Mainstream production codecs are usually applied in file-based exchange at the broadcaster’s content creation side but ideally also between different broadcasters without having a transcoding in between. By introducing UHDTV in content creation (production) a number of different image/video formats became available: the move to progressive scan formats at various frame-rates including 1080p; an increased spatial resolution 3840x2160p (UHDTV-1), the introduction of two HDR transfer characteristics called HLG and PQ according to ITU-R BT.2100 (in addition SDR Gamma), and the introduction of wide colour space as defined in ITU-R BT.2020.
Manufactures of production codecs are challenged by the variety of image format options to select the compression algorithm and to set the right operating points (e.g. bit rate, bit depth, features like sub-sampling, GOP structures). Users are challenged in a similar way to select the right codec offered by manufactures and to understand the trade-off between bit rate, image quality (multi-generation), and many more parameters.
The EBU (representing 117 broadcasters world-wide) has tasked its Video Systems Project group together with the German group “Beyond HD/Production Codecs” to evaluate the performance and the image quality headroom provided by UHDTV production codecs and compression algorithms. The focus was on the native implementations of the well-known codecs of Apple (ProRes), Avid (DNxHR), Panasonic (AVCUltra) and Sony (XAVC) as these codecs are used directly in camcorders or within the production workflows. Due to the variety of combinations of features and codecs (in total more than 200) a majority voting between the EBU Members has been performed with the result that 45 combinations were finally tested by performing an experts viewing session at IRT in Munich as well as an objective assessment (PSNR). For all tests multi-generation behaviour (including pixel shift) has been performed.
The SMPTE presentation will provide the full approach of the tests. It will include the creation of source sequences with all combinations of colour space, resolution, transfer function, frame rate; the approach of the image quality analysis by cascading the codecs seven times including a pixel shift in between and the subjective assessment methodology to evaluate the image quality in the experts viewing sessions. The presentation results will encourage broadcast and industry experts to follow the methodologies applied and to perform similar tests, leading to a broad understanding of UHDTV roll-out in production workflows.
Technical Depth of Presentation
General knowledge about video compression, UHD parameters, production codecs workflows are welcomed.
The technical depth is inbetween fundamental and intermediate.
What Attendees will Benefit Most from this Presentation
1. Choice of production codec is a trade-off between bit rate, quality requirements, supported features, costs
2. Defining basic conditions and testing implementations can save costs
3. Use standardised/well-described experts viewings