More writing, citations, fix references

src/state-of-the-art/video.tex

@@ -2,8 +2,8 @@
 
 \section{Video scenario}
 
-Despite what one may think, the video streaming scenario and the 3D streaming one share many similarities: at a higher level of abstraction, they are both interfaces that allow a user to access remote content without having to wait until everything is loaded.
-Analyzing the similarities and the differences between the video and the 3D scenarios as well as having knowledge about video streaming litterature are key to developing an efficient 3D streaming system.
+Despite what one may think, the video streaming scenario and the 3D streaming one share many similarities: at a higher level of abstraction, they are both systems that allow a user to access remote content without having to wait until everything is loaded.
+Analyzing the similarities and the differences between the video and the 3D scenarios as well as having knowledge about video streaming litterature is\todo{is key or are key?}  key to developing an efficient 3D streaming system.
 
 \subsection{Similarities and differences between video and 3D}
 
@@ -91,29 +91,31 @@ Finally, most of the other interfaces will give at least 5 degrees of freedom to
 \subsection{DASH\@: the standard for video streaming}
 
 \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.
+Dynamic Adaptive Streaming over HTTP (DASH), or MPEG-DASH~\cite{dash-std,dash-std-2}, is now a widely deployed
+standard for streaming adaptive video content on the Web~\cite{dash-std-full}, 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.
 
+\subsubsection{DASH 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}
+\paragraph{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}
+\paragraph{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}
+\paragraph{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}
+\paragraph{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.
@@ -126,4 +128,40 @@ Once a video is encoded in DASH format, once the files have been structured and
 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{DASH-SRD}
 
+DASH-SRD (Spatial Relationship Description,~\cite{dash-srd}) is a feature that extends the DASH standard to allow stream only a spatial subpart of a video to a device.
+It works by encoding a video at multiple resolutions, and tiling the highest resolutions, that way, a client can choose to download either the low resolution of the whole video or higher resolutions of a subpart of the video (see Figure~\ref{sota:srd-png}).
+For each tile of the video, an adaptation set is declared in the MPD, and a supplemental property is defined in order to give the client information about the file.
+This supplemental property contains many elements, but the most important ones are the position ($x$ and $y$) and the size (width and height) of the tile describing the position of the tile in relation to the full video. An example of such a property is given in Listing~\ref{sota:srd-xml}.
+
+Essentially, this feature is a way of achieving view-dependent streaming, since the client only displays a part of the video and can avoid downloading content that will not be displayed.
+This is especially interesting in the context of 3D streaming since we have this same pattern of a user viewing only a part of a content.
+
+\begin{figure}[th]
+    \centering
+    \includegraphics[width=\textwidth]{assets/state-of-the-art/video/srd.png}
+    \caption{DASH-SRD~\cite{dash-srd}\label{sota:srd-png}}
+\end{figure}
+
+\begin{figure}[th]
+\lstinputlisting[%
+        language=XML,
+        caption={MPD of a video encoded using DASH-SRD},
+        label=sota:srd-xml,
+        emph={%
+            MPD,
+            Period,
+            AdaptationSet,
+            Representation,
+            BaseURL,
+            SegmentBase,
+            Initialization,
+            Role,
+            SupplementalProperty,
+            SegmentList,
+            SegmentURL,
+            Viewpoint
+        }
+    ]{assets/state-of-the-art/video/srd.xml}
+\end{figure}