How SMPTE Evaluates AV1 for Contribution Links

The Society of Motion Picture and Television Engineers (SMPTE) evaluates the AOMedia Video 1 (AV1) codec for contribution links by rigorously testing its compression efficiency, picture quality preservation, latency performance, and resilience across multi-generation encoding cycles. While AV1 was originally designed primarily for internet distribution, professional broadcast contribution—transmitting pristine video from live venues or studios to production facilities—demands distinct operational standards. SMPTE’s assessment framework determines whether AV1 can meet these demanding broadcast mezzanine requirements compared to established contribution codecs like JPEG XS, AVC-Intra, and HEVC.

Profile and Chroma Subsampling Compliance

Broadcast contribution environments require high color fidelity to survive downstream post-production, color grading, and chroma keying. SMPTE focuses its evaluation on AV1’s Professional Profile, which supports:

10-bit and 12-bit depth: Preserving dynamic range and preventing banding in High Dynamic Range (HDR) workflows.
4:2:2 and 4:4:4 Chroma Subsampling: Standard broadcast contribution relies heavily on 4:2:2 color representation. SMPTE evaluates how effectively AV1 encoders process 4:2:2 content without downsampling artifacts or color bleeding.

Multi-Generation Concatenation Resilience

A critical requirement for contribution links is multi-generation robustness. Footage sent over a contribution link is frequently decoded, edited, composited, and re-encoded several times before reaching the viewer. SMPTE assesses AV1 by running concatenation tests:

A pristine master clip is encoded with AV1 at a target contribution bitrate.
The stream is decoded to uncompressed video.
The process is repeated over multiple generations (typically 3 to 7 passes).
The final output is measured against the original to evaluate generational loss, checking for compounding compression artifacts such as edge ringing, blocking, or texture smoothing.

Latency and Processing Complexity

Contribution feeds for live sports, news, and remote production (REMI) demand low-latency workflows. SMPTE analyzes AV1's encoding profiles under strict real-time constraints:

Intra-Only Coding: Testing AV1 in intra-frame-only modes to eliminate inter-frame dependencies, reducing encoding/decoding buffer latency to sub-frame or single-frame levels.
Hardware Implementation Viability: AV1 is computationally complex. SMPTE tracks hardware encoder acceleration and FPGA implementations to verify that real-time 4K and 8K 60fps contribution can be achieved with manageable power and thermal envelopes in outside broadcast (OB) trucks and field transmitters.

Objective and Subjective Quality Methodologies

SMPTE employs standardized measurement procedures to benchmark AV1 against codecs such as HEVC, AVC, and JPEG XS:

Subjective Assessment: Utilizing ITU-R BT.500 methodologies, expert panels evaluate clips under controlled lighting and display environments using Double Stimulus Continuous Quality Scale (DSCQS) testing.
Objective Metrics: Analysis using peak signal-to-noise ratio (PSNR), structural similarity index (SSIM), and Video Multi-Method Assessment Fusion (VMAF) across standardized broadcast test sequences featuring high grain, fast motion, and complex textures.
Bjøntegaard Delta (BD-Rate): Calculating the average bitrate savings of AV1 relative to reference contribution codecs at equivalent visual quality levels.

Standards Interoperability and Transport Mapping

For AV1 to function in professional contribution workflows, it must integrate into standardized broadcast infrastructure. SMPTE evaluates how AV1 bitstreams map into existing transmission standards, including:

SMPTE ST 2110: Encapsulation of compressed video over professional IP networks (specifically SMPTE ST 2110-22 for constant bitrate compressed streams).
Material Exchange Format (MXF): Defining descriptive metadata and standardizing AV1 payload wrapping in MXF containers for broadcast storage, exchange, and playout servers.