October 2024
Intermediate
240 pages
6h 57m
Japanese
Content preview from 図解まるわかり VR・AR・MRのしくみ
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102
HTTPライブストリーミング、MPEG-DASH
効率的な映像配信技術
5-9
HTTPライブストリーミングのしくみ
さまざまな体験を提供するXRには、高いレベルでの描写能力が求めら
れます。そのような映像体験をリアルタイムで実現させるためには、効率
的な映像配信技術が必要です。
現在、インターネットを通じた動画配信は頻繁に行われていますが、そ
の根底には、HTTPライブストリーミング（HLS）や MPEG-DASH と
呼ばれる技術があります。
HTTPライブストリーミングは、iPhoneなどを手掛けるApple社が独自
開発した規格です（図5-17）。すでに多くのWebブラウザ上で使用されて
おり、国内のライブ配信サービスにも活用されています。
配信する動画を秒単位に区切ったセグメントファイルを複数用意し、そ
れらを再生する順番や時間を決めたインデックスファイルを用意すること
で動画配信を実施します。
特別なソフトを必要とせず、通常のWeb環境で動画が視聴できるため、
幅広いシーンで使える汎用性の高い技術なのです。
MPEG-DASHの適応型ストリーミング
MPEG-DASHは、適応型ストリーミングという視聴者の通信環境に合わ
せて、最適な画質や解像度の動画を自動的に選択して配信する技術の国際
標準規格です（図5-18）。動画をセグメントに分割し、視聴者の通信環境
に合わせて最適なビットレートの動画を選択して配信することができま
す。
これにより、通信環境が悪い場合でも途切れにくく、高品質な動画配信
が
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.