Support for Matches

[atgeller]

Instead of keeping a list of phrases, it would be nice to have a notion of a match, which would hold the list for each channel. This would also then support writing metadata to a file, which could then be loaded to playback a previous recorded match, and export it to a single MP4 via ffmpeg in the command line.

Having a representation of a match, starting and ending it, and writing the metadata should be straightforward. The "difficult" part will likely be implementing a file interface to open old matches for playback.

[atgeller]

Currently, there's relevant metadata being stored in both the PhraseRecording and Match objects (I think due to convergent evolution). I think that PhraseRecording should only contain data specific to that channel's recording, and not more general information. Then, the channel should defer to the match for that metadata instead, since it will be common to all channels. I'll update that in #15 and feature/tags.

[alan-geller]

Once we unify the metadata, we should figure out how we want to save everything. I can think of three options:

• A separate MPEG file for each camera, plus a metadata save file in JSON or YAML. This is nice and simple.
• One MPEG file with multiple streams, one for each camera, and with the match metadata stored in the MPEG file header. The advantage of this option is that it keeps everything for a match in one file; in the other model you have to deal with multiple files and so the possibility of missing parts. I'm not sure that you can easily stream video to a multi-stream MPEG file, though...
• A ZIP file that holds the separate files from option two. This avoids the multiple file issue at the cost of a performance hit both reading and writing and some added complexity.

It's also possible to have a kind of hybrid, where while recording all of the files are kept separate, and on some "Save Match" command the files are grouped together into a single container, whether an MPEG file or a ZIP file.

In all models we'd need to add support for opening and viewing a saved match from the app.

[atgeller]

I got started looking into this but it turns out the current Match class isn't actually used anywhere and I wasn't sure how to go about changing that,

[atgeller]

I did put some thinking into the set-up and decided on the following, but it's a bit arbitrary.

• The Match class will hold metadata that is not accessed during playback: whether the replay is tagged, and what the trigger was.
• Other metadata used for playback will be stored in the PhraseRecording class, as is done now, to remain easily accessible during playback.
• The Match class will be responsible for tracking the index of the phrase currently being replayed (the index among the history of actions). I imagine this working as follows: on a playback event, the VideoGridManager will first send the request to the Match, if the playback event is one that updates the currently replaying action, then the Match class should return the currently replaying action index (perhaps -1 if a different event to then be sent to the channels, and I32.MAX if live).
• When saving a Match, it will collect all of the PhraseRecordings from the VideoChannels. This would probably be better implemented by having the Match hold a dictionary mapping the VideoChannel name to the same list that the VideoChannel uses, so it gets updated automatically.

The downside to this approach is that every time the cameras change the Match would have to be restarted. An altrernative approach that would address this is to store a mapping like above per Phrase instead of for all Phrases, but this raises the issue of how such Phrases would get collected.