From fc084d0b624529b8e6b0505c3ed1cc41f45006ff Mon Sep 17 00:00:00 2001
From: Ruslan Ermilov <ru@nginx.com>
Date: Thu, 15 Sep 2011 08:59:13 +0000
Subject: [PATCH] Added ngx_http_mp4_module documentation.

---
 docs/GNUmakefile                      |   3 +-
 docs/xml/http/ngx_http_mp4_module.xml | 156 ++++++++++++++++++++++++++
 2 files changed, 158 insertions(+), 1 deletion(-)
 create mode 100644 docs/xml/http/ngx_http_mp4_module.xml

diff --git a/docs/GNUmakefile b/docs/GNUmakefile
index 5cc995fef..ebd8332e7 100644
--- a/docs/GNUmakefile
+++ b/docs/GNUmakefile
@@ -58,7 +58,8 @@ docs/xslt/changes.xslt:		docs/xsls/changes.xsls
 
 html:									\
 	docs/html/ngx_core_module.html					\
-	docs/html/http/ngx_http_core_module.html
+	docs/html/http/ngx_http_core_module.html			\
+	docs/html/http/ngx_http_mp4_module.html
 
 docs/html/%.html:							\
 		docs/xml/%.xml						\
diff --git a/docs/xml/http/ngx_http_mp4_module.xml b/docs/xml/http/ngx_http_mp4_module.xml
new file mode 100644
index 000000000..d3332d32f
--- /dev/null
+++ b/docs/xml/http/ngx_http_mp4_module.xml
@@ -0,0 +1,156 @@
+<?xml version="1.0"?>
+
+<!DOCTYPE module SYSTEM "../../dtd/module.dtd">
+
+<module name="HTTP MP4 Module" id="http_mp4_module">
+
+<section name="Summary">
+
+<para>
+The module <code>ngx_http_mp4_module</code> provides pseudo-streaming
+server-side support for H.264/AAC files typically having filename extensions
+<pathname>.mp4</pathname>, <pathname>.m4v</pathname>,
+and <pathname>.m4a</pathname>.
+</para>
+
+<para>
+Pseudo-streaming works in alliance with conformant Flash players.
+A player sends an HTTP request to the server with a start time
+argument in the request URI’s query string (named simply
+<parameter>start</parameter>
+and specified in seconds), and the server responds with a stream
+so that its start position corresponds to the requested time,
+for example:
+<example>
+http://example.com/elephants_dream.mp4?start=238.88
+</example>
+This allows for a random seeking at any time, or starting playback
+in the middle of a timeline.
+</para>
+
+<para>
+To support seeking, H.264-based formats store the metadata
+in the so-called “moov atom.”
+It is a part of the file that holds the index information for the
+whole file.
+</para>
+
+<para>
+To start playback, a player first needs to read metadata.
+This is done by sending a special request with the
+<parameter>start=0</parameter>
+argument.  Many encoding software will insert the metadata at
+the end of the file.  This is bad for pseudo-streaming:
+the metadata needs to be located at the beginning of the file,
+or else the entire file will have to be downloaded before it
+starts playing.  If a file is well-formed (with metadata at the
+beginning of a file), nginx just sends back the contents of a file.
+Otherwise, it has to read the file and prepare a new stream so that
+metadata comes before media data.
+This involves some CPU, memory, and disk I/O overhead,
+so it is a good idea to
+<link url="http://flowplayer.org/plugins/streaming/pseudostreaming.html#prepare">
+prepare an original file for pseudo-streaming</link>,
+rather than having nginx do this on every such request.
+</para>
+
+<para>
+For a matching request with a non-zero
+<parameter>start</parameter>
+argument, nginx will read metadata from the file, prepare the
+stream starting from the requested offset, and send it to a client.
+This has the same overhead as described above.
+</para>
+
+<para>
+If a matching request does not include the
+<parameter>start</parameter>
+argument, there is no overhead, and the file is just sent as a static resource.
+Some players also support byte-range requests, and thus do not require
+this module at all.
+</para>
+
+<para>
+This module is not built by default, it should be enabled with the
+<command>--with-http_mp4_module</command>
+configuration parameter.
+<note>
+If you were using the third-party mp4 module, be sure to disable it.
+</note>
+</para>
+
+<para>
+A similar pseudo-streaming support for FLV files is provided by the module
+<link doc="ngx_http_flv_module.xml">ngx_http_flv_module</link>.
+</para>
+
+</section>
+
+
+<section id="example" name="Example Configuration">
+
+<para>
+<example>
+location /video/ {
+    mp4;
+    mp4_buffer_size     1m;
+    mp4_max_buffer_size 5m;
+}
+</example>
+</para>
+
+</section>
+
+
+<section id="directives" name="Directives">
+
+<directive name="mp4">
+<syntax>mp4</syntax>
+<default/>
+<context>location</context>
+
+<para>
+Turns on module processing in a surrounding location.
+</para>
+
+</directive>
+
+
+<directive name="mp4_buffer_size">
+<syntax>mp4_buffer_size <argument>size</argument></syntax>
+<default>mp4_buffer_size 512K</default>
+<context>http</context>
+<context>server</context>
+<context>location</context>
+
+<para>
+Sets the initial size of a memory buffer used to process MP4 files.
+</para>
+
+</directive>
+
+
+<directive name="mp4_max_buffer_size">
+<syntax>mp4_max_buffer_size <argument>size</argument></syntax>
+<default>mp4_max_buffer_size 10M</default>
+<context>http</context>
+<context>server</context>
+<context>location</context>
+
+<para>
+During metadata processing, a larger buffer may become necessary.
+Its size cannot exceed the specified <argument>size</argument>,
+or else nginx will return the server error
+<http-status code="500" text="Internal Server Error"/>,
+and log the following:
+<example>
+"/some/movie/file.mp4" mp4 moov atom is too large:
+12583268, you may want to increase mp4_max_buffer_size
+</example>
+</para>
+
+</directive>
+
+</section>
+
+</module>