Video Technical Specifications

ScreenKey is designed to support professional video workflows while providing reliable playback across web, mobile, and TV devices.

When a video is uploaded to ScreenKey, we preserve the original uploaded file and create separate web-friendly streaming versions for playback.

You do not need to encode your video specifically for ScreenKey before uploading it. Our video processing pipeline automatically prepares uploaded media for streaming. However, files that already closely match our recommended encoding specifications may process significantly faster.

Original Files vs. Streaming Versions

Original File

The file originally uploaded to ScreenKey is preserved without modification for long-term storage.

When an authorized user downloads the original video, they receive the original uploaded file, including its original video, audio, and container configuration.

ScreenKey's streaming optimization does not modify or replace the source file.

Streaming Versions

When a user watches a video within ScreenKey, they do not stream the original uploaded file.

Instead, ScreenKey creates separate versions optimized for internet-based playback.

This is particularly important for professional video workflows, where source files can be hundreds of gigabytes in size or use codecs and bitrates that are not practical for playback in a web browser or consumer device.

For example, a 200 GiB production master can remain securely stored in its original format while ScreenKey delivers much smaller, optimized versions when someone streams the video.

Recommended Upload Encoding

ScreenKey will automatically convert uploaded videos into the formats required for streaming. However, if your video already closely matches the following configuration, ScreenKey may be able to process it more quickly.

Video

• Codec: H.264 / AVC
• Pixel format: YUV 4:2:0 (yuv420p)
• Color primaries: BT.709
• Transfer characteristics: BT.709
• Color matrix: BT.709
• Color range: Limited / TV range
• Maximum resolution: 1080p
• Video bitrate: Less than 16 Mbps

Audio

• Codec: AAC
• MPEG-4 Audio OTI
• Supported Audio Object Types:
  • AAC-LC (mp4a.40.2)
  • HE-AAC v1 (mp4a.40.5)
  • HE-AAC v2 (mp4a.40.29)

Container

• Container: ISO-BMFF-compliant MP4
• For optimal processing, the MP4 (moov) atom should preferably be located at the beginning of the file ("fast start").

Files that do not match these recommendations can still be uploaded. ScreenKey's video processing pipeline will create the necessary web-friendly versions automatically.

Streaming Technology

ScreenKey uses industry-standard adaptive streaming protocols:

• HLS (HTTP Live Streaming)
• MPEG-DASH

Streaming media is packaged using fragmented MP4 (fMP4) based on the ISO Base Media File Format (ISO-BMFF).

Rather than creating a single streaming file, ScreenKey generates multiple variants at different resolutions and bitrates. These variants allow the player to use Adaptive Bitrate Streaming (ABR) and select an appropriate quality based on the viewer's network conditions and playback environment.

Standard Streaming Specifications

For standard SDR playback, ScreenKey generates variants capped at 1080p, 720p, and 480p.

Video Configuration

• Codec: H.264 / AVC
• Pixel format: YUV 4:2:0 (yuv420p)
• Color primaries: BT.709
• Transfer characteristics: BT.709
• Color matrix: BT.709
• Color range: Limited / TV range

Audio Configuration

Streaming audio uses AAC with MPEG-4 Audio OTI.

Supported Audio Object Types include:

• AAC-LC (mp4a.40.2)
• HE-AAC v1 (mp4a.40.5)
• HE-AAC v2 (mp4a.40.29)

ScreenKey uses AAC-LC by default when audio needs to be transcoded. Compatible High-Efficiency AAC streams may be retained rather than unnecessarily transcoded.

Audio is prepared at different bitrate limits for each streaming quality:

• 1080p: Up to 256 Kbps
• 720p: Up to 128 Kbps
• 480p: Up to 96 Kbps

Adaptive Bitrate Playback

During playback, ScreenKey can dynamically select between the available streaming variants.

1080p → 720p → 480p

This allows playback quality to adjust based on available bandwidth and helps reduce buffering when network conditions change.

The original uploaded video's bitrate does not determine the amount of bandwidth required to stream it from ScreenKey. A high-bitrate production master is converted into the standardized streaming variants before it is made available for playback.

High Bitrate (HBR) Streaming

Projects with the High Bitrate (HBR) feature enabled receive an additional higher-quality streaming variant.

The HBR variant follows the same general configuration as ScreenKey's standard SDR streams:

• H.264 / AVC
• YUV 4:2:0
• BT.709
• Limited / TV range
• fMP4

The standard 1080p, 720p, and 480p variants are also generated. This allows ScreenKey to provide higher-quality playback when bandwidth and device capabilities allow while retaining lower-bitrate variants for adaptive playback.

