Source failover is a setup that involves two redundant sources for a transport stream flow. This redundancy helps to minimize disruption to your video stream. To use source failover, you specify two sources for the flow, then choose one of two options for the failover mode: Merge or Failover.
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Merge mode combines the sources into a single stream, allowing a graceful recovery from any single-source loss. If you set the failover mode to Merge, you can set the recovery window, which is the size of the buffer (delay) that you want MediaConnect to maintain. A larger recovery window means a longer delay in transmitting the stream, but more room for error correction. A smaller recovery window means a shorter delay, but less room for error correction. Sources used this way need to be binary identical, which means that they need to have originated from the same encoder. MediaConnect must also receive content from the two sources at the same time. Additionally, if the sources use RTP protocol, they must have RTP headers with aligned sequence numbers and they must also comply with the SMPTE ST 2022-7 standard.
Note
SMPTE ST 2022-7 is a standard developed by the Society of Motion Picture and Television Engineers (SMPTE) group. The ST 2022-7 standard defines a method that replaces missing packets with packets in an identical, redundant stream. This type of failover requires a small latency buffer in your workflow to allow time for MediaConnect to recover packets from the two streams.
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Failover mode allows switching between a primary and a backup stream. This switching facilitates an easy transition to a more reliable stream. If you set the failover mode to Failover, you can specify a source as the primary source. The second source serves as the backup. If you don’t specify a primary source, MediaConnect treats both sources with equal priority, and switches to the available source as needed.
MediaConnect uses the two modes of failover in the following ways:
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In the Merge mode, MediaConnect uses content from both sources. The flow randomly selects one of the sources to start with. If that source is missing a packet, the flow pulls the missing packet from the other source. For example, if the flow is using source A and packet 123 is missing, MediaConnect pulls in packet 123 from source B and continues using source A. In this mode, the two sources are binary identical/ST 2022-7 compliant.
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In the Failover mode, if you don't specify a primary source, MediaConnect randomly uses one of the sources to provide content for the flow. If MediaConnect does not receive data from the source for 500 milliseconds, the flow switches to the other source, and can continue switching back and forth between sources as needed. If you do specify a primary source, MediaConnect uses that source to provide content for the flow. The flow switches to the other source if the primary source does not send data for 500 milliseconds, and switches back to the primary source as soon as data returns.
Note
MediaConnect doesn't support source failover on CDI flows or on entitlement flows. For more information about creating redundancy with CDI flows, visit: Creating a CDI flow. Additionally, you cannot add a second source to an existing flow for failover if you are using the Zixi pull protocol.
Failover support for source protocols in MediaConnect
The following table describes which source protocols support failover.
| Protocol | Does this protocol support source failover? | How many sources can be added? | Supported failover modes |
|---|---|---|---|
| RIST | Yes | 2 | Merge or failover |
| RTP | Yes | 2 | Merge or failover |
| RTP-FEC | Yes | 2 | Merge or failover |
| SRT listener | Yes | 2 | Failover only |
| SRT caller | Yes | 2 | Failover only |
| Zixi pull | No | None - Zixi pull cannot be used as a source. | Source failover is not supported |
| Zixi push | Yes | 2 | Merge or failover |
| Zixi push for AWS Elemental Link UHD | Yes | 2 | Failover only |
| CDI | No | 1 | Source failover is not supported |
| ST 2110 JPEG XS | No | 1 | Source failover is not supported |
| Entitlement flows | No | 1 | Source failover is not supported |
