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annotate xml/en/docs/http/ngx_http_mp4_module.xml @ 1096:f34be6b26447
Corrected text formatting for ngx_http_mp4_module.
| author | Yaroslav Zhuravlev <yar@nginx.com> |
|---|---|
| date | Tue, 04 Mar 2014 13:02:21 +0000 |
| parents | 379cb572a7ec |
| children | 1fcf8c840dbe |
| rev | line source |
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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> | |
| 966 | 17 The <literal>ngx_http_mp4_module</literal> module provides pseudo-streaming |
| 18 server-side support for H.264/AAC files. | |
| 19 Such files typically have the <path>.mp4</path>, <path>.m4v</path>, | |
| 20 or <path>.m4a</path> filename extensions. | |
| 22 | 21 </para> |
| 22 | |
| 23 <para> | |
| 966 | 24 The pseudo-streaming works in alliance with a compatible Flash players. |
| 22 | 25 A player sends an HTTP request to the server with a start time |
| 966 | 26 specified in the query string argument (named simply |
| 271 | 27 <literal>start</literal> |
| 966 | 28 and specified in seconds), and the server responds with the stream |
| 29 such that its start position corresponds to the requested time, | |
| 22 | 30 for example: |
| 31 <example> | |
| 32 http://example.com/elephants_dream.mp4?start=238.88 | |
| 33 </example> | |
| 966 | 34 This allows performing a random seeking at any time, or starting playback |
| 35 in the middle of the timeline. | |
| 22 | 36 </para> |
| 37 | |
| 38 <para> | |
| 39 To support seeking, H.264-based formats store the metadata | |
| 40 in the so-called “moov atom.” | |
| 41 It is a part of the file that holds the index information for the | |
| 42 whole file. | |
| 43 </para> | |
| 44 | |
| 45 <para> | |
| 46 To start playback, a player first needs to read metadata. | |
| 47 This is done by sending a special request with the | |
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48 <literal>start=0</literal> argument. |
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49 Much of encoding software will insert the metadata at |
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50 the end of the file. |
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51 This is bad for pseudo-streaming: |
| 966 | 52 the metadata should be located at the beginning of the file, |
| 53 or else the entire file will have to be downloaded to | |
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54 start playing. |
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55 If a file is well-formed (with metadata at the |
| 966 | 56 beginning of a file), nginx just sends back the file contents. |
| 22 | 57 Otherwise, it has to read the file and prepare a new stream so that |
| 966 | 58 the metadata comes before the media data. |
| 22 | 59 This involves some CPU, memory, and disk I/O overhead, |
| 60 so it is a good idea to | |
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61 <link |
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62 url="http://flowplayer.org/plugins/streaming/pseudostreaming.html#prepare"> |
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63 prepare an original file for pseudo-streaming</link>, |
| 22 | 64 rather than having nginx do this on every such request. |
| 65 </para> | |
| 66 | |
| 67 <para> | |
| 68 For a matching request with a non-zero | |
| 271 | 69 <literal>start</literal> |
| 966 | 70 argument, nginx will read the metadata from the file, prepare the |
| 22 | 71 stream starting from the requested offset, and send it to a client. |
| 72 This has the same overhead as described above. | |
| 73 </para> | |
| 74 | |
| 75 <para> | |
| 76 If a matching request does not include the | |
| 271 | 77 <literal>start</literal> |
| 22 | 78 argument, there is no overhead, and the file is just sent as a static resource. |
| 79 Some players also support byte-range requests, and thus do not require | |
| 80 this module at all. | |
| 81 </para> | |
| 82 | |
| 83 <para> | |
| 84 This module is not built by default, it should be enabled with the | |
| 271 | 85 <literal>--with-http_mp4_module</literal> |
| 22 | 86 configuration parameter. |
| 87 <note> | |
| 966 | 88 If a third-party mp4 module was previously used, it should be disabled. |
| 22 | 89 </note> |
| 90 </para> | |
| 91 | |
| 92 <para> | |
| 966 | 93 A similar pseudo-streaming support for FLV files is provided by the |
| 94 <link doc="ngx_http_flv_module.xml">ngx_http_flv_module</link> module. | |
| 22 | 95 </para> |
| 96 | |
| 97 </section> | |
| 98 | |
| 99 | |
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100 <section id="example" name="Example Configuration"> |
| 22 | 101 |
| 102 <para> | |
| 103 <example> | |
| 104 location /video/ { | |
| 105 mp4; | |
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106 mp4_buffer_size 1m; |
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107 mp4_max_buffer_size 5m; |
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108 mp4_limit_rate on; |
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109 mp4_limit_rate_after 30s; |
| 22 | 110 } |
| 111 </example> | |
| 112 </para> | |
| 113 | |
| 114 </section> | |
| 115 | |
| 116 | |
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117 <section id="directives" name="Directives"> |
| 22 | 118 |
| 119 <directive name="mp4"> | |
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120 <syntax/> |
| 22 | 121 <default/> |
| 122 <context>location</context> | |
| 123 | |
| 124 <para> | |
| 125 Turns on module processing in a surrounding location. | |
| 126 </para> | |
| 127 | |
| 128 </directive> | |
| 129 | |
| 130 | |
| 131 <directive name="mp4_buffer_size"> | |
| 271 | 132 <syntax><value>size</value></syntax> |
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133 <default>512K</default> |
| 22 | 134 <context>http</context> |
| 135 <context>server</context> | |
| 136 <context>location</context> | |
| 137 | |
| 138 <para> | |
| 966 | 139 Sets the initial size of a memory buffer used for processing MP4 files. |
| 22 | 140 </para> |
| 141 | |
| 142 </directive> | |
| 143 | |
| 144 | |
| 145 <directive name="mp4_max_buffer_size"> | |
| 271 | 146 <syntax><value>size</value></syntax> |
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147 <default>10M</default> |
| 22 | 148 <context>http</context> |
| 149 <context>server</context> | |
| 150 <context>location</context> | |
| 151 | |
| 152 <para> | |
| 153 During metadata processing, a larger buffer may become necessary. | |
| 271 | 154 Its size cannot exceed the specified <value>size</value>, |
| 966 | 155 or else nginx will return the |
| 156 <http-status code="500" text="Internal Server Error"/> server error, | |
| 157 and log the following message: | |
| 22 | 158 <example> |
| 159 "/some/movie/file.mp4" mp4 moov atom is too large: | |
| 160 12583268, you may want to increase mp4_max_buffer_size | |
| 161 </example> | |
| 162 </para> | |
| 163 | |
| 164 </directive> | |
| 165 | |
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166 |
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167 <directive name="mp4_limit_rate"> |
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168 <syntax> |
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169 <literal>on</literal> | |
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170 <literal>off</literal> | |
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171 <value>factor</value></syntax> |
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172 <default>off</default> |
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173 <context>http</context> |
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174 <context>server</context> |
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175 <context>location</context> |
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176 |
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177 <para> |
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178 Enables or disables rate limiting based on the average bitrate of the |
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179 MP4 file served. |
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180 To calculate the rate, the bitrate is multiplied by the specified |
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181 <value>factor</value>. |
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182 The special value “<literal>on</literal>” corresponds to the factor of 1.1. |
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183 </para> |
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184 |
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185 <para> |
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186 <note> |
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187 This directive is available as part of our <commercial_version/>. |
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188 </note> |
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189 </para> |
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190 |
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191 </directive> |
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192 |
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193 |
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194 <directive name="mp4_limit_rate_after"> |
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195 <syntax><value>time</value></syntax> |
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196 <default>1m</default> |
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197 <context>http</context> |
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198 <context>server</context> |
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199 <context>location</context> |
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200 |
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201 <para> |
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202 Limits the rate after sending the specified amount of media data. |
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203 </para> |
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204 |
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205 <para> |
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206 <note> |
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207 This directive is available as part of our <commercial_version/>. |
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208 </note> |
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209 </para> |
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210 |
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211 </directive> |
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212 |
| 22 | 213 </section> |
| 214 | |
| 215 </module> |