HDR Streaming

Projects with the HDR feature enabled can receive an additional HDR streaming variant when ScreenKey detects supported HDR characteristics in the uploaded source.

HDR playback uses H.265 / HEVC and a 10-bit video pipeline.

HDR Video Configuration

• Codec: H.265 / HEVC
• Pixel format: 10-bit YUV 4:2:0 (yuv420p10le)
• Color primaries: BT.2020
• Transfer characteristics: SMPTE ST 2084 (PQ)
• Color matrix: BT.2020 non-constant luminance (bt2020nc)
• Color range: Limited / TV range
• Maximum resolution: 1440p
• Maximum video bitrate: 15 Mbps

HDR media continues to use the same fMP4 container and compatible AAC audio configuration used by the standard streaming pipeline.

Standard SDR variants are also generated to provide playback options for devices and environments that do not support the HDR stream.

Audio Streams and Channel Layouts

ScreenKey preserves the audio stream structure provided in the uploaded video. This distinction is particularly important for professional, mezzanine, mastering, and post-production files.

For the best general playback experience, we recommend delivering a consumer-ready audio mix.

Recommended: 5.1 Surround

A video can contain a single six-channel audio stream representing a standard 5.1 mix.

This allows all six channels to be treated as a single audio presentation during playback.

Recommended: Stereo

For stereo playback, the video should contain a single two-channel stream with a standard left/right stereo layout.

This tells the player that the left and right channels belong to the same audio presentation and should be played together.

Multiple Audio Streams

Videos may contain multiple consumer-ready audio streams.

ScreenKey preserves these audio streams and makes supported streams available as playback options. Multiple streams can be useful for different mixes, languages, commentary tracks, or other alternate audio presentations.

Individual Mono Audio Streams

Professional video files sometimes contain multiple independent mono streams rather than a finished stereo or surround mix.

In a particular production workflow, the first stream might represent the intended left channel and the second stream the intended right channel. However, from the media itself, ScreenKey may only know that these are two independent mono streams.

Unless sufficient metadata is available to establish their intended relationship, ScreenKey does not automatically combine independent mono streams into a stereo or surround mix.

If two independent mono streams are uploaded, they may therefore appear as separate audio options during playback rather than being played simultaneously as a stereo pair.

Why doesn't ScreenKey automatically combine them?

Individual mono streams are commonly used in professional workflows for purposes such as channel isolation, testing, mastering, mixing, and other post-production processes.

Without reliable metadata identifying the intended channel order and relationship, automatically combining streams would require ScreenKey to make assumptions about the source media. Those assumptions could result in an incorrect audio presentation.

For this reason, ScreenKey preserves the provided audio structure by default.

When a video is intended for general viewing, we recommend providing either:

• A single 2-channel stereo stream, or
• A single 6-channel 5.1 stream

Specialized DL/DR Audio Workflow

ScreenKey can also support a specialized audio format through custom integrations.

In this workflow, we receive six mono audio streams representing the individual channels of a 5.1 mix, plus two additional mono audio streams representing the left and right channels of a stereo mix.

The stereo streams are identified through their channel_layout  metadata:

• Left: 1 channels (DL)
• Right: 1 channels (DR)

Because this metadata provides ScreenKey with an explicit indication of the intended left and right channels, we can safely construct a stereo presentation without making assumptions about channel mapping.

When ScreenKey detects this supported configuration, we generate a synthetic stereo audio stream using the DL and DR streams. The generated stereo stream is inserted as the first audio track for playback within ScreenKey.

The Original Audio Is Preserved

Creating this synthetic playback stream does not modify the original uploaded video.

All original audio streams remain intact. The synthetic stereo track exists only within the streaming media generated by ScreenKey. If an authorized user downloads the original video, they receive the original file with its original audio streams and channel configuration exactly as uploaded.

Downloading Video

The versions ScreenKey generates for streaming are separate from the original uploaded video.

When an authorized user chooses to download the original video from ScreenKey, they receive the original uploaded file.

For example, if a 200 GiB ProRes file is uploaded:

• The original 200 GiB ProRes file is preserved.
• ScreenKey generates separate web-friendly versions for streaming.
• Users watching the video within ScreenKey receive the optimized streaming versions.
• Users downloading the original video receive the original ProRes file.

This allows ScreenKey to optimize playback without compromising the original media stored on the platform.

Quick Reference: Recommended Upload Configuration

If your goal is to minimize the amount of processing required before a video becomes available for streaming, we recommend the following configuration: