Mastering SCTE-35 and SCTE-104: key standards for broadcast ad insertion and content control

Imagine this: You’re watching a live football game, and the score is tied as the first half nears its end. The tension is palpable as your team pushes forward, seconds away from a critical goal. Suddenly, just as the play unfolds, the screen cuts to a commercial break. You’re left staring at an ad instead of the game’s decisive moment. It’s frustrating, right?

Fortunately, this scenario doesn’t happen, thanks to ad markers like SCTE-35. These markers ensure that ads are inserted at precisely the right moments, never interrupting the action at crucial times. Without them, the viewing experience would be chaotic, with ads potentially cutting into the most important parts of the broadcast. The Society of Cable Telecommunications Engineers (SCTE) developed SCTE-35 and SCTE-104 markers to automate content insertion in TV broadcasting, making it possible to deliver the right ads to the right audience without disrupting the broadcast. These standards are supported by most professional streaming tools, including Flussonic Media Server.

In this article, we’ll explain how SCTE-35 and SCTE-104 ad markers work together to achieve seamless and accurate ad insertion during broadcasts.

Understanding SCTE-35 and SCTE-104 ad markers

SCTE-35 and SCTE-104 are both standards developed by SCTE to facilitate automated content signaling and insertion in broadcast workflows. While they serve different functions within the signal chain, this markers are closely related and often work together to enable precise control over broadcast content.

SCTE-35 is used within the MPEG transport stream to signal events like starting or stopping an ad break, directly affecting what is broadcast to viewers. SCTE-104 works earlier in the broadcast process, where it sends instructions to video routers and automation systems. These instructions are later converted into SCTE-35 messages for final transmission.

Consider a broadcaster airing the Super Bowl. The network needs to deliver different advertisements to viewers in different regions, maximizing ad revenue by tailoring content to local audiences.

Using SCTE-35 and SCTE-104 ad markers, the network’s broadcast automation system generates precise SCTE-104 commands that signal when and where ads should be inserted. These commands are sent to the video routers and automation systems that handle the video signals before they’re encoded for transmission. As the live event is broadcast, these SCTE104 commands are converted into SCTE-35 markers, embedded in the MPEG transport stream by video encoders.

When the stream reaches regional affiliates, these SCTE-35 markers instruct local ad splicers to insert specific regional ads at the right moments—whether during a commercial break, halftime show, or other programmed events. This process allows the network to deliver the right ads to the right audiences without interrupting the live event, ensuring a seamless viewing experience.

SCTE-35: Technical Details

SCTE-35 is a digital program insertion (DPI) standard used to signal and control various events within an MPEG transport stream. It was built originally to insert local content in the transport streams. You can see it’s specification on the site.

The standard defines a structure for signaling the insertion of content into a broadcast stream. This structure includes several key components:

• Splice Info Section: The core component of an SCTE35 message, containing detailed instructions for the insertion or deletion of content.
• Splice Insert: A command within the SCTE35 message that tells the decoder to insert specific content at a designated splice point.
• Time Signal: A feature that allows precise timing of events, ensuring that content is inserted or removed at exactly the right moment.

Originally designed specifically for ad insertions, SCTE-35 marker is highly versatile and can also be used in other areas, such as rights management and programming.

In practice, SCTE-35 messages are generated by broadcast automation systems or ad insertion servers and then embedded in the broadcast stream by video encoders or multiplexers. These messages carry instructions for content manipulation, such as when to start an ad break or switch from the main program to different content (for example, regional feed).

The automation system sends a command to the ad server, which then generates an SCTE-35 message. This message is inserted into the MPEG transport stream by the video encoder or multiplexer, instructing downstream devices, such as ad splicers, to insert a specific regional advertisement. Once the ad break is over, another SCTE35 message signals the return to the main program.

This process allows broadcasters to automate content insertion, reducing the need for manual intervention and ensuring consistency across different regions and platforms. However, implementing SCTE-35 can present challenges, such as ensuring accurate timing and troubleshooting signal issues. Broadcasters often need to fine-tune their systems to ensure that SCTE-35 messages are processed correctly and that content is inserted seamlessly.

SCTE-104: Technical Details

SCTE-104 is a standard used at an early stage in the video signal process, where the video is still in its original, raw form before it’s compressed or prepared for transmission. This stage is often referred to as the “baseband video domain.” At this point, SCTE-104 provides a set of commands that are eventually converted into SCTE35 messages, which are used later when the video is transmitted. The structure of SCTE-104 packets includes:

• Message Types: SCTE-104 supports various message types, such as splice requests, time signals, and commands for managing content markers.
• Command Components: These include instructions for content insertion, deletion, and the management of ad breaks.

SCTE-104 messages are typically generated by video routers, automation systems, or other equipment that controls the video signal before it is encoded into an MPEG stream. Mapping SCTE-104 to SCTE-35 involves converting cue points and instructions from the baseband format (SCTE-104) to the MPEG transport stream (SCTE-35).

As shown in the diagram below, this mapping ensures a continuous flow between both standards. This process is typically how encoders generate the markers.

In a broadcast operation, SCTE-104 messages are used to manage the video signal before it enters the transport stream. For example, during a live event, an SCTE-104 message might be sent from a video router to signal the start of an ad break. This message is then translated into an SCTE-35 command that triggers the ad insertion within the MPEG stream.

SCTE ad markers integration with HLS (HTTP Live Streaming)

SCTE-35 markers are also used in HTTP Live Streaming (HLS), a widely adopted streaming protocol for delivering video content over the internet. In HLS, SCTE-35 markers signal ad breaks and content switching within the stream. This allows broadcasters to insert ads and manage content in real-time across various devices, including smartphones, tablets, smart TVs, and web browsers. This capability is important for broadcasters who need to deliver targeted content to viewers on multiple devices. This integration is well-documented in HLS specifications, making it easier to implement SCTE-35 markers in HLS streaming solutions.

Conclusion

SCTE-35 and SCTE-104 are essential tools for modern broadcasters, enabling them to manage content insertion and signaling with precision and efficiency. To fully leverage these standards, it’s crucial to use tools and hardware that support and process these markers effectively. For instance, Flussonic Media Server works with markers in the SCTE-35, SCTE-104, and AWS formats, recognizing the metadata associated with splice_insert events.

Flussonic can read these ad marker formats from different types of streams and, when the input and output stream formats are the same, it passes the markers through without changes. If the output format differs, Flussonic can convert the ad insertion markers from the input stream into another format and pass them along to the output stream. This capability ensures that ad insertion and content control are handled seamlessly, regardless of the format or platform.

To see how Flussonic can work for you, try our trial version and experience these capabilities firsthand.