NGINX-based VOD Packager

nginx-vod-module

Features

• On-the-fly repackaging of MP4 files to DASH, HDS, HLS, MSS

• Working modes:

  1. Local - serve locally accessible files (local disk/NFS mounted)
  2. Remote - serve files accessible via HTTP using range requests
  3. Mapped - serve files according to a specification encoded in JSON format. The JSON can pulled from a remote server, or read from a local file

• Adaptive bitrate support

• Playlist support (playing several different media files one after the other) - mapped mode only

• Simulated live support (generating a live stream from MP4 files) - mapped mode only

• Fallback support for file not found in local/mapped modes (useful in multi-datacenter environments)

• Video codecs: H264, H265 (DASH/HLS)

• Audio codecs: AAC

• Audio only/video only files

• Track selection for multi audio/video MP4 files

• Playback rate change - 0.5x up to 2x (requires libavcodec and libavfilter)

• Source file clipping (only from I-Frame to P-frame)

• Support for variable segment lengths - enabling the player to select the optimal bitrate fast, without the overhead of short segments for the whole duration of the video

• Clipping of MP4 files for progressive download playback

• Decryption of CENC-encrypted MP4 files (it is possible to create such files with MP4Box)

• DASH: common encryption (CENC) support

• MSS: PlayReady encryption support

• HLS: Mux audio and video streams from separate MP4 files (HLS/HDS)

• HLS: Generation of I-frames playlist (EXT-X-I-FRAMES-ONLY)

• HLS: support for AES-128 / SAMPLE-AES encryption

Limitations

• Only AAC audio is supported (MP3 audio is not)

• Track selection and playback rate change are not supported in progressive download

• I-frames playlist generation is not supported when encryption is enabled

• Tested on Linux only

Installation

Build

cd to NGINX source directory and execute:

./configure --add-module=/path/to/nginx-vod-module
make
make install

For asynchronous I/O support add --with-file-aio (highly recommended, local and mapped modes only)

./configure --add-module=/path/to/nginx-vod-module --with-file-aio

For asynchronous file open using thread pool add --with-threads (nginx 1.7.11+, local and mapped modes only)

./configure --add-module=/path/to/nginx-vod-module --with-threads

We recommend setting the gcc optimization parameter -O3 - we got about 8% reduction in the mp4 parse time and frame processing time compared to the nginx default -O

./configure --add-module=/path/to/nginx-vod-module --with-cc-opt="-O3"

To compile nginx with debug messages add --with-debug

./configure --add-module=/path/to/nginx-vod-module --with-debug

To disable compiler optimizations (for debugging with gdb) add --with-cc-opt="-O0"

./configure --add-module=/path/to/nginx-vod-module --with-cc-opt="-O0"

RHEL/CentOS RPM

If you are using RHEL or CentOS 6, you can install by setting up the repo:

# rpm -ihv http://installrepo.kaltura.org/releases/kaltura-release.noarch.rpm
# yum install kaltura-nginx

If you are using RHEL/CentOS7, install the kaltura-release RPM and modify /etc/yum.repos.d/kaltura.repo to read:

baseurl = http://installrepo.kaltura.org/releases/rhel7/RPMS/$basearch/

Instead of the default:

baseurl = http://installrepo.kaltura.org/releases/latest/RPMS/$basearch/

Debian/Ubuntu deb package

# wget -O - http://installrepo.kaltura.org/repo/apt/debian/kaltura-deb.gpg.key|apt-key add -
# echo "deb [arch=amd64] http://installrepo.kaltura.org/repo/apt/debian kajam main" > /etc/apt/sources.list.d/kaltura.list
# apt-get update
# apt-get install kaltura-nginx

Ubuntu NOTE: You must also make sure the multiverse repo is enabled in /etc/apt/sources.list

URL structure

Basic URL structure

The basic structure of an nginx-vod-module URL is: http://<domain>/<location>/<fileuri>/<filename>

Where:

• domain - the domain of the nginx-vod-module server
• location - the location specified in the nginx conf
• fileuri - a URI to the mp4 file:
  • local mode - the full file path is determined according to the root / alias nginx.conf directives
  • mapped mode - the full file path is determined according to the JSON received from the upstream / local file
  • remote mode - the mp4 file is read from upstream in chunks
  • Note: in mapped & remote modes, the URL of the upstream request is http://<upstream>/<location>/<fileuri>?<extraargs> (extraargs is determined by the vod_upstream_extra_args parameter)
• filename - detailed below

Multi URL structure

Multi URLs are used to encode several URLs on a single URL. A multi URL can be used to specify the URLs of several different MP4 files that should be included together in a DASH MPD for example.

The structure of a multi URL is: http://<domain>/<location>/<prefix>,<middle1>,<middle2>,<middle3>,<postfix>.urlset/<filename>

The sample URL above represents 3 URLs:

• http://<domain>/<location>/<prefix><middle1><postfix>/<filename>
• http://<domain>/<location>/<prefix><middle2><postfix>/<filename>
• http://<domain>/<location>/<prefix><middle3><postfix>/<filename>

The suffix .urlset (can be changed with vod_multi_uri_suffix) indicates that the URL should be treated as a multi URL.

URL path parameters

The following parameters are supported on the URL path:

• clipFrom - an offset in milliseconds since the beginning of the video, where the generated stream should start. For example, .../clipFrom/10000/... will generate a stream that starts 10 seconds into the video.
• clipTo - an offset in milliseconds since the beginning of the video, where the generated stream should end. For example, .../clipTo/60000/... will generate a stream truncated to 60 seconds.
• tracks - can be used to select specific audio/video tracks. The structure of parameter is: v<id1>-v<id2>-a<id1>-a<id2>... For example, .../tracks/v1-a1/... will select the first video track and first audio track. The default is to include all tracks.

Filename structure

The structure of filename is: <basename>[<fileparams>][<trackparams>].<extension>

Where:

• basename + extension - the set of options is packager specific (the list below applies to the default settings):
  • dash - manifest.mpd
  • hds - manifest.f4m
  • hls master playlist - master.m3u8
  • hls media playlist - index.m3u8
  • mss - manifest
• fileparams - can be used to select specific files (URLs) when using multi URLs. For example, manifest-f1.mpd will return an MPD only from the first URL.
• trackparams - can be used to select specific audio/video tracks. For example, manifest-a1.f4m will return an F4M containing only the first audio stream. The default is to include the first audio and first video tracks of each file. The tracks selected on the file name are AND-ed with the tracks selected with the /tracks/ path parameter.

Mapping response format

When configured to run in mapped mode, nginx-vod-module issues an HTTP request to a configured upstream server in order to receive the layout of media streams it should generate. The response has to be in JSON format.

This section contains a few simple examples followed by a reference of the supported objects and fields. But first, a couple of definitions:

1. Source Clip - a set of audio and/or video frames (tracks) extracted from a single media file
2. Filter - a manipulation that can be applied on audio/video frames. The following filters are supported:

• rate (speed) change - applies to both audio and video
• audio volume change
• mix - can be used to merge several audio tracks together, or to merge the audio of source A with the video of source B

2. Clip - the result of applying zero or more filters on a set of source clips
3. Sequence - a set of clips that should be played one after the other.
4. Set - several sequences that play together as an adaptive set, each sequence must have the same number of clips.

Simple mapping

The JSON below maps the request URI to a single MP4 file:

{
	"sequences": [
		{
			"clips": [
				{
					"type": "source",
					"path": "/path/to/video.mp4"
				}
			]
		}
	]
}

When using multi URLs, this is the only allowed JSON pattern. In other words, it is not possible to combine more complex JSONs using multi URL.

Adaptive set

As an alternative to using multi URL, an adaptive set can be defined via JSON:

{
	"sequences": [
		{
			"clips": [
				{
					"type": "source",
					"path": "/path/to/bitrate1.mp4"
				}
			]
		},
		{
			"clips": [
				{
					"type": "source",
					"path": "/path/to/bitrate2.mp4"
				}
			]
		}
	]
}

Playlist

The JSON below will play 35 seconds of video1 followed by 22 seconds of video2:

{
	"durations": [ 35000, 22000 ],
	"sequences": [
		{
			"clips": [
				{
					"type": "source",
					"path": "/path/to/video1.mp4"
				},
				{
					"type": "source",
					"path": "/path/to/video2.mp4"
				}
			]
		}
	]
}

Filters

The JSON below takes video1, plays it at x1.5 and mixes the audio of the result with the audio of video2, after reducing it to 50% volume:

{
	"sequences": [
		{
			"clips": [
				{
					"type": "mixFilter",
					"sources": [
						{
							"type": "rateFilter",
							"rate": 1.5,
							"source": {
								"type": "source",
								"path": "/path/to/video1.mp4"
							}
						},
						{
							"type": "gainFilter",
							"gain": 0.5,
							"source": {
								"type": "source",
								"path": "/path/to/video2.mp4",
								"tracks": "a1"
							}
						}
					]
				}
			]
		}
	]
}

Continuous live

The JSON below is a sample of a continuous live stream (=a live stream in which all videos have exactly the same encoding parameters). In practice, this JSON will have to be generated by some script, since it is time dependent. (see test/playlist.php for a sample implementation)

{
	"playlistType": "live",
	"discontinuity": false,
	"segmentBaseTime": 1451904060000,
	"firstClipTime": 1451917506000,
	"durations": [83000, 83000],
	"sequences": [
		{
			"clips": [
				{
					"type": "source",
					"path": "/path/to/video1.mp4"
				},
				{
					"type": "source",
					"path": "/path/to/video2.mp4"
				}
			]
		}
	]
}

Non-continuous live

The JSON below is a sample of a non-continuous live stream (=a live stream in which the videos have different encoding parameters). In practice, this JSON will have to be generated by some script, since it is time dependent (see test/playlist.php for a sample implementation)

{
	"playlistType": "live",
	"discontinuity": true,
	"initialClipIndex": 171,
	"initialSegmentIndex": 153,
	"firstClipTime": 1451918170000,
	"durations": [83000, 83000],
	"sequences": [
		{
			"clips": [
				{
					"type": "source",
					"path": "/path/to/video1.mp4"
				},
				{
					"type": "source",
					"path": "/path/to/video2.mp4"
				}
			]
		}
	]
}

Mapping reference

Set (top level object in the mapping JSON)

Mandatory fields:

• sequences - array of Sequence objects. The mapping has to contain at least one sequence and up to 32 sequences.

Optional fields:

• playlistType - string, can be set to live or vod, default is vod.
• durations - an array of integers representing clip durations in milliseconds. This field is mandatory if the mapping contains more than a single clip per sequence. If specified, this array must contain at least one element and up to 128 elements.
• discontinuity - boolean, indicates whether the different clips in each sequence have different media parameters. This field has different manifestations according to the delivery protocol - a value of true will generate #EXT-X-DISCONTINUITY in HLS, and a multi period MPD in DASH. The default value is true, set to false only if the media files were transcoded with exactly the same parameters (in AVC for example, the clips should have exactly the same SPS/PPS).
• consistentSequenceMediaInfo - boolean, currently affects only DASH. When set to true (default) the MPD will report the same media parameters in each period element. Setting to false can have severe performance implications for long sequences (nginx-vod-module has to read the media info of all clips included in the mapping in order to generate the MPD)

Live fields:

• firstClipTime - integer, mandatory for all live playlists, contains the absolute time of the first clip in the playlist, in milliseconds since the epoch (unixtime x 1000)
• segmentBaseTime - integer, mandatory for continuous live streams, contains the absolute time of the first segment of the stream, in milliseconds since the epoch (unixtime x 1000) This value must not change during playback.
• initialClipIndex - integer, mandatory for non-continuous live streams, contains the index of the first clip in the playlist. Whenever a clip is pushed out of the head of the playlist, this value must be incremented by one.
• initialSegmentIndex - integer, mandatory for non-continuous live streams, contains the index of the first segment in the playlist. Whenever a clip is pushed out of the head of the playlist, this value must be incremented by the number of segments in the clip.

Sequence

Mandatory fields:

• clips - array of Clip objects (mandatory). The number of elements must match the number the durations array specified on the set. If the durations array is not specified, the clips array must contain a single element.

Clip (abstract)

Mandatory fields:

• type - a string that defines the type of the clip. Allowed values are:
  • source
  • rateFilter
  • mixFilter
  • gainFilter
  • concat

Source clip

Mandatory fields:

• type - a string with the value source
• path - a string containing the path of the MP4 file

Optional fields:

• tracks - a string that specifies the tracks that should be used, the default is "v1-a1", which means the first video track and the first audio track
• clipFrom - an integer that specifies an offset in milliseconds, from the beginning of the media file, from which to start loading frames
• encryptionKey - a base64 encoded string containing the key (128 bit) that should be used to decrypt the media file.

Rate filter clip

Mandatory fields:

• type - a string with the value rateFilter
• rate - a float that specified the acceleration factor, e.g. a value of 2 means double speed. Allowed values are in the range 0.5 - 2 with up to two decimal points
• source - a clip object on which to perform the rate filtering

Gain filter clip

Mandatory fields:

• type - a string with the value gainFilter
• gain - a float that specified the amplification factor, e.g. a value of 2 means twice as loud. The gain must be positive with up to two decimal points
• source - a clip object on which to perform the gain filtering

Mix filter clip

Mandatory fields:

• type - a string with the value mixFilter
• sources - an array of Clip objects to mix. This array must contain at least one clip and up to 32 clips.

Concat filter clip

Mandatory fields:

• type - a string with the value concat
• paths - an array of strings, containings the paths of the MP4 files
• durations - an array of integers representing MP4 durations in milliseconds, this array must match the paths array in count and order.

Optional fields:

• tracks - a string that specifies the tracks that should be used, the default is "v1-a1", which means the first video track and the first audio track
• offset - an integer in milliseconds that indicates the timestamp offset of the first frame in the concatenated stream relative to the clip start time
• basePath - a string that should be added as a prefix to all the paths

Security

Authorization

CDN-based delivery

Media packaged by nginx-vod-module can be protected using CDN tokens, this works as follows:

• Some application authenticates the user and decides whether the user should be allowed to watch a specific video. If the user is allowed, the application generates a tokenized URL for the manifest of the video.
• The CDN validates the token, and if found to be valid, forwards the request to nginx-vod-module on the origin.
• The nginx server builds the manifest response and generates tokens for the segment URLs contained inside it. The module https://github.com/kaltura/nginx-secure-token-module can be used to accomplish this task, it currently support Akamai tokens and CloudFront tokens. See the readme of this module for more details.
• The CDN validates the token on each segment that is requested.

In this setup it also highly recommended to block direct access to the origin server by authenticating the CDN requests. Without this protection, a user who somehow gets the address of the origin will be able to bypass the CDN token enforcement. If using Akamai, this can be accomplished using https://github.com/refractalize/nginx_mod_akamai_g2o. For other CDNs, it may be possible to configure the CDN to send a secret header to the origin and then simply enforce the header using an nginx if statement:

		if ($http_x_secret_origin_header != "secret value") {
			return 403;
		}

In addition to the above, most CDNs support other access control settings, such as geo-location. These restrictions are completely transparent to the origin and should work well.

Direct delivery

Deployments in which the media is pulled directly from nginx-vod-module can protect the media using nginx access control directives, such allow, deny, or access_by_lua (for more complex scenarios).

In addition, it is possible to build a token based solution (as detailed in the previous section) without a CDN, by having the nginx server validate the token. The module https://github.com/kaltura/nginx-akamai-token-validate-module can be used to validate Akamai tokens. Locations on which the module is enabled will return 403 unless the request contains a valid Akamai token. See the readme of this module for more details.

URL encryption

As an alternative to tokenization, URL encryption can be used to prevent an attacker from being able to craft a playable URL. URL encryption can be implemented with https://github.com/kaltura/nginx-secure-token-module, and is supported for HLS and DASH (with manifest format set to segmentlist).

In terms of security, the main advantage of CDN tokens over URL encryption is that CDN tokens usually expire, while encrypted URLs do not (someone who obtains a playable URL will be able to use it indefinitely)

Media encryption

Nginx-vod-module supports AES-128 and SAMPLE-AES HLS encryption schemes. The main difference between media encryption and DRM (detailed below) is the mechanism used to transfer the encryption key to the client. With media encryption the key is fetched by the client by performing a simple GET request to nginx-vod-module, while with DRM the key is returned inside a vendor specific license response.

Media encryption reduces the problem of securing the media to the need to secure the encryption key. The media segment URLs (which compose the vast majority of the traffic) can be completely unprotected, and easily cacheable by any proxies between the client and servers (unlike tokenization). The encryption key request can then be protected using one of the methods mentioned above (CDN tokens, nginx access rules etc.).

In addition, it is possible to configure nginx-vod-module to return the encryption key over HTTPS while having the segments delivered over HTTP. The way to configure this is to set vod_segments_base_url to http://nginx-vod-host and set vod_https_header_name to host.

DRM

Nginx-vod-module has the ability to perform on-the-fly encryption for MPEG DASH (CENC), MSS Play Ready and FairPlay HLS. As in the case of media encryption, the encryption is performed while serving a video/audio segment to the client, therefore, when working with DRM it is recommended not to serve the content directly from nginx-vod-module to end-users. A more scalable architecture would be to use proxy servers or a CDN in order to cache the encrypted segments.

In order to perform the encryption, nginx-vod-module needs several parameters, including key & key_id, these parameters are fetched from an external server via HTTP GET requests. The vod_drm_upstream_location parameter specifies an nginx location that is used to access the DRM server, and the request uri is configured using vod_drm_request_uri (this parameter can include nginx variables). The response of the DRM server is a JSON, with the following format:

[{
	"pssh": [{
			"data": "CAESEGMyZjg2MTczN2NjNGYzODIaB2thbHR1cmEiCjBfbmptaWlwbXAqBVNEX0hE", 
			"uuid": "edef8ba9-79d6-4ace-a3c8-27dcd51d21ed"
		}], 
	"key": "GzoNU9Dfwc//Iq3/zbzMUw==", 
	"key_id": "YzJmODYxNzM3Y2M0ZjM4Mg=="
}]

• pssh.data - base64 encoded binary data, the format of this data is drm vendor specific
• pssh.uuid - the drm system UUID, in this case, edef8ba9-79d6-4ace-a3c8-27dcd51d21ed stands for Widevine
• key - base64 encoded encryption key (128 bit)
• key_id - base64 encoded key identifier (128 bit)
• iv - optional base64 encoded initialization vector (128 bit). The IV is currently used only in HLS (FairPlay), in the other protocols an IV is generated automatically by nginx-vod-module.

Sample configuration

Below is a sample configuration for Apple FairPlay HLS:

location ~ ^/fpshls/p/\d+/(sp/\d+/)?serveFlavor/entryId/([^/]+)/(.*) {
	vod hls;
	vod_hls_encryption_method sample-aes;
	vod_hls_encryption_key_uri "skd://entry-$2";
	vod_hls_encryption_key_format "com.apple.streamingkeydelivery";
	vod_hls_encryption_key_format_versions "1";

	vod_drm_enabled on;
	vod_drm_request_uri "/udrm/system/ovp/$vod_suburi";

	vod_last_modified_types *;
	add_header Access-Control-Allow-Headers '*';
	add_header Access-Control-Expose-Headers 'Server,range,Content-Length,Content-Range';
	add_header Access-Control-Allow-Methods 'GET, HEAD, OPTIONS';
	add_header Access-Control-Allow-Origin '*';
	expires 100d;
}

Performance recommendations

1. For medium/large scale deployments, don't have users play the videos directly from nginx-vod-module. Since all the different streaming protocols supported by nginx vod are HTTP based, they can be cached by standard HTTP proxies / CDNs. For medium scale add a layer of caching proxies between the vod module and the end users (can use standard nginx servers with proxy_pass & proxy_cache). For large scale deployments, it is recommended to use a CDN (such as Akamai, Level3 etc.).

   In general, it's best to have nginx vod as close as possible to where the mp4 files are stored, and have the caching proxies as close as possible to the end users.

2. Enable nginx-vod-module caches:

   • vod_metadata_cache - saves the need to re-read the video metadata for each segment. This cache should be rather large, in the order of GBs.
   • vod_response_cache - saves the responses of manifest requests. This cache may not be required when using a second layer of caching servers before nginx vod. No need to allocate a large buffer for this cache, 128M is probably more than enough for most deployments.
   • vod_path_mapping_cache - for mapped mode only, few MBs is usually enough.
   • nginx's open_file_cache - caches open file handles.

   The hit/miss ratios of these caches can be tracked by enabling performance counters (vod_performance_counters) and setting up a status page for nginx vod (vod_status)

3. In local & mapped modes, enable aio. - nginx has to be compiled with aio support, and it has to be enabled in nginx conf (aio on). You can verify it works by looking at the performance counters on the vod status page - read_file (aio off) vs. async_read_file (aio on)

4. In local & mapped modes, enable asynchronous file open - nginx has to be compiled with threads support, and vod_open_file_thread_pool has to be specified in nginx.conf. You can verify it works by looking at the performance counters on the vod status page - open_file vs. async_open_file

5. The muxing overhead of the streams generated by this module can be reduced by changing the following parameters:

   • HDS - set vod_hds_generate_moof_atom to off
   • HLS - set vod_hls_align_frames to off and vod_hls_interleave_frames to on

6. Enable gzip compression on manifest responses -

   gzip_types application/vnd.apple.mpegurl video/f4m application/dash+xml text/xml

7. Apply common nginx performance best practices, such as tcp_nodelay=on, client_header_timeout etc.

Common configuration directives

vod

• syntax: vod segmenter
• default: n/a
• context: location

Enables the nginx-vod module on the enclosing location. Currently the allowed values for segmenter are:

1. none - serves the MP4 files as is
2. dash - Dynamic Adaptive Streaming over HTTP packetizer
3. hds - Adobe HTTP Dynamic Streaming packetizer
4. hls - Apple HTTP Live Streaming packetizer
5. mss - Microsoft Smooth Streaming packetizer

vod_mode

• syntax: vod_mode mode
• default: local
• context: http, server, location

Sets the file access mode - local, remote or mapped (see the features section above for more details)

vod_status

• syntax: vod_status
• default: n/a
• context: location

Enables the nginx-vod status page on the enclosing location.

vod_multi_uri_suffix

• syntax: vod_multi_uri_suffix suffix
• default: .urlset
• context: http, server, location

A URL suffix that is used to identify multi URLs. A multi URL is a way to encode several different URLs that should be played together as an adaptive streaming set, under a single URL. When the default suffix is used, an HLS set URL may look like: http://host/hls/common-prefix,bitrate1,bitrate2,common-suffix.urlset/master.m3u8

vod_segment_duration

• syntax: vod_segment_duration duration
• default: 10s
• context: http, server, location

Sets the segment duration in milliseconds.

vod_live_segment_count

• syntax: vod_live_segment_count count
• default: 3
• context: http, server, location

Sets the number of segments that should be returned in a live manifest.

vod_bootstrap_segment_durations

• syntax: vod_bootstrap_segment_durations duration
• default: none
• context: http, server, location

Adds a bootstrap segment duration in milliseconds. This setting can be used to make the first few segments shorter than the default segment duration, thus making the adaptive flavor selection kick-in earlier without the overhead of short segments throughout the video.

vod_align_segments_to_key_frames

• syntax: vod_align_segments_to_key_frames on/off
• default: off
• context: http, server, location

When enabled, the module forces all segments to start with a key frame. Enabling this setting can lead to differences between the actual segment durations and the durations reported in the manifest (unless vod_manifest_segment_durations_mode is set to accurate).

vod_segment_count_policy

• syntax: vod_segment_count_policy last_short/last_long/last_rounded
• default: last_short
• context: http, server, location

Configures the policy for calculating the segment count, for segment_duration = 10 seconds:

• last_short - a file of 33 sec is partitioned as - 10, 10, 10, 3
• last_long - a file of 33 sec is partitioned as - 10, 10, 13
• last_rounded - a file of 33 sec is partitioned as - 10, 10, 13, a file of 38 sec is partitioned as 10, 10, 10, 8

vod_manifest_segment_durations_mode

• syntax: vod_manifest_segment_durations_mode estimate/accurate
• default: estimate
• context: http, server, location

Configures the calculation mode of segment durations within manifest requests:

• estimate - reports the duration as configured in nginx.conf, e.g. if vod_segment_duration has the value 10000, an HLS manifest will contain #EXTINF:10
• accurate - reports the exact duration of the segment, taking into account the frame durations, e.g. for a frame rate of 29.97 and 10 second segments it will report the first segment as 10.01. accurate mode also takes into account the key frame alignment, in case vod_align_segments_to_key_frames is on

vod_secret_key

• syntax: vod_secret_key string
• default: empty
• context: http, server, location

Sets the seed that is used to generate the TS encryption key and DASH/MSS encryption IVs. The parameter value can contain variables, and will usually have the structure "secret-$vod_filepath". See the list of nginx variables added by this module below.

vod_duplicate_bitrate_threshold

• syntax: vod_duplicate_bitrate_threshold threshold
• default: 4096
• context: http, server, location

The bitrate threshold for removing identical bitrates, streams whose bitrate differences are less than this value will be considered identical.

vod_https_header_name

• syntax: vod_https_header_name name
• default: empty
• context: http, server, location

Sets the name of an HTTP header whose existence determines whether the request was issued over HTTPS. If not set, the decision is made according to the protocol used to connect to the nginx server. A common scenario for using this setting is a load-balancer placed before the nginx that performs SSL-offloading.

vod_segments_base_url

• syntax: vod_segments_base_url url
• default: empty
• context: http, server, location

Sets the base URL (usually domain only) that should be used for delivering video segments. When empty, the host header sent on the request will be used as the domain. The scheme (http/https) used in the returned URLs is determined by:

• the value of vod_segments_base_url, if it starts with http:// or https://
• the existence of a request header whose name matches the value of vod_https_header_name, if vod_https_header_name is not empty
• the type of connection used to connect to the nginx server The setting currently affects only HLS.

vod_open_file_thread_pool

• syntax: vod_open_file_thread_pool pool_name
• default: off
• context: http, server, location

Enables the use of asynchronous file open via thread pool. The thread pool must be defined with a thread_pool directive, if no pool name is specified the default pool is used. This directive is supported only on nginx 1.7.11 or newer when compiling with --add-threads. Note: this directive currently disables the use of nginx's open_file_cache by nginx-vod-module

vod_metadata_cache

• syntax: vod_metadata_cache zone_name zone_size [expiration]
• default: off
• context: http, server, location

Configures the size and shared memory object name of the video metadata cache. For MP4 files, this cache holds the moov atom.

vod_response_cache

• syntax: vod_response_cache zone_name zone_size [expiration]
• default: off
• context: http, server, location

Configures the size and shared memory object name of the response cache. The response cache holds manifests and other non-video content (like DASH init segment, HLS encryption key etc.). Video segments are not cached.

vod_live_response_cache

• syntax: vod_live_response_cache zone_name zone_size [expiration]
• default: off
• context: http, server, location

Configures the size and shared memory object name of the response cache for time changing live responses. This cache holds the following types of responses for live: DASH MPD, HLS index M3U8, HDS bootstrap, MSS manifest.

vod_initial_read_size

• syntax: vod_initial_read_size size
• default: 4K
• context: http, server, location

Sets the size of the initial read operation of the MP4 file.

vod_max_metadata_size

• syntax: vod_max_metadata_size size
• default: 128MB
• context: http, server, location

Sets the maximum supported video metadata size (for MP4 - moov atom size)

vod_max_frames_size

• syntax: vod_max_frames_size size
• default: 16MB
• context: http, server, location

Sets the limit on the total size of the frames of a single segment

vod_cache_buffer_size

• syntax: vod_cache_buffer_size size
• default: 256K
• context: http, server, location

Sets the size of the cache buffers used when reading MP4 frames.

vod_ignore_edit_list

• syntax: vod_ignore_edit_list on/off
• default: off
• context: http, server, location

When enabled, the module ignores any edit lists (elst) in the MP4 file.

vod_upstream_location

• syntax: vod_upstream_location location
• default: none
• context: http, server, location

Sets an nginx location that is used to read the MP4 file (remote mode) or mapping the request URI (mapped mode).

vod_max_upstream_headers_size

• syntax: vod_max_upstream_headers_size size
• default: 4k
• context: http, server, location

Sets the size that is allocated for holding the response headers when issuing upstream requests (to vod_xxx_upstream_location).

vod_upstream_extra_args

• syntax: vod_upstream_extra_args "arg1=value1&arg2=value2&..."
• default: empty
• context: http, server, location

Extra query string arguments that should be added to the upstream request (remote/mapped modes only). The parameter value can contain variables.

vod_path_mapping_cache

• syntax: vod_path_mapping_cache zone_name zone_size [expiration]
• default: off
• context: http, server, location

Configures the size and shared memory object name of the path mapping cache for vod (mapped mode only).

vod_live_path_mapping_cache

• syntax: vod_live_path_mapping_cache zone_name zone_size [expiration]
• default: off
• context: http, server, location

Configures the size and shared memory object name of the path mapping cache for live (mapped mode only).

vod_path_response_prefix

• syntax: vod_path_response_prefix prefix
• default: {"sequences":[{"clips":[{"type":"source","path":"
• context: http, server, location

Sets the prefix that is expected in URI mapping responses (mapped mode only).

vod_path_response_postfix

• syntax: vod_path_response_postfix postfix
• default: "}]}]}
• context: http, server, location

Sets the postfix that is expected in URI mapping responses (mapped mode only).

vod_max_mapping_response_size

• syntax: vod_max_mapping_response_size length
• default: 1K
• context: http, server, location

Sets the maximum length of a path returned from upstream (mapped mode only).

vod_fallback_upstream_location

• syntax: vod_fallback_upstream_location location
• default: none
• context: http, server, location

Sets an nginx location to which the request is forwarded after encountering a file not found error (local/mapped modes only).

vod_proxy_header_name

• syntax: vod_proxy_header_name name
• default: X-Kaltura-Proxy
• context: http, server, location

Sets the name of an HTTP header that is used to prevent fallback proxy loops (local/mapped modes only).

vod_proxy_header_value

• syntax: vod_proxy_header_value name
• default: dumpApiRequest
• context: http, server, location

Sets the value of an HTTP header that is used to prevent fallback proxy loops (local/mapped modes only).

vod_clip_to_param_name

• syntax: vod_clip_to_param_name name
• default: clipTo
• context: http, server, location

The name of the clip to request parameter.

vod_clip_from_param_name

• syntax: vod_clip_from_param_name name
• default: clipFrom
• context: http, server, location

The name of the clip from request parameter.

vod_tracks_param_name

• syntax: vod_tracks_param_name name
• default: tracks
• context: http, server, location

The name of the tracks request parameter.

vod_speed_param_name

• syntax: vod_speed_param_name name
• default: tracks
• context: http, server, location

The name of the speed request parameter.

vod_performance_counters

• syntax: vod_performance_counters zone_name
• default: off
• context: http, server, location

Configures the shared memory object name of the performance counters

vod_expires

• syntax: vod_expires time
• default: none
• context: http, server, location

Sets the value of the "Expires" and "Cache-Control" response headers for successful requests. This directive is similar to nginx's built-in expires directive, except that it only supports the expiration interval scenario (epoch, max, off, day time are not supported) Main motivation for using this directive instead of the built-in expires is to have different expiration for VOD and dynamic live content. If this directive is not specified, nginx-vod-module will not set the "Expires" / "Cache-Control" headers.

vod_expires_live

• syntax: vod_expires_live time
• default: none
• context: http, server, location

Same as vod_expires (above) for dynamic live content. In DASH, for example, the expiration of the video fragments is determined by vod_expires, while vod_expires_live determines the expiration of the MPD.

vod_last_modified

• syntax: vod_last_modified time
• default: none
• context: http, server, location

Sets the value of the Last-Modified header returned on the response, by default the module does not return a Last-Modified header. The reason for having this parameter here is in order to support If-Modified-Since / If-Unmodified-Since. Since nginx's builtin ngx_http_not_modified_filter_module runs before any other header filter module, it will not see any headers set by add_headers / more_set_headers. This makes nginx always reply as if the content changed (412 for If-Unmodified-Since / 200 for If-Modified-Since) For changing live content (e.g. live DASH MPD), Last-Modified is set to the current server time.

vod_last_modified_types

• syntax: vod_last_modified_types mime-type1 mime-type2 ...
• default: none
• context: http, server, location

Sets the MIME types for which the Last-Modified header should be set. The special value "*" matches any MIME type.

