I’d test to make sure that sqllite can feed you the audio / video data back to you fast enough. Also, having one big file with everything might make maintenance and updates difficult - change one piece of audio and you have to redeploy the whole database.
You might want to use a sqllitedb as the index (since it’ll just be relative paths, it’ll be small) and to cache metadata. Have the records there to point to actual file assets in the file system (and break them up so you don’t have more than a couple hundred or a thousand in each directory). I’d measure that too to see if large directory contents affect file opening speed.
As far as the actual audio or video format, I have no idea on what’s optimal cross-platform, especially in terms of ultimate use - I’m just a file system monkey