Mercurial > hg > nginx-site
annotate xml/en/docs/http/ngx_http_mp4_module.xml @ 957:6d9d4bb571a9
Text review of the ngx_core_module.
author | Egor Nikitin <yegor.nikitin@gmail.com> |
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date | Sat, 08 Jun 2013 20:55:52 +0400 |
parents | 488a3f738db0 |
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22 | 1 <?xml version="1.0"?> |
2 | |
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3 <!-- |
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4 Copyright (C) Nginx, Inc. |
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5 --> |
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6 |
22 | 7 <!DOCTYPE module SYSTEM "../../../../dtd/module.dtd"> |
8 | |
89 | 9 <module name="Module ngx_http_mp4_module" |
22 | 10 link="/en/docs/http/ngx_http_mp4_module.html" |
589 | 11 lang="en" |
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12 rev="2"> |
22 | 13 |
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14 <section id="summary"> |
22 | 15 |
16 <para> | |
271 | 17 The module <literal>ngx_http_mp4_module</literal> provides pseudo-streaming |
22 | 18 server-side support for H.264/AAC files typically having filename extensions |
148
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19 <path>.mp4</path>, <path>.m4v</path>, and <path>.m4a</path>. |
22 | 20 </para> |
21 | |
22 <para> | |
88 | 23 Pseudo-streaming works in alliance with conforming Flash players. |
22 | 24 A player sends an HTTP request to the server with a start time |
25 argument in the request URI’s query string (named simply | |
271 | 26 <literal>start</literal> |
22 | 27 and specified in seconds), and the server responds with a stream |
28 so that its start position corresponds to the requested time, | |
29 for example: | |
30 <example> | |
31 http://example.com/elephants_dream.mp4?start=238.88 | |
32 </example> | |
33 This allows for a random seeking at any time, or starting playback | |
34 in the middle of a timeline. | |
35 </para> | |
36 | |
37 <para> | |
38 To support seeking, H.264-based formats store the metadata | |
39 in the so-called “moov atom.” | |
40 It is a part of the file that holds the index information for the | |
41 whole file. | |
42 </para> | |
43 | |
44 <para> | |
45 To start playback, a player first needs to read metadata. | |
46 This is done by sending a special request with the | |
271 | 47 <literal>start=0</literal> |
22 | 48 argument. Many encoding software will insert the metadata at |
49 the end of the file. This is bad for pseudo-streaming: | |
50 the metadata needs to be located at the beginning of the file, | |
51 or else the entire file will have to be downloaded before it | |
52 starts playing. If a file is well-formed (with metadata at the | |
53 beginning of a file), nginx just sends back the contents of a file. | |
54 Otherwise, it has to read the file and prepare a new stream so that | |
55 metadata comes before media data. | |
56 This involves some CPU, memory, and disk I/O overhead, | |
57 so it is a good idea to | |
52
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58 <link |
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59 url="http://flowplayer.org/plugins/streaming/pseudostreaming.html#prepare"> |
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60 prepare an original file for pseudo-streaming</link>, |
22 | 61 rather than having nginx do this on every such request. |
62 </para> | |
63 | |
64 <para> | |
65 For a matching request with a non-zero | |
271 | 66 <literal>start</literal> |
22 | 67 argument, nginx will read metadata from the file, prepare the |
68 stream starting from the requested offset, and send it to a client. | |
69 This has the same overhead as described above. | |
70 </para> | |
71 | |
72 <para> | |
73 If a matching request does not include the | |
271 | 74 <literal>start</literal> |
22 | 75 argument, there is no overhead, and the file is just sent as a static resource. |
76 Some players also support byte-range requests, and thus do not require | |
77 this module at all. | |
78 </para> | |
79 | |
80 <para> | |
81 This module is not built by default, it should be enabled with the | |
271 | 82 <literal>--with-http_mp4_module</literal> |
22 | 83 configuration parameter. |
84 <note> | |
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85 If a third-party mp4 module was previously used, it needs to be disabled. |
22 | 86 </note> |
87 </para> | |
88 | |
89 <para> | |
90 A similar pseudo-streaming support for FLV files is provided by the module | |
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91 <link doc="ngx_http_flv_module.xml">ngx_http_flv_module</link>. |
22 | 92 </para> |
93 | |
94 </section> | |
95 | |
96 | |
53
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97 <section id="example" name="Example Configuration"> |
22 | 98 |
99 <para> | |
100 <example> | |
101 location /video/ { | |
102 mp4; | |
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103 mp4_buffer_size 1m; |
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104 mp4_max_buffer_size 5m; |
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105 mp4_limit_rate on; |
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106 mp4_limit_rate_after 30s; |
22 | 107 } |
108 </example> | |
109 </para> | |
110 | |
111 </section> | |
112 | |
113 | |
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114 <section id="directives" name="Directives"> |
22 | 115 |