Configuration directives - DRM

vod_drm_enabled

• syntax: vod_drm_enabled on/off
• default: off
• context: http, server, location

When enabled, the module encrypts the media segments according to the response it gets from the drm upstream. Currently supported only for dash and mss (play ready).

vod_drm_clear_lead_segment_count

• syntax: vod_drm_clear_lead_segment_count count
• default: 1
• context: http, server, location

Sets the number of clear (unencrypted) segments in the beginning of the stream. A clear lead enables the player to start playing without having to wait for the license response.

vod_drm_max_info_length

• syntax: vod_drm_max_info_length length
• default: 4K
• context: http, server, location

Sets the maximum length of a drm info returned from upstream.

vod_drm_upstream_location

• syntax: vod_drm_upstream_location location
• default: none
• context: http, server, location

Sets the nginx location that should be used for getting the DRM info for the file.

vod_drm_info_cache

• syntax: vod_drm_info_cache zone_name zone_size [expiration]
• default: off
• context: http, server, location

Configures the size and shared memory object name of the drm info cache.

vod_drm_request_uri

• syntax: vod_drm_request_uri uri
• default: $vod_suburi
• context: http, server, location

Sets the uri of drm info requests, the parameter value can contain variables. In case of multi url, $vod_suburi will be the current sub uri (a separate drm info request is issued per sub URL)

Configuration directives - DASH

vod_dash_absolute_manifest_urls

• syntax: vod_dash_absolute_manifest_urls on/off
• default: on
• context: http, server, location

When enabled the server returns absolute URLs in MPD requests

vod_dash_manifest_file_name_prefix

• syntax: vod_dash_manifest_file_name_prefix name
• default: manifest
• context: http, server, location

The name of the MPD file (an mpd extension is implied).

vod_dash_profiles

• syntax: vod_dash_profiles profiles
• default: urn:mpeg:dash:profile:isoff-main:2011
• context: http, server, location

Sets the profiles that are returned in the MPD tag in manifest responses.

vod_dash_init_file_name_prefix

• syntax: vod_dash_init_file_name_prefix name
• default: init
• context: http, server, location

The name of the MP4 initialization file (an mp4 extension is implied).

vod_dash_fragment_file_name_prefix

• syntax: vod_dash_fragment_file_name_prefix name
• default: frag
• context: http, server, location

The name of the fragment files (an m4s extension is implied).

vod_dash_manifest_format

• syntax: vod_dash_manifest_format format
• default: segmenttimeline
• context: http, server, location

Sets the MPD format, available options are:

• segmentlist - uses SegmentList and SegmentURL tags, in this format the URL of each fragment is explicitly set in the MPD
• segmenttemplate - uses SegmentTemplate, reporting a single duration for all fragments
• segmenttimeline - uses SegmentTemplate and SegmentTimeline to explicitly set the duration of the fragments

Configuration directives - HDS

vod_hds_manifest_file_name_prefix

• syntax: vod_hds_manifest_file_name_prefix name
• default: manifest
• context: http, server, location

The name of the HDS manifest file (an f4m extension is implied).

vod_hds_fragment_file_name_prefix

• syntax: vod_hds_fragment_file_name_prefix name
• default: frag
• context: http, server, location

The prefix of fragment file names, the actual file name is frag-f<file-index>-v<video-track-index>-a<audio-track-index>-Seg1-Frag<index>.

vod_hds_generate_moof_atom

• syntax: vod_hds_generate_moof_atom on/off
• default: on
• context: http, server, location

When enabled the module generates a moof atom in the HDS fragments, when disabled only an mdat atom is generated. Turning this parameter off reduces the packaging overhead, however the default is on since Adobe tools are generating this atom.

Configuration directives - HLS

vod_hls_encryption_method

• syntax: vod_hls_encryption_method method
• default: none
• context: http, server, location

Sets the encryption method of HLS segments, allowed values are: none (default), aes-128, sample-aes.

vod_hls_absolute_master_urls

• syntax: vod_hls_absolute_master_urls on/off
• default: on
• context: http, server, location

When enabled the server returns absolute playlist URLs in master playlist requests

vod_hls_absolute_index_urls

• syntax: vod_hls_absolute_index_urls on/off
• default: on
• context: http, server, location

When enabled the server returns absolute segment URLs in media playlist requests

vod_hls_absolute_iframe_urls

• syntax: vod_hls_absolute_iframe_urls on/off
• default: off
• context: http, server, location

When enabled the server returns absolute segment URLs in iframe playlist requests

vod_hls_master_file_name_prefix

• syntax: vod_hls_master_file_name_prefix name
• default: master
• context: http, server, location

The name of the HLS master playlist file (an m3u8 extension is implied).

vod_hls_index_file_name_prefix

• syntax: vod_hls_index_file_name_prefix name
• default: index
• context: http, server, location

The name of the HLS media playlist file (an m3u8 extension is implied).

vod_hls_iframes_file_name_prefix

• syntax: vod_hls_iframes_file_name_prefix name
• default: iframes
• context: http, server, location

The name of the HLS I-frames playlist file (an m3u8 extension is implied).

vod_hls_segment_file_name_prefix

• syntax: vod_hls_segment_file_name_prefix name
• default: seg
• context: http, server, location

The prefix of segment file names, the actual file name is seg-<index>-v<video-track-index>-a<audio-track-index>.ts.

vod_hls_encryption_key_file_name

• syntax: vod_hls_encryption_key_file_name name
• default: encryption.key
• context: http, server, location

The name of the encryption key file name, only relevant when encryption method is not none.

vod_hls_encryption_key_uri

• syntax: vod_hls_encryption_key_uri uri
• default: a url pointing to encryption.key
• context: http, server, location

Sets the value of the URI attribute of EXT-X-KEY, only relevant when encryption method is not none. The parameter value can contain variables.

vod_hls_encryption_key_format

• syntax: vod_hls_encryption_key_format format
• default: none
• context: http, server, location

Sets the value of the KEYFORMAT attribute of EXT-X-KEY, only relevant when encryption method is not none.

vod_hls_encryption_key_format_versions

• syntax: vod_hls_encryption_key_format_versions versions
• default: none
• context: http, server, location

Sets the value of the KEYFORMATVERSIONS attribute of EXT-X-KEY, only relevant when encryption method is not none.

vod_hls_interleave_frames

• syntax: vod_hls_interleave_frames on/off
• default: off
• context: http, server, location

When enabled, the HLS muxer interleaves frames of different streams (audio / video). When disabled, on every switch between audio / video the muxer flushes the MPEG TS packet.

vod_hls_align_frames

• syntax: vod_hls_align_frames on/off
• default: on
• context: http, server, location

When enabled, every video / audio frame is aligned to MPEG TS packet boundary, padding is added as needed.

Configuration directives - MSS

vod_mss_manifest_file_name_prefix

• syntax: vod_mss_manifest_file_name_prefix name
• default: manifest
• context: http, server, location

The name of the manifest file (has no extension).

Nginx variables

The module adds the following nginx variables:

• $vod_suburi - the current sub uri. For example, if the url is: http://<domain>/<location>/<prefix>,<middle1>,<middle2>,<middle3>,<postfix>.urlset/<filename> $vod_suburi will have the value http://<domain>/<location>/<prefix><middle1><postfix>/<filename> when processing the first uri.
• $vod_filepath - in local / mapped modes, the file path of current sub uri. In remote mode, has the same value as $vod_suburi.

Note: Configuration directives that can accept variables are explicitly marked as such.

Sample configurations

Local configuration

http {
	upstream fallback {
		server fallback.kaltura.com:80;
	}

	server {
		# vod settings
		vod_mode local;
		vod_fallback_upstream_location /fallback;
		vod_last_modified 'Sun, 19 Nov 2000 08:52:00 GMT';
		vod_last_modified_types *;

		# vod caches
		vod_metadata_cache metadata_cache 512m;
		vod_response_cache response_cache 128m;
		
		# gzip manifests
		gzip on;
		gzip_types application/vnd.apple.mpegurl;

		# file handle caching / aio
		open_file_cache          max=1000 inactive=5m;
		open_file_cache_valid    2m;
		open_file_cache_min_uses 1;
		open_file_cache_errors   on;
		aio on;
		
		location ^~ /fallback/ {
			internal;
			proxy_pass http://fallback/;
			proxy_set_header Host $http_host;
		}

		location /content/ {
			root /web/;
			vod hls;
			
			add_header Access-Control-Allow-Headers '*';
			add_header Access-Control-Expose-Headers 'Server,range,Content-Length,Content-Range';
			add_header Access-Control-Allow-Methods 'GET, HEAD, OPTIONS';
			add_header Access-Control-Allow-Origin '*';
			expires 100d;
		}
	}
}

Mapped configuration

http {
	upstream kalapi {
		server www.kaltura.com:80;
	}

	upstream fallback {
		server fallback.kaltura.com:80;
	}

	server {
		# vod settings
		vod_mode mapped;
		vod_upstream_location /kalapi;
		vod_upstream_extra_args "pathOnly=1";
		vod_fallback_upstream_location /fallback;
		vod_last_modified 'Sun, 19 Nov 2000 08:52:00 GMT';
		vod_last_modified_types *;

		# vod caches
		vod_metadata_cache metadata_cache 512m;
		vod_response_cache response_cache 128m;
		vod_path_mapping_cache mapping_cache 5m;
		
		# gzip manifests
		gzip on;
		gzip_types application/vnd.apple.mpegurl;

		# file handle caching / aio
		open_file_cache          max=1000 inactive=5m;
		open_file_cache_valid    2m;
		open_file_cache_min_uses 1;
		open_file_cache_errors   on;
		aio on;
		
		location ^~ /fallback/ {
			internal;
			proxy_pass http://fallback/;
			proxy_set_header Host $http_host;
		}

		location ^~ /kalapi/ {
			internal;
			proxy_pass http://kalapi/;
			proxy_set_header Host $http_host;
		}

		location ~ ^/p/\d+/(sp/\d+/)?serveFlavor/ {
			# encrypted hls
			vod hls;
			vod_secret_key "mukkaukk$vod_filepath";
			vod_hls_encryption_method aes-128;
			
			add_header Access-Control-Allow-Headers '*';
			add_header Access-Control-Expose-Headers 'Server,range,Content-Length,Content-Range';
			add_header Access-Control-Allow-Methods 'GET, HEAD, OPTIONS';
			add_header Access-Control-Allow-Origin '*';
			expires 100d;
		}
	}
}

Remote configuration

http {
	upstream kalapi {
		server www.kaltura.com:80;
	}

	server {
		# vod settings
		vod_mode remote;
		vod_upstream_location /kalapi;
		vod_last_modified 'Sun, 19 Nov 2000 08:52:00 GMT';
		vod_last_modified_types *;

		# vod caches
		vod_metadata_cache metadata_cache 512m;
		vod_response_cache response_cache 128m;
		
		# gzip manifests
		gzip on;
		gzip_types application/vnd.apple.mpegurl;

		# file handle caching / aio
		open_file_cache          max=1000 inactive=5m;
		open_file_cache_valid    2m;
		open_file_cache_min_uses 1;
		open_file_cache_errors   on;
		aio on;
		
		location ^~ /kalapi/ {
			internal;
			proxy_pass http://kalapi/;
			proxy_set_header Host $http_host;
		}

		location ~ ^/p/\d+/(sp/\d+/)?serveFlavor/ {
			vod hls;
			
			add_header Access-Control-Allow-Headers '*';
			add_header Access-Control-Expose-Headers 'Server,range,Content-Length,Content-Range';
			add_header Access-Control-Allow-Methods 'GET, HEAD, OPTIONS';
			add_header Access-Control-Allow-Origin '*';
			expires 100d;
		}
	}
}

Copyright & License

All code in this project is released under the AGPLv3 license unless a different license for a particular library is specified in the applicable library path.

Copyright © Kaltura Inc. All rights reserved.