More curves, more intro

src/dash-3d/introduction.tex

@@ -1,43 +1,3 @@
-\fresh{}
-
-\section{A detour by DASH for video}
-\copied{}
-Dynamic Adaptive Streaming over HTTP (DASH), or MPEG-DASH~\cite{stockhammer2011dynamic,Sodagar2011}, is now a widely deployed
-standard for streaming adaptive video content on the Web~\cite{dashstandard}, made to be simple and scalable.
-\fresh{}
-DASH is based on a clever way of structuring the content that allows a great adaptability during the streaming without requiring any server side computation.
-
-\subsection{Content structure}
-All those pieces are structured in a Media Persentation Description (MPD) file, written in the XML format.
-This file has 4 layers, the periods, the adaptation sets, the representations and the segments.
-Each period can have many adaptation sets, each adaptation set can have many representation, and each representation can have many segments.
-
-\subsubsection{Periods}
-Periods are used to delimit content depending on the time. It can be used to delimit chapters, or to add advertisements that occur at the beginning, during or at the end of a video.
-
-\subsubsection{Adaptation sets}
-Adaptation sets are used to delimit content depending of the format.
-Each adaptation set has a mime-type, and all the representations and segments that it contains share this mime-type.
-In videos, most of the time, each period has at least one adaptation set containing the images, and one adaptation set containing the sound.
-
-\subsubsection{Representations}
-The representation level is the level DASH uses to offer the same content at different levels of resolution.
-For example, a adaptation set containing images have a representation for each available resolution (it might be 480p, 720p, 1080p, etc\ldots).
-This allows a user to choose its representation and change it during the video, but most importantly, since the software is able to estimate its downloading speed based on the time it took to download data in the past, it is able to find the optimal resolution, being the highest resolution that arrives on time to avoid stalling.
-
-\subsubsection{Segments}
-Until this level of the MPD, content can be long.
-For example, a representation of images of a chapter of a movie can be heavy and long to download.
-However, downloading heavy files is not suitable for streaming because it prevents the dynamicity of it: if the user requests to change the level of resolution of a video, the system would either have to wait until the file is totally downloaded, or cancel the request, making all the progress done unusable.
-
-Segments are used to prevent this behaviour. They typically encode files that last approximately one second of video, and give the software a great ability to dynamically adapt to the system. If a user wants to seek somewhere else in the video, only one second of data can be lost, and only one second of data has to be downloaded for the playback to resume.
-
-\subsection{Client side computation}
-
-Once a video is encoded in DASH format, once the files have been structured and the MPD has been generated, they can simply be put on a static HTTP server that does no computation other than serving files when it receives requests.
-All the intelligence and the decision making is moved to the client side.
-A client typically starts by downloading the MPD file, and then proceeds on downloading segments of the different adaptation sets that he needs, estimating itself its downloading speed and choosing itself whether it needs to change representation or not.
-
 \subsection{On our way to DASH-3D}
 
 DASH is made to be format agnositic, and even though it is almost only applied for video streaming nowadays, we believe it is still suitable for 3D streaming. Even though periods are not much of a use in the case of a scene that doesn't evolve as time goes by, but adaptation sets allow us to separate our content between geometry and textures, and gives answers to the questions that were addresed in the conclusion of the previous chapter.