The need for mezzanine encoding

Silhouette of a TV Camera filming a live broadcast

Linear contribution

Live broadcasters are focusing more on premium sport and live event content where live linear delivery is essential. Effective contribution of premium content such as live sport events requires rock-solid, reliable operation, high quality video and low latency transmission. To meet these requirements, operators are increasingly acquiring content directly from content providers. Content contribution is either over dedicated IP links directly into the transcoder cloud or over public internet using SRT, Zixi or RIST.
As the distribution market moves to transcoding of content in a private or public cloud, it creates challenges around how content is ingested into the cloud while maintaining high quality, low distribution cost and low delay. Uncompressed HD and 4K video signals created in the contribution phase generate huge data volumes. Sending uncompressed video into a cloud can be costly due to the high bandwidth required between content owner and cloud installation, combined with the processing cost of ingesting uncompressed video. Bit-rate and quality must be balanced against operational costs.

Content contribution and head-end operations

Recent years have seen marked shift from dedicated head-end operations using hardware encoding, to a “cloudification” of operations, that deploy software encoding in a mix of in-house private, outsourced public or private, and hybrid cloud solutions.
To meet the demands for high quality and low delay while maintaining acceptable operational cost when ingesting source content into the cloud will require placing a mezzanine encoder at the content owner (typically the broadcaster). The choice of coder technology will typically depend on bandwidth available between content owner and cloud installation, combined with supported decoder standards in the cloud. If high bandwidth is available between the sites it might be most efficient to use lighter codecs such as JPEG XS (assuming the cloud installation supports decoding of JPEG XS). However, it is more likely that AVC or HEVC will be used, typically configured to around twice the bit-rate provided to the end user, combined with 4:2:2 and 10 bit of supported in the transcoder.

Mezzanine encoding: Hardware vs. Software

There are several factors that determine how mezzanine coding is deployed, and alongside, several considerations when planning these deployments.

First, determining factors. Placing mezzanine encoding in the cloud would incur high data transfer cost as it ingests uncompressed video from the content provider. Instead, equipment must be deployed remotely, directly at or with the content providers themselves, and at multiple sites.

Deployment should be as simple as “install and forget” and so to meet expectations for premium content, reliable operation with built-in redundancy handling and minimum downtime is required, with one-time, fixed configuration.

Second, considerations. Configuration will depend on factors such as available bandwidth between content provider and cloud, latency requirements and limits, the choice of codecs, video resolutions and HDR requirements, the number of channels required, and source format.

With those considerations and determining factors taken into account, the next decision to make is whether to pursue hardware or software encoding. There are of course extensive pros and cons to each, but generally hardware encoding outweighs software encoding pros; dedicated hardware encoding has lower delay, with higher data rates and higher quality, has greater rack density, is more easily configured, and uses less power per channel and per rack unit. Dedicated hardware is more secure since it can only be used for encoding, minimizing the need for software patches and their potential vulnerabilities. Keeping in mind that even if the codec technologies changes, the cloud transcoder installation will be backward compatible to decode previous coder standards. Consequently, the mezzanine encoder system does not need to be upgraded when coder standards are upgraded in the cloud transcoding system.

Premium and live content deserves and demands to be handled with premium technology and the choices that operators take can play a huge part in resulting quality and cost.

Careful consideration is therefore essential and Appear is committed to providing its customers with the best advice and technology available.