116 <directive name="mp4"> | |
102
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117 <syntax/> |
22 | 118 <default/> |
119 <context>location</context> | |
120 | |
121 <para> | |
122 Turns on module processing in a surrounding location. | |
123 </para> | |
124 | |
125 </directive> | |
126 | |
127 | |
128 <directive name="mp4_buffer_size"> | |
271 | 129 <syntax><value>size</value></syntax> |
102
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130 <default>512K</default> |
22 | 131 <context>http</context> |
132 <context>server</context> | |
133 <context>location</context> | |
134 | |
135 <para> | |
136 Sets the initial size of a memory buffer used to process MP4 files. | |
137 </para> | |
138 | |
139 </directive> | |
140 | |
141 | |
142 <directive name="mp4_max_buffer_size"> | |
271 | 143 <syntax><value>size</value></syntax> |
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144 <default>10M</default> |
22 | 145 <context>http</context> |
146 <context>server</context> | |
147 <context>location</context> | |
148 | |
149 <para> | |
150 During metadata processing, a larger buffer may become necessary. | |
271 | 151 Its size cannot exceed the specified <value>size</value>, |
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152 or else nginx will return the server error |
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153 <http-status code="500" text="Internal Server Error"/>, |
22 | 154 and log the following: |
155 <example> | |
156 "/some/movie/file.mp4" mp4 moov atom is too large: | |
157 12583268, you may want to increase mp4_max_buffer_size | |
158 </example> | |
159 </para> | |
160 | |
161 </directive> | |
162 | |
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163 |
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164 <directive name="mp4_limit_rate"> |
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165 <syntax> |
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166 <literal>on</literal> | |
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167 <literal>off</literal> | |
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168 <value>factor</value></syntax> |
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169 <default>off</default> |
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170 <context>http</context> |
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171 <context>server</context> |
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172 <context>location</context> |
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173 |
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174 <para> |
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175 Enables or disables rate limiting based on the average bitrate of the |
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176 MP4 file served. |
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177 To calculate the rate, the bitrate is multiplied by the specified |
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178 <value>factor</value>. |
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179 The special value “<literal>on</literal>” corresponds to the factor of 1.1. |
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180 </para> |
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181 |
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182 <para> |
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183 <note> |
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184 This directive is available as part of our <commercial_version/> only. |
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185 </note> |
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186 </para> |
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187 |
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188 </directive> |
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189 |
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190 |
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191 <directive name="mp4_limit_rate_after"> |
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192 <syntax><value>time</value></syntax> |
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193 <default>1m</default> |
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194 <context>http</context> |
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195 <context>server</context> |
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196 <context>location</context> |
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197 |
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198 <para> |
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199 Limits the rate after sending the specified amount of media data. |
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200 </para> |
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201 |
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202 <para> |
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203 <note> |
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204 This directive is available as part of our <commercial_version/> only. |
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205 </note> |
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206 </para> |
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207 |
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208 </directive> |
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209 |
22 | 210 </section> |
211 | |
212 </module> |