avi -acodec libvorbis -vcodec libxvid -threads 4 edited.mp4

Or similar. As you can see, we use two input flags to point to the two clips we want to concatenate, then define the audio codec and the video codec we want to use (use "copy" if both clips are already in the codec you want to end with), and then an output file.

If you need to trim the clips before concatenating, you can do that with the -ss and -t flags.

I would love to get KDEnlive working but as I explained in previous posts, I can't find a good source for all the dependencies.

I think I have a new problem regarding concatenating clips. Mostly I want to work with pretty short clips, some times just a few seconds. The problem is, I don't know how to ensure that I start with a key frame. If I don't then nothing will show until a key frame is reached which in a very short clip can be never. I have that problem with one experiment, I have a clip about 3 sec long and then I have the same clip but running in reverse and I want to put the two together. But when I do, I get nothing out, a 0 length file. Never a dull moment.

rdx · 05-12-2016, 06:41 AM

Quote:

Originally Posted by phil.K

I like to use melt. Openshot uses melt as a backend too.

You can preview a merge of two or more files by typing

Code:

melt *.mpg

You can also convert video files to another format and merge them at the same time as well.

Code:

melt 01.avi 02.avi -consumer avformat:output.mpg vcodec=mpeg1video b=1000k acodec=mp2 ab=128k -progress

The command converts the avi files to a merged mpeg1video file called output.mpg

This is just a scratch of this powerful command.

I tried

Code:

melt *.mpg

got an error, "failed to dlopen /usr/lib64/mlt/libmltsox.so". It's just one more example of packages that depend on too many others.

BW-userx · 05-12-2016, 07:20 AM

Quote:

Originally Posted by rdx

No, I do not. I simply thought it is easier. I have Blender installed but I can't figure it out, it seems very complicated. I looked at Kino and it says that project is dead. I installed AVIdemux but I haven't read the manual yet. So far it seems that KDEnlive comes closest to what I want but I am having NO LUCK getting help from them (I can't get logged into the forum). Something is wrong such that it isn't seeing the FFmpeg libs so it won't load video or audio clips (still pics, like jpeg, png, gif work fine).

From one tutorial I got a simple example of what I'm looking for, the filter syntax:
ffmpeg -i input.mp4 -vf hflip output.flv

But when I try other filters, especially those that require a parameter, I'm stuck. I tried, for instance:
ffmpeg -i input.mp3 -af aecho output.wav
and the delay was like a whole second or something, sounded weird.

Anyway, I'm still looking for a viable solution to what seems very basic video editing operations.

I thought that too until I went YouTube how to edit video in blender -- made it soo simple to do
here is video how toos series for blender 2.7x

Blender Video Editing

it takes you from basic set up to advance

you can import one format then render it out in many different formats sizes everything...
it is worth your time to check into it.

Keith Hedger · 05-12-2016, 09:52 AM

Quote:

Originally Posted by rdx

... it is not possible to do the overlay with ffmpeg ...

Not strictly true, this:

Code:

ffmpeg -i Russia-Helsinkii-Ferry.mpg -i out.mp4 -filter_complex "[0:0]scale=720:576[a];[1:0]scale=100:100[b];[a][b]overlay=100:50" -acodec copy   out.mpg

Will overlay two videos the bottom one is Russia-Helsinkii-Ferry.mpg the overlayed video is out.mp4, out.mp4 is scaled to 100x100 here:

Code:

... [1:0]scale=100:100[b] ...

And postioned on the main video at postion 100,50 (x,y) here:

Code:

... [a][b]overlay=100:50 ...

Audio is just copied 'as is'

rdx · 05-15-2016, 06:08 AM

Okay, I think I am ready to declare this issue solved. I now know that one can use the concat filter to combine clips in addition to simply using cat on .mpg files. I am convinced that chroma key is probably better done with other apps and I have found the "deshake" filter for ffplay to be a bit unstable.

I have tried to install KDEnlive as a better alternative but that failed due to missing dependencies. What I have found that works best is Blender. First, it installs and runs, a huge plus. Second, there are hours and hours of detailed tutorials on YouTube explaining how to use it in detail. I doubt I will ever know how to do everything blender can do but already I can do basic video editing and that was my original goal.

Thanks to everyone who posted, I found all the discussion helpful and especially specific links to detailed instructions. You have made this a rewarding experience.

Shadow_7 · 05-16-2016, 10:54 AM

The main issue with ffmpeg is that the commandline parameters are forever evolving. So once you think you know what you're doing, you have to relearn everything.