== link:index.html[Index] -> link:modules.html[Modules] -> link:modules_handlers.html[Handlers]

Handler: Audio/Video Streaming
------------------------------

This handler is used to stream media files. Both audio and video files
are supported.

The two main features of this module are:

  . `Automatic Traffic Shaping`: All the media files handled by this
    module will be analyzed, so it figures the media bitrate. Once the
    module knows it, it will limit the speed to that bitrate, so
    server bandwidth is not wasted in the case the client stops
    watching or listening to the file before it has finished. This
    feature also helps the server to handle a higher user concurrency
    before the bandwidth limit is reached.

  . `Seeking support`: There are some web media players that support
    media seeking by using a ?'start'= parameter. So far, this method
    is supported for FLV files, and it will be eventually supported
    for H264 videos as well.

If the 'Automatic Traffic Shaping' is enabled, all the media formats
will be streamed, independently on whether or not seeking is supported
for that format.  For instance, even though 'seeking' wouldn't work,
any MP3, OGG, AVI or Matroska file would be streamed according to
their bitrate.


Parameters: Listing
~~~~~~~~~~~~~~~~~~~
[cols="20%,10%,70%",options="header"]
|====================================================================
|Parameters       |Type    |Description
|`Auto Rate`      |boolean |Whether to enable the bitrate based
                            bandwidth limit.
|`Speedup Factor` |float   |Optional. It is the factor by which the
                            bandwidth limit would be multiplied.
                            Default: 0.1.
|`Initial Boost`  |number  |Optional. Seconds of media that should be
                            sent before setting the bandwidth limit.
                            This allows the client to buffer some
                            media. Default: 5 (seconds).
|====================================================================


Notes on FLV streaming
~~~~~~~~~~~~~~~~~~~~~~

It is important to remember that FLV videos must be indexed. It is
only possible to seek along the media file if it has some meta data
tags. Without these tags, seeking just would not work.

There are tools like link:http://inlet-media.de/flvtool2[FLVTool2],
link:http://www.buraks.com/flvmdi/[FLVMDI] or
link:http://yamdi.sourceforge.net/[Yamdi] that can be used to insert
these tags.

Notes on H264 (mp4) streaming
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

H264 files must be written in a special way so the server can stream
them. If a H264 file is ready for progressive streaming, Flash 9 (and
higher) will be able to play it while it's being downloaded.

From a technical point of view, the server needs the H264 file to have
its moov atoms (or boxes) in front of the data. The `qt-faststart.c`
program - shipped with FFMpeg - rewrites H264 files so their atoms are
placed in the required order.