Origin Redundancy

When an HTTP-based CDN or cache system supports origin failover for high availability (HA), OvenMediaEngine Enterprise, acting as an origin server, provides redundancy features that enable both the Main and Backup Servers to deliver identical content.

When a CDN supports origin failover, it automatically switches to the backup server if a failure occurs on the Main Server. To support this, the Main and Backup Servers must provide identical content in the same manner. This guide explains how OvenMediaEngine Enterprise, installed on different servers, can be configured to provide the same Low-Latency HLS (LL-HLS) and HLS content.

TimestampMode Settings | 0.18.3.0+

TimestampMode is a feature for aligning stream timestamps. OvenMediaEngine Enterprise provides three timestamp modes to ensure that the Main and Backup Servers can generate identical content:

Value

Description

ZeroBased

* Default

Starts stream timestamps from 0.

SystemClock

Sets timestamps based on the server's system clock.

Original

Uses the original timestamps generated by the external encoder without modification.

This feature addresses the issue that occurs when an external encoder sends a stream to OvenMediaEngine Enterprise with timestamps that are not based on the wall clock (typically starting from zero). In such cases, the Main and Backup Servers may generate LL-HLS or HLS content with different timestamps depending on when the stream starts.

Even if the Main and Backup Servers start at the same time initially, restarting one of them typically resets its timestamps to zero. This leads to a mismatch between the servers’ timestamps. As a consequence, when the CDN switches between the Main and Backup Servers, the player may encounter discontinuous timestamp jumps, which can cause playback issues for LL-HLS or HLS streams.

To prevent this, it is important to configure the appropriate TimestampMode so that the Main and Backup Servers generate matching timestamps:

If the encoder uses wall clock–based timestamps (e.g., AWS Elemental Live, FFmpeg): <TimestampMode>Original</TimestampMode>
If the encoder generates timestamps independently of the wall clock (e.g., OBS starts from zero): <TimestampMode>SystemClock</TimestampMode>

When using the SystemClock mode, OvenMediaEngine Enterprise sets timestamps based on the server's system clock. Therefore, the system time on Main and Backup Servers must be precisely synchronized.

If you are unsure of how the encoder generates timestamps, it is recommended to use the SystemClock mode to ensure timestamp consistency between servers.

TimestampMode Example

To use this feature, configure <TimestampMode> under <Providers><[Protocol Name]> in Server.xml as shown below:

<?xml version="1.0" encoding="UTF-8"?>
<Server version="8">
  ...
  <VirtualHosts>
    <VirtualHost>
      <Applications>
        <Application>
          <Providers>
            <OVT>
              <TimestampMode>SystemClock</TimestampMode> <!-- Original, ZeroBased -->
            </OVT>
            <RTMP>
              <TimestampMode>SystemClock</TimestampMode> 
            </RTMP>
            <WebRTC>
              <TimestampMode>SystemClock</TimestampMode>
            </WebRTC>
            <RTSPPull>
              <TimestampMode>SystemClock</TimestampMode>
            </RTSPPull>
            <SRT>
              <TimestampMode>SystemClock</TimestampMode>
            </SRT>
            <Schedule>
              <TimestampMode>SystemClock</TimestampMode>
              <MediaRootDir>schedule</MediaRootDir>
              <ScheduleFilesDir>schedule</ScheduleFilesDir>
            </Schedule>
          </Providerrs>
        </Application>
      </Applications>
    </VirtualHost>
  </VirtualHosts>
  ...
</Server>

ServerTimeBasedSegmentNumbering Settings

ServerTimeBasedSegmentNumbering is a feature for matching segment numbers.

OvenMediaEngine Enterprise provides the ServerTimeBasedSegmentNumbering option, which allows HLS or LL-HLS segment numbers (sequence numbers) to be generated based on the server’s system clock. This ensures that segments from the Main and Backup Servers are assigned the same sequence numbers, regardless of when the streams are started.

When using the ServerTimeBasedSegmentNumbering feature, the following settings for LL-HLS or HLS must be identical on both servers:

ChunkDuration
SegmentDuration
SegmentCount

In addition, the stream's FPS and Keyframe Interval must also be configured identically.

ServerTimeBasedSegmentNumbering Example

To enable this feature, configure <ServerTimeBasedSegmentNumbering> under <Publishers><LLHLS> (or <Publishers><HLS>) in Server.xml as shown below:

<?xml version="1.0" encoding="UTF-8"?>
<Server version="8">
  ...
  <VirtualHosts>
    <VirtualHost>
      <Applications>
        <Application>
          <Publishers>
            ...
            <LLHLS>
              <OriginMode>true</OriginMode>
              <ServerTimeBasedSegmentNumbering>true</ServerTimeBasedSegmentNumbering>
              <ChunkDuration>1</ChunkDuration>
              <PartHoldBack>3</PartHoldBack>
              <SegmentDuration>6</SegmentDuration>
              <SegmentCount>10</SegmentCount>
              <CrossDomains>
                <Url>*</Url>
              </CrossDomains>
            </LLHLS>
            <HLS>
              <SegmentCount>10</SegmentCount>
              <SegmentDuration>4</SegmentDuration>
              <ServerTimeBasedSegmentNumbering>true</ServerTimeBasedSegmentNumbering>
              <CrossDomains>
                <Url>*</Url>
              </CrossDomains>
            </HLS>
            ...
          </Publishers>
        </Application>
      </Applications>
    </VirtualHost>
  </VirtualHosts>
  ...
</Server>

What is OriginMode?

When OriginMode is enabled, OvenMediaEngine Enterprise does not issue a unique session key for each player session and disables session-based access control features. As a result, all users receive content using the same URL and structure, allowing cache servers to properly cache LL-HLS or HLS content.

By default, OvenMediaEngine Enterprise issues a session key for each player session and performs access control based on it. However, from the perspective of a cache server, this causes the content to be segmented by session, making caching impossible. Therefore, when using OvenMediaEngine Enterprise as the origin server behind a cache server, OriginMode should be enabled to allow the cache server to properly cache the content.

When OriginMode is enabled, the responsibility for access control shifts from the origin server to the cache server. This means that the cache server must implement its own authentication and authorization logic to restrict access to content.

PacketSilenceTimeoutMs Settings | 0.18.3.0+

PacketSilenceTimeoutMs is a feature that detects and terminates unresponsive streams.

To identify and remove streams that stop receiving packets for a certain period of time, OvenMediaEngine Enterprise provides the PacketSilenceTimeoutMs setting. When this setting is enabled, if no packets are received within the specified timeout, the stream is automatically terminated and an appropriate HTTP error status (such as 404) is returned. This allows the CDN to detect a failure on the Main Server and initiate failover to the Backup Server.

Some encoders may maintain the connection but stop sending packets for a period of time. This can happen in normal scenarios, such as when a variable-FPS encoder sends a still frame, or due to abnormal conditions like TCP connection issues or encoder failures. Since OvenMediaEngine Enterprise continues to maintain the stream in such cases without returning an HTTP error, the CDN may be unable to detect the problem.

The PacketSilenceTimeoutMs setting is supported by the following Providers:

RTMP
SRT
WebRTC
Multiplex

ScheduledChannel is a persistent channel, so even if no packets are received, the stream is not deleted. Instead, it transitions to the configured FallbackProgram.

PacketSilenceTimeoutMs Example

To use this feature, configure <PacketSilenceTimeoutMs> under <Providers><[Protocol Name]> in Server.xml as shown below:

<?xml version="1.0" encoding="UTF-8"?>
<Server version="8">
  ...
  <VirtualHosts>
    <VirtualHost>
      <Applications>
        <Application>
          <Providers>
            <RTMP>
            <TimestampMode>SystemClock</TimestampMode>
              <PacketSilenceTimeoutMs>1000</PacketSilenceTimeoutMs>
            </RTMP>
            <MPEGTS>
              <TimestampMode>SystemClock</TimestampMode>
              <PacketSilenceTimeoutMs>1000</PacketSilenceTimeoutMs>
            </MPEGTS>
            <SRT>
              <TimestampMode>SystemClock</TimestampMode>
              <PacketSilenceTimeoutMs>1000</PacketSilenceTimeoutMs>
            </SRT>
            <WebRTC>
              <TimestampMode>SystemClock</TimestampMode>
              <PacketSilenceTimeoutMs>1000</PacketSilenceTimeoutMs>
            </WebRTC>
            <Multiplex>
              <MuxFilesDir>mux_files</MuxFilesDir>
              <PacketSilenceTimeoutMs>1000</PacketSilenceTimeoutMs>
            </Multiplex>
          </Providerrs>
        </Application>
      </Applications>
    </VirtualHost>
  </VirtualHosts>
  ...
</Server>

For Pull-based Providers such as RTSP and OVT, a similar functionality is already provided through the noInputFailoverTimeoutMs setting.

Reference: https://docs.ovenmediaengine.com/rest-api/v1/virtualhost/application/stream#create-stream-pull

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Last updated 4 days ago