TL;DR: most of the time
Yes. There is passthrough playback during the ingest process. So whichever file is being used for the source of your video will be used while our system optimizes and distributes out the device specific encodes. This means videos from YouTube, Vimeo, WordPress Media Library, or most any other source with a publicly viewable video should playback before SmartVideo has optimized the video.
If you are not seeing video playback at all during this optimization process, then it could be one of two things:
1. The most likely reason is that the original video file is not encoded in a format that allows for effective web delivery. In a way, this is the reason that a service like ours is necessary because it's really hard to get video properly encoded for web-based delivery. That doesn't help you during the optimization process of course, but until we optimize it, that video file is just not in a great format for streaming.
2. The other possible reason could be if your source URL is prohibited from being used to transmit video. This would be very unlikely unless you were using a storage provider like Dropbox or Google Drive for your source content. If you are using a public URL for your videos, this is probably not the reason. It's most likely reason #1.
If your video takes a long time, but eventually begins playback, see reason #1. If the video never starts playing, then it's probably due to reason #2.