单个画布上多个音视频文件的目录

翻译：羊牧东岭

原文地址：https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/

用例

将音视频内容拆分为多个文件是很常见的做法。本专题展示了如何使用单个画布 (Canvas) 对此类内容进行建模。使用单个画布的好处是跨文件连续播放，浏览器可以显示这些文件的总的持续时间，从而为用户提供一种聚合性的观看收听体验。

实施说明

本例的实现基于音视频内容的目录，但会使用两个视频文件，分别作为示例歌剧的每一幕，并注释在同一画布上：Atto Primo 指向 #t=0，而 Atto Secondo 指向 #t=3971.24 （紧接在 Atto Primo 结束之后），从而确保二者能连续播放。将歌剧的两幕作为注释包含在同一个注释页面上，从概念上讲更有意义，因为它们都指向同一画布。

这部歌剧涵盖了画布的整个长度，并为两幕而划分为两个范围 (Range)。Atto Primo 为前奏曲和第一曲提供了一个范围 (Range)，然后为该幕的其余部分提供了另一个范围 (Range)。为简单起见，未将 Atto Secondo 部分予以细分。

为展示更多上下文环境，例子中添加了元数据和缩略图属性。这里的实现类似于书籍的章节，但嵌套可能更深。

例子

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{
  "@context": "http://iiif.io/api/presentation/3/context.json",
  "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/manifest.json",
  "type": "Manifest",
  "label": {
    "it": [
      "L'Elisir D'Amore"
    ],
    "en": [
      "The Elixir of Love"
    ]
  },
  "metadata": [
    {
      "label": {
        "en": [
          "Date Issued"
        ]
      },
      "value": {
        "en": [
          "2019"
        ]
      }
    },
    {
      "label": {
        "en": [
          "Publisher"
        ]
      },
      "value": {
        "en": [
          "Indiana University Jacobs School of Music"
        ]
      }
    }
  ],
  "items": [
    {
      "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1",
      "type": "Canvas",
      "width": 1920,
      "height": 1080,
      "duration": 7278.422,
      "items": [
        {
          "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1/annotation_page/1",
          "type": "AnnotationPage",
          "items": [
            {
              "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1/annotation_page/1/annotation/1",
              "type": "Annotation",
              "motivation": "painting",
              "target": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1#t=0,3971.24",
              "body": {
                "id": "https://fixtures.iiif.io/video/indiana/donizetti-elixir/vae0637_accessH264_low_act_1.mp4",
                "type": "Video",
                "format": "video/mp4",
                "height": 1080,
                "width": 1920,
                "duration": 3971.24
              }
            },
            {
              "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1/annotation_page/1/annotation/2",
              "type": "Annotation",
              "motivation": "painting",
              "target": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1#t=3971.24",
              "body": {
                "id": "https://fixtures.iiif.io/video/indiana/donizetti-elixir/vae0637_accessH264_low_act_2.mp4",
                "type": "Video",
                "format": "video/mp4",
                "height": 1080,
                "width": 1920,
                "duration": 3307.22
              }
            }
          ]
        }
      ],
      "thumbnail": [
        {
          "id": "https://fixtures.iiif.io/video/indiana/donizetti-elixir/act1-thumbnail.png",
          "type": "Image"
        }
      ]
    }
  ],
  "structures": [
    {
      "type": "Range",
      "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/range/1",
      "label": {
        "it": [
          "Gaetano Donizetti, L'Elisir D'Amore"
        ]
      },
      "items": [
        {
          "type": "Range",
          "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/range/2",
          "label": {
            "it": [
              "Atto Primo"
            ]
          },
          "items": [
            {
              "type": "Range",
              "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/range/3",
              "label": {
                "it": [
                  "Preludio e Coro d'introduzione – Bel conforto al mietitore"
                ]
              },
              "items": [
                {
                  "type": "Canvas",
                  "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1#t=0,302.05"
                }
              ]
            },
            {
              "type": "Range",
              "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/range/4",
              "label": {
                "en": [
                  "Remainder of Atto Primo"
                ]
              },
              "items": [
                {
                  "type": "Canvas",
                  "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1#t=302.05,3971.24"
                }
              ]
            }
          ]
        },
        {
          "type": "Range",
          "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/range/5",
          "label": {
            "it": [
              "Atto Secondo"
            ]
          },
          "items": [
            {
              "type": "Canvas",
              "id": "https://iiif.io/api/cookbook/recipe/0064-opera-one-canvas/canvas/1#t=3971.24,7278.422"
            }
          ]
        }
      ]
    }
  ]
}

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