itproject-docs/highlight-pipeline-planning.org

* Highlight Generator Pipeline Planning

** Overview

[[file:~/downloads/highlightgeneration-process.svg]]

** Pipeline `API'

*** Input

User-driven selection of input videos.

 - files :: /user-selected/ list of ≥1 input files to be processed
 - (optional) time restriction :: start and end time (or: start time + duration?) of file to restrict highlight generation to (format: s & H:M:s ?) (see note)
 - (optional, /stretch/) feature extractor mapping :: a map of files to feature exactors, eg:

#+BEGIN_SRC yaml
video1:
    path: /video/directory/video1.mkv
    feature_extractors:
      - laughter-detection
      - loud-moments

video2:
    path: /video/directory/video2.mp4
    start: 10:00
    end: 50:00
    feature_extractors:
      - word-recognition
#+END_SRC

**** Time Restriction

To properly operate on a restricted range, this can create a temporary media file (using eg ffmpeg) for operation on by the *Feature Selection* step.

Creating a temporary file can be avoided by ensuring each /Feature Selector/ respects a custom duration, but since some are third-party they may need their implementation updated.

*Discussion point*: pros and cons of updating 3P feature selectors

**** Output

Conceptually, a list of files (either original path, or path to temporary time-restricted version) and associated options for each. This will either be a language-specific object, or the equivelent JSON.

Example:

#+BEGIN_SRC json
{
    source_videos: [
        { "path":  "/video/director/video1.mkv",
          "feature_extractors": [
              "laughter-detection",
              "loud-moments",
              ],
          },
        { "path": "/tmp/videohighlights/inputclip0001.mkv",
          "feature_extractors": [
              "word-recognition"
              ],
          }
    ]
}
#+END_SRC

**** Further Considerations

 - time specification formats -- start & end ? start & duration? either? negative times for specifying time distance from /end/ of file?

*** Source / Feature Selection

A ~Source~ is an automation-driven /method/ of figuring out what bits of an *input video* to keep.

**** Input

A ist of input videos as in *Input*

**** Options

 - ~Source~-specific /options/ (eg min duration, threshold etc for laughter-detection),
 - /working directory/
 - minimum duration (see /Further Considerations/)

**** Output

A set of ≥0 /Feature/-type objects or equivalent JSON.

**** Further Considerations

At time of writing the feature selection drivers conceptually output timestamps, as opposed to durations; but conceptually durations make more sense. It may be worthwhile to automatically promote any `point' timestamps to a duration.

Pros: makes the next step in the pipeline more uniform
Cons: will probably over-sample

Consequent consideration: does that mean we should let the user adjust the /pre-consolidation/ times too? Probably, but doing that it a UX-friendly way will potentially take some doing.

*** Consolidation

The consolidation stage takes a list of timestamps (across videos) and /consolidates/ / merges proximal times to create *clip definitions* across *sources*.

 - input :: a list of *video files* with associated *timestamps* or *time ranges* (and their sources), eg in JSON:

   #+BEGIN_SRC json
   { "videos": [ "/path/to/videos/video1.mp4": [ { "time": 180, "source": "laughter-detect" },
                                                 { "time": 187, "source": "laughter-detect" },
                                                 { "time": 295, "source": "loud-detect" },
                                                 { "time": 332, "source": "laughter-detect" }
                                                 ],
                 "/path/to/videos/video2.mp4": [ { "start": 45, "end": 130, "source": "segmenter" } ],
                 ]
     }
   #+END_SRC

**** Approach

The input list of feature times goes through comparison process: if a feature has /overlap/ with another (that is, starts or ends within the time period of another feature), those two features are consolidated into one. This comparison can be done with a /delta/, a small amount of time (eg 15s) for which `nearby' intervals can be considered overlapping.


**** Options

 - maximum delta between clips to be consolidated (default: 15s [rationale: Stetson-Harrison approach[fn:stetson])
 - maximum duration of a consolidated clip (default: 60s [rationale: max duration of YT shorts?])
 - maximum number of consolidated clips to output (default: unlimited)


[fn:stetson] The [[https://english.stackexchange.com/a/426717][Stetson-Harrison]] approach

*** Refinement

User-driven process of /selection/ and applying /operators/ to clips before final output.

**** 1. Selection

User choice of which clips to keep.

**** 2. Process

User applies (video) ~Processes~ to the clip(s):

 - duration :: select start and end time (possibly before/after generated clip's boundaries)
 - join :: further join clips which were not joined at consolidation stage
 - filters :: eg sharpen / slomo / (de)saturate etc [stretch]
 - split ::

*Note*: need to be careful not to reimplement an NLE here!

*** Highlights

Ultimate output.