Chime Media Concatenation Pipeline with different lengths for audio and video

I'm building an application using Chime and trying to concatenate the artifacts are the current issue I found.

If I'm using the video with active audio speaker then the concatenation works ok, since the audio and video files are the same.

But, if we start using separate video and audio files (in this case, we set for one specific attendee to be recorded, instead of everyone speaking), then the media concatenation pipeline produces two artifacts, one for audio and one for video, of different lengths, for example, if one of the attendees turn of his camera for a while.

I'd like to know if the media concatenation pipeline has any solution for that, like inserting blank frames in the video whenever there is no video being captured. And if there is nothing, if there is any directions for how can I concatenate myself these different artifacts to create a synced video.