Video Linux SDK Release Notes

Added

• Client Observability: quality restriction insights. Statistics now provide more detail on why video quality is being limited, for both subscribers and publishers:

  • Subscriber video statistics now report whether the received video quality is being restricted, and where the restriction originates. The new sender_quality_restriction field of otc_subscriber_video_stats reflects restrictions applied by the immediate sender (the Media Router in routed sessions, or the publisher in relayed sessions).
  • The new remote_publisher_quality_restriction field reflects restrictions applied by the originating publisher, such as CPU or uplink bandwidth constraints.
  • Changes in the sender quality restriction are now also reported as a reason in the subscriber on_video_quality_changed callback.
  • The network condition reason now includes two new values, which apply only to the publisher's transport: OTC_NETWORK_REASON_NO_SUBSCRIBERS (the publisher bitrate is limited because there are no active subscribers) and OTC_NETWORK_REASON_DOWNSTREAM_CONSTRAINT (the publisher bitrate is constrained by downstream receiver conditions, typically when client simulcast is disabled).

  For more information, see this documentation.

• This version includes an update to the bundled CA certificates used by the SDK for establishing secure connections. This file contains trusted Certificate Authority certificates that the SDK uses to verify SSL/TLS connections, ensuring secure communication with external services. This file serves as a fallback and is only used when the SDK cannot locate a CA certificate bundle in the system. This routine update adds newly trusted CAs and removes outdated certificates.

• End-to-end encryption: new error when encryption is not enabled. Setting an encryption secret in a session that was not created with end-to-end encryption enabled now results in a new encryption not enabled error (OTC_SESSION_ENCRYPTION_NOT_ENABLED, OTC_PUBLISHER_ENCRYPTION_NOT_ENABLED, or OTC_SUBSCRIBER_ENCRYPTION_NOT_ENABLED). Previously, the secret was silently ignored. For more information, see this documentation.

• This version updates the root certificates embedded in the WebRTC library used by the SDK, so that certificates issued by the compromised eMudhra (emSign) intermediate certificate authorities are no longer trusted. WebRTC uses these root certificates to verify secure connections to TURN servers over TLS. In October 2026, the private keys of eight eMudhra intermediate certificate authorities were found to be recoverable, which could allow trusted-looking certificates to be created for any domain. For more information about the incident, see this Cloudflare article.

Added

• This version adds a new API that allows publishers to explicitly set the target scalability mode, giving developers fine-grained control over the number of spatial (resolution) and temporal (frame rate) layers used during encoding. This enables applications to better balance video quality, adaptability, and resource usage based on their specific needs. For more information, see this documentation. This is a beta feature.

• This version of the SDK now uses WebRTC M145, a recent milestone from Google's WebRTC library. The upgrade brings improvements in performance, stability, and security across all supported native platforms. It includes bug fixes and performance enhancements to audio and video media codecs, better network adaptation, and improved compatibility with modern platform environments. This update ensures the SDK remains aligned with the current WebRTC specification and maintains a strong foundation for future feature development. As a result of this upgrade, version 2.35.1+ of the SDK only supports systems with GLIBC 2.38 or higher on arm7 and arm64 architectures.

• This version includes an update to the bundled CA certificates used by the SDK for establishing secure connections. This file contains trusted Certificate Authority certificates that the SDK uses to verify SSL/TLS connections, ensuring secure communication with external services. This file serves as a fallback and is only used when the SDK cannot locate a CA certificate bundle in the system. This routine update adds newly trusted CAs and removes outdated certificates.

• The otc_video_frame_set_metadata() and otc_video_frame_get_metadata() functions, deprecated in 2.33.0, have been removed in this version.

Fixed

• Fixed an issue where calling otc_session_publish() inside the on_session_connected callback could fail due to a race condition caused by the session's internal connected state not being updated before the callback fired.

Fixed

• Fixed an issue where a publisher's video stream was lost after an Adaptive Media Routing (AMR) transition to a routed topology, following a specific sequence of mute/unmute operations and subscriber joins.

• This version adds new network condition metrics to the client observability feature, providing detailed visibility into network performance and quality indicators. These metrics complement the publisher and subscriber statistics introduced in 2.33.0 and help developers proactively monitor network conditions affecting video quality, diagnose connectivity issues, and make informed decisions about potential adjustments. For more information, see this documentation.

• This version adds support for Live Captions Translation, which provides real-time subtitle translation during video calls. Each participant can independently select their preferred translation language. This feature supports the full AWS Translate language set. This is a Private Beta feature—to enable Live Captions Translation for your project, contact us. For more information about Live Captions, see this documentation.

• This version adds new publisher and subscriber statistics including: video layer metrics for simulcast/SVC and transport statistics for publishers; video freeze/pause tracking and decoding metrics for subscribers; and video quality changed events for both publishers and subscribers. For more information, see this documentation.

• This version adds full support for network statistics of senders for subscribers in video sessions (which was previously in beta). For more information, see this documentation.

• This version adds publisher degradation preference settings to control how video quality adapts when bandwidth or CPU resources are limited. For more information, see this documentation.

• This version adds support for Debian 13 and removes support for Debian 12.

• This version includes an update to the bundled CA certificates used by the SDK for establishing secure connections. This file contains trusted Certificate Authority certificates that the SDK uses to verify SSL/TLS connections, ensuring secure communication with external services. This file serves as a fallback and is only used when the SDK cannot locate a CA certificate bundle in the system. This routine update adds newly trusted CAs and removes outdated certificates. Note: While we regularly update this certificate bundle, this is the first time we're explicitly documenting it in our release notes for transparency.

• In this version we are deprecating the otc_video_frame_set_metadata() and otc_video_frame_get_metadata() functions. These functions will be removed in future minor releases.