HLS2SRT / Contribution Gateway
SOURCE REVIEWED C++ IMPLEMENTATIONHLS2SRT selects HLS services, remuxes their elementary streams into MPEG-TS and delivers SPTS or MPTS over SRT and UDP—without forcing a decode and re-encode cycle.
Resolution, codec and bitrate come from the selected HLS input. Use the CDN++ transcoding fabric when a new adaptive-bitrate ladder is required.
End-to-end remux path
The source code establishes a clean contribution boundary: inspect the adaptive input, choose deliberately, normalize it for MPEG-TS and hand the result to the required network protocol.
Read media or master playlists, inspect the available streams and identify the video, audio and program context that should enter the contribution path.
MASTER · VARIANT · MEDIAChoose the required program and audio language instead of carrying every rendition or track by accident.
PROGRAM · AUDIO · LANGUAGEMap the selected elementary streams into MPEG-TS and apply H.264 or HEVC Annex-B bitstream conversion when the source requires it.
NO RE-ENCODEOperate SRT in caller or listener mode, or use managed UDP destinations including unicast and multicast network paths.
SRT · UDPUse producer queues, a dedicated writer and explicit reconnect behavior to keep input work separated from the output transport.
BOUNDED QUEUE · RECONNECTUseful for contribution handoff, protocol conversion and operational fan-out.
Useful when independent inputs need a shared MPEG-TS contribution multiplex.
Four implementations in one code family
The supplied project contains several executable directions. They share the same media idea but target different operational roles.
A Dear ImGui, OpenGL and SDL2 application plays the selected HLS feed locally while optionally remuxing the same packets to an SRT destination.
A compact service converts one HLS input into MPEG-TS and writes it to one or more SRT or UDP destinations without a decoding and encoding cycle.
Multiple HLS sources become separate MPEG-TS programs inside one multiplex, with program metadata, paced packet writing and reconnection logic.
Experimental variants extend the multiplex toward simultaneous SRT clients and a local segmented-HLS output. They demonstrate direction, not finished production scale.
What the supplied code establishes
These capabilities come directly from the attached C++ sources. Prototype branches are identified separately from the reviewed core.
libavformat, libavcodec and libavutil handle stream inspection, packet mapping, bitstream filters, timestamp rescaling and MPEG-TS output.
C++23 · LIBAVFORMAT · LIBAVCODECThe same remux path can feed SRT or UDP destinations, keeping transport policy separate from codec and program selection.
SRT CALLER / LISTENER · UDPThe code supports one selected service as SPTS and aggregates independent sources as programs inside an MPTS.
SPTS · MPTS · AVPROGRAMPer-program producers, bounded queues and a dedicated writer provide a practical base for isolating ingest timing from multiplex output.
PRODUCERS · QUEUE · WRITERH.264 and HEVC streams may be converted to Annex-B framing for MPEG-TS compatibility, but their encoded picture content remains unchanged. There is no hidden quality ladder, resolution change or bitrate reduction inside HLS2SRT.
Production boundary
The supplied implementations prove the transport architecture. The next engineering phase turns that proof into a secure, observable and supportable 24×7 gateway.
Normalize PTS, DTS and PCR across independent HLS timelines and discontinuities
Isolate destination backpressure so one slow output cannot stall every client
Externalize program, audio-language, URL and transport policy into validated configuration
Add SRT passphrase, stream ID, access policy and secret-management boundaries
Expose bitrate, queue depth, packet age, reconnect and loss/retransmission metrics
Define bounded drop, restart and recovery behavior for 24×7 unattended operation
HLS2SRT + CDN++
HLS2SRT brings existing adaptive HTTP streams into a managed MPEG-TS contribution path. CDN++ can then separate programs, build GPU or CPU ABR ladders, package HLS and apply origin and delivery policy.
Open the CDN++ processing architectureSPICA Networks engineering
