Introduction
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In this segment, we delve into real-time live content as well as pre-prepared file playout or VOD-to-live workflows. Both AWS Elemental Live (on-premises) and AWS Elemental MediaLive (cloud-based) support live HDR workflows up to UHD, with the capability to down-convert HDR to SDR. These platforms also enable the mixing of various HDR formats at the input stage, which can be advantageous for downstream processes.
Workflows
For cloud-based HDR workflows, AWS Elemental MediaLive can accept live sources through HLS, AWS Elemental MediaConnect flows, uncompressed AWS Cloud Digital Interface (AWS CDI) sources, or inputs from AWS Elemental Link, which supports 10-bit video. MP4 files stored in Amazon Simple Storage Service (Amazon S3) can loop or play out as part of a VOD-to-live workflow.
In on-premises HDR workflows, AWS Elemental Live can receive content via unicast, multicast, SDI, SMPTE ST 2110, SMPTE 2022-6, HLS, SRT, or directly from MediaConnect. Media files can be uploaded directly to AWS Elemental Live and then played out as inputs for your live event. Additionally, external devices like the AJA Ki Pro Ultra can manage file playout and send feeds to an AWS Elemental Live appliance via 3G SDI or quad-SDI for UHD sources.
Depending on the scale of your production, streaming live in HDR can present challenges that must be navigated to maintain color accuracy. Certain cameras, such as those from Blackmagic Designs, allow shooting in logarithmic format with a lookup table (LUT) applied directly in the camera, so the output is already PQ or HLG. In instances where LUT loading in the camera is unfeasible, customers can use devices like the AJA FS-HDR to manage the log to PQ/HLG/SDR conversion. This is also a valuable tool for enhancing on-set monitors, ensuring that the visual output aligns with the producers’ creative vision.
Dolby Vision – Workflow
Metadata
For outputs that comply with HDR10 or Dolby Vision, extracting MaxCLL and MaxFALL values is necessary. If playing out a file as a source, tools like DaVinci Resolve can be utilized to export HDR10 metadata after an HDR10+ inspection of each frame. The generated text file can then be reviewed for the required values.
In live streaming scenarios, this process is more of a “best effort.” Depending on your event, you can record rehearsals or capture footage of the sports field before the event starts, applying the same metadata extraction method.
To output Dolby Vision, the use of AWS Elemental Live is essential. Having integrated the Dolby Vision SDK, AWS Elemental Live can incorporate the necessary metadata into outputs when Dolby Vision Profile 5 or 8.1 is selected in the Preprocessors >> Color Corrector >> Color Space Conversion section. For further understanding, refer to this detailed exploration of Dolby Vision.
HEVC & AVC
When utilizing ABR protocols like HLS or DASH, it’s inadvisable to expect client players to switch between codecs. Many players, such as smart TVs or older USB stick devices, lack the CPU power to do so, leading to buffering or total stalls. Additionally, switching between HDR and SDR is not recommended. This presents a potential complication with HDR, necessitating a full HDR ABR ladder, a complete SDR ABR ladder, and potentially a third ladder if both HEVC and AVC are to be supported. This may involve deploying multiple AWS Elemental Lives for the same stack, requiring the Output Locking feature to coordinate outputs at the frame level. For more details, check out this guide on Output Locking. Furthermore, mixing HDR and SDR can introduce complications for SSAI, especially when ads are in SDR while the program is in HDR. Testing with all expected variations is crucial to guarantee smooth playback for your audience. Many TVs allow USB sticks to play video content, making it a simple way to verify your HDR settings.
HDR Product Support Reference
- AWS Elemental Live: Inputs: HLG, HDR10(PQ) Outputs: HLG, HDR10(PQ), Dolby Vision
- AWS Elemental MediaLive Inputs: HLG and HDR10(PQ) Outputs: HLG (Passthrough), HDR10(PQ)
Conclusion
In this three-part series, we explored the AWS tools and services used to integrate HDR support into your OTT video workflows. Implementing HDR can significantly enhance viewer experience and elevate your content, though it requires careful planning to ensure that colors are displayed as intended. Utilizing 10-bit video and having both HDR and SDR monitors are essential for achieving an outstanding end result. For further insights into career advancement, consider checking out this resource on how to ask for a raise.