Mercurial > hg > nginx-site
annotate xml/en/docs/http/ngx_http_mp4_module.xml @ 589:764fbac1b8b4
Added document revision.
| author | Ruslan Ermilov <ru@nginx.com> |
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| date | Tue, 17 Jul 2012 05:02:15 +0000 |
| parents | be54c443235a |
| children | 77a3314c74a7 |
| 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" |
| 12 rev="1"> | |
| 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 |
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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 | |
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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> | |
| 85 If you were using the third-party mp4 module, be sure to disable it. | |
| 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 | |
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97 <section id="example" name="Example Configuration"> |
| 22 | 98 |
| 99 <para> | |
| 100 <example> | |
| 101 location /video/ { | |
| 102 mp4; | |
| 103 mp4_buffer_size 1m; | |
| 104 mp4_max_buffer_size 5m; | |
| 105 } | |
| 106 </example> | |
| 107 </para> | |
| 108 | |
| 109 </section> | |
| 110 | |
| 111 | |
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112 <section id="directives" name="Directives"> |
| 22 | 113 |
| 114 <directive name="mp4"> | |
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115 <syntax/> |
| 22 | 116 <default/> |
| 117 <context>location</context> | |
| 118 | |
| 119 <para> | |
| 120 Turns on module processing in a surrounding location. | |
| 121 </para> | |
| 122 | |
| 123 </directive> | |
| 124 | |
| 125 | |
| 126 <directive name="mp4_buffer_size"> | |
| 271 | 127 <syntax><value>size</value></syntax> |
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128 <default>512K</default> |
| 22 | 129 <context>http</context> |
| 130 <context>server</context> | |
| 131 <context>location</context> | |
| 132 | |
| 133 <para> | |
| 134 Sets the initial size of a memory buffer used to process MP4 files. | |
| 135 </para> | |
| 136 | |
| 137 </directive> | |
| 138 | |
| 139 | |
| 140 <directive name="mp4_max_buffer_size"> | |
| 271 | 141 <syntax><value>size</value></syntax> |
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142 <default>10M</default> |
| 22 | 143 <context>http</context> |
| 144 <context>server</context> | |
| 145 <context>location</context> | |
| 146 | |
| 147 <para> | |
| 148 During metadata processing, a larger buffer may become necessary. | |
| 271 | 149 Its size cannot exceed the specified <value>size</value>, |
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150 or else nginx will return the server error |
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151 <http-status code="500" text="Internal Server Error"/>, |
| 22 | 152 and log the following: |
| 153 <example> | |
| 154 "/some/movie/file.mp4" mp4 moov atom is too large: | |
| 155 12583268, you may want to increase mp4_max_buffer_size | |
| 156 </example> | |
| 157 </para> | |
| 158 | |
| 159 </directive> | |
| 160 | |
| 161 </section> | |
| 162 | |
| 163 </module> |