Hot to enable timeline preview images in Paella Player?

[scharnknhft]

Hi all,

I'm trying to get timeline previews to work in our Opencast cluster as described in the Paella Player documantation.

I confirmed that the grid image is generated and can be opened manually. It's also referenced in the video manifest JSON file when opening a video (under the attachments section).

 {
    "id": "56919f15-ba9e-462d-8c93-ad9629004559",
    "type": "presenter/timeline+preview",
    "ref": "track:5b151a19-9643-405a-a97b-159e69c88dcf",
    "mimetype": "image/png",
    "tags": {
        "tag": "engage-download"
    },
    "url": "https://XXX/static/mh_default_org/engage-player/c4e0437c-1e91-4bb5-b84c-de7f1f34febf/76c6ca65-aebc-4105-a8ed-ca1cc87cff57/opencast-test-presenter_short_476428fd-3a65-469a-a497-07a95b5c8286_timelinepreviews.png",
    "additionalProperties": {
        "property": [
            {
                "key": "resolutionY",
                "$": "-1"
            },
            {
                "key": "imageCount",
                "$": "100"
            },
            {
                "key": "resolutionX",
                "$": "160"
            },
            {
                "key": "imageSizeY",
                "$": "10"
            },
            {
                "key": "imageSizeX",
                "$": "10"
            }
        ]
    }
}

However, when I hover over the timeline, nothing happens. From what I understand, there should be a popup showing the appropriate timeline preview image.

I noticed that the Paella Player docs specify to put the grid image in the metadata section of the video manifest. However, with Opencast, it is found under 'attachments'. Could this be the issue?

Any pointers are much appreciated!

Katrin

[mtneug]

The metadata section refers to the Paella Player data object. The metadata vs attachment usage refers to the mediapackage model from Opencast. Putting the images in the attachment section within the mediapackage is correct. IIRC, metadata elements in Opencast can only be XML or JSON files.

If the image file is generated but not shown in Paella Player, it is either a problem in the mapping of the two data models (Opencast mediapackage -> Paella data JSON) or maybe a plugin is not enabled.

[scharnknhft]

Thank you for the detailed explanation.

In Opencast the image file is published as "presenter|presentation/timeline+preview"

  # Generate timeline preview images
  - id: timelinepreviews
    if: ${presenter_work_video} OR ${presentation_work_video}
    fail-on-error: false
    exception-handler-workflow: partial-error
    description: Creating timeline preview images
    configurations:
      - source-flavors: presenter/trimmed,presentation/trimmed
      - target-flavor: '*/timeline+preview'
      - target-tags: engage-download
      - image-count: 100

which is also how it's referenced in the Paella Player config:

   "opencast": {
...
            "timelineAttachmentsFlavours": [
                "presentation/timeline+preview",
                "presenter/timeline+preview"
            ],
...
    },

so from my understanding the mapping between the two should be correct.

I'm not sure which plugins to enable since neither the Opencast nor the Paella documentation mentions anything about it. I tried searching for working examples online that use timeline previews to check their config.json files, but I couldn't find any (including on the Opencast and Paella demo servers).

I'm starting to think either something is wrong with my browser or I might have misunderstood what the timeline previews are supposed to do.

[geichelberger]

Currently, the timeline preview is only shown if a chapter or segment exists. polimediaupv/paella-player#68

[snoesberger]

In our installation, we cannot see the previews, even though some segments exist. Using the browser development tools, I can see that the timeline preview images are loaded, but they are not shown in the player.
I can see the same behavior on the Paella player demo page: https://paellaplayer.webs.upv.es/examples/ or https://paellaplayer.webs.upv.es/player/dual-stream-f-t-c, timeline preview images are loaded but not shown. So, to me this looks like a Paella player bug.

[gregorydlogan]

Given that we've seen some releases with updated Paella players, is this still unresolved?

[snoesberger]

In the meantime there is a fix: polimediaupv/paella-player@78a49bf

However, I don't believe the fix has been included in a new Paella player release yet. At least, the problem still exists on the Paella demo page: https://paellaplayer.webs.upv.es/examples/