[modeless]

Ah, so all the frames for every strip are interleaved in your container, and you just read sequentially and ignore the frames you don't need? That's probably the right thing for local videos.

I had each gop in a separate file like HLS or DASH (except for the background which was a single file also containing the audio track). It's unwieldy but makes HTTP streaming a little simpler because you don't need range requests or an index.

Also, instead of bitstream hacking to stitch three strips into one, I encoded multiple strips into "pre-stitched" views. This means that every strip is encoded redundantly in multiple views, bloating the on-disk video size. But for streaming that only affects the server, not the client, and it's nice for the client to only download/decode one view at a time (plus the background) instead of three strips. Bitstream hacking to join the strips would definitely be better if it can work, though.