Change vcodec before -i

[EliasDeVos]

Q	A
Bug?	yes
New Feature?	no
Version Used	0.9.5
FFmpeg Version	FFmpeg and version
OS	mac os mojave

Actual Behavior

Right now it is not possible to change a video codec before opening a file

Expected Behavior

For my use case i need to get the alpha layer of a webm file. for this i need to add this before the file gets opend: -vcodec libvpx-vp9

Steps to Reproduce

All the time

Possible Solutions

So right now in 0.9.5 (and also in master) you can only apply filters after the -y -i {path} option
see here and here

but for me if i execute this ffmpeg -i mov_ffmpeg.webm -f mp4 -vcodec libx264 -preset fast -profile:v main -acodec aac -vf “split[a][b];[a]pad=iw:ih*2[src];[b]alphaextract[filt];[src][filt]overlay=0:h” test.mp4 without -vcodec libvpx-vp9 before the -i throws an error (because my webm's are vp9 and not vp8.

Any suggestions on this ? or maybe i can create a pull request for this if you want this fixed ?
or you don't see this as an issue ? let me know

[jens1o]

I'm sorry for the late reply, I was disconnected from the Internet, because my new ISP wasn't able to set-up my connection properly.

I actually like this idea. This is also already (partly) implemented in the upcoming version branch. I want to make it possible to insert custom filters at truly any location through filters(#464). This would also fix your problem. Let us keep it open still. :)

[throttlehead]

I actually like this idea. This is also already (partly) implemented in the upcoming version branch. I want to make it possible to insert custom filters at truly any location through filters(#464). This would also fix your problem. Let us keep it open still. :)

The library definitely needs this option!!! I'm using opus pretty heavily in my application and need to be able to set '-acodec libopus' in the ffmpeg command to properly transcode to AAC with fewer audio issues.

After digging through the code I was thinking the easiest way to implement would be to a '->setInitialParams()' method that would be used when forming the base command with '->basePartOfCommand()'.

For now I'm going to sideline using the library for this and just running custom ffmpeg commands but please consider this feature!

[Romain]

Solved with PR #703