HTTP 自適性串流技術(HTTP Adaptive Streaming, HAS) 是目前被廣泛使用
的串流技術之一，其將原始影片編碼成不同品質的影像，並切割成許多視訊片段
(Video Segment)，播放程式便可依據網路頻寬，選擇適切的品質並下載對應的視
訊片段，避免因網路頻寬不足而造成的播放遲滯。由於影片被切成許多短暫的片
段，客戶端(Client) 播放程式必須頻繁發送HTTP 請求以下載視訊片段，造成許
多額外的負荷(Overhead)，如何降低這負荷是目前各方極欲解決的問題。於是，
本論文提出一種新穎的伺服器推送(Server Push) 方式，其利用HTTP/2 中新增
的伺服器推送，搭配伺服器端配速(Server Pacing) 機制，傳輸所有的視訊片段；
另外，藉由將位元速率自適(Bitrate Adaptation) 機制移往伺服器端，以避免在嚴
苛網路環境下切換位元速率時屬於舊位元率伺服器推送資料流(Stream) 與屬於新
位元率資料流之頻寬競爭與頻寬浪費(Bandwidth Wastage)；透過複雜度分析可
知，我們所提出的推送方式並未在時間及空間上有過多之負荷；除此之外，我們
亦於MPEG-DASH (Dynamic Adaptive Streaming over HTTP) 架構下，實做本碩
士論文所提出之推送方式，並與相近文獻所提出之推送策略(Push Strategy) 相
比較。經由模擬結果得知，我們所提出的推送方式能成功地降低HTTP 請求數量
到一次，且在嚴苛的網路環境下也能較相近文獻有更高的平均位元速率(Average
Bitrate)，並大幅降低影像播放遲滯。

The HTTP adaptive streaming (HAS) is one of the widely-used streaming
protocols. By encoding video files at different quality levels and then segmenting
them into video segments, video segments can be downloaded by a streaming
client once the quality level is properly selected according to the network bandwidth
to avoid playback stalls. Because a video file is segmented into numerous
segments, a streaming client has to explicitly send HTTP requests to download
video segments, bringing a significant overhead. How to remove the overhead
properly then forms the issue to be solved by a lot of related work. Aiming at
this goal, we propose a novel approach by using the HTTP/2 server push along
with the technique of server pacing to deliver video segments. In addition, we
move the load of bitrate adaptation to the server to avoid bandwidth competition
and bandwidth wastage caused by bitrate switching when the bandwidth is throttled
severely. Through complexity analysis, we show that no significant overhead
is brought by our proposed approach. Furthermore, a prototype of our proposed
approach is built upon the MPEG dynamic adaptive streaming over HTTP (MPEGDASH)
architecture and compared with the closely related push strategies. Via
simulations, we show that our proposed approach can limit the number of HTTP
requests to one and outperform the closely related push strategies in the literature
in terms of average achievable bitrate and number of playback stalls when a
harsh network condition occurs.

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