--only-hash option for
ipfs add along with whichever other add options you think are appropriate (e.g.,
--trickle for video). For example,
ipfs add --only-hash path/to/file
If the following command returns something, then there are other peers that say they can provide the root hash. Note that this doesn't necessarily mean they can provide the entire DAG. For example, some of the nodes might have the root node of the DAG and the first part of a video file.
ipfs dht findprovs hash