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What is RTMP Pass-Through?

RTMP pass-through relays an incoming Real-Time Messaging Protocol stream to