StoryMaker™

An important distinction Nathan, the cross fade should only apply to the audio of the video clip. Crossfading the picture from one clip to another is unnecessary.

We were simply trying to make sure we had the functionality for both audio to audio fading as well as video to video. But, it is not necessary for the video in the clips to have a visual crossfade, only an audio one.

n8fr8 wrote:

Working on crossfades this week, based on this concept:
http://nerdcore-enthusiasm.blogspot.com/2010/05/crossfade-two-videos-clips-from-command_340.html

Thanks for the clarification. We will focus then on "sox" which is an open-source command line audio processer that has all the fx we need.

There is an existing project for running on Android (https://github.com/Kyborg2011/SoxPlayer) though we may want to just create our own build from scratch. TBD!

So in order for there to be audio cross-fades, there needs to be separate audio tracks that are cut 1 second before the video and 1 second after the video. This is needed so that the audio tracks overlap when combined, and then can therefore be crossfaded. Is there already infrastructure in place for working with the audio tracks separately than video?

And I'll second Nathan in that I think you cannot do fades/cross-fades with ffmpeg as it stands now. So our options are either use sox or I can also easily write a 'afade' filter for ffmpeg. I think that having an 'afade' plugin for ffmpeg will be the more manageable option in the long run, while using sox will probably be the quickest route to getting something working.

hans wrote:

So in order for there to be audio cross-fades, there needs to be separate audio tracks that are cut 1 second before the video and 1 second after the video. This is needed so that the audio tracks overlap when combined, and then can therefore be crossfaded. Is there already infrastructure in place for working with the audio tracks separately than video?

Are you talking about in the java wrapper or in ffmpeg? In Java, not yet. But in ffmpeg we can easily split out audio video tracks into separate files.

And I'll second Nathan in that I think you cannot do fades/cross-fades with ffmpeg as it stands now. So our options are either use sox or I can also easily write a 'afade' filter for ffmpeg. I think that having an 'afade' plugin for ffmpeg will be the more manageable option in the long run, while using sox will probably be the quickest route to getting something working.

No comment here, Nathan?

I've ported sox to android inside android-ffmpeg. While this might be less than ideal, but we're in a time crunch and since sox depends on ffmpeg, this was the easiest solution.

Furthermore, I've integrated it into android-ffmpeg-java. I only implemented the bare minimum needed to serve our needs: simple crossfade.

Pull requests are out for each repo:

• https://github.com/guardianproject/android-ffmpeg/pull/2
• https://github.com/guardianproject/android-ffmpeg-java/pull/4

I also pushed the Android Test Project I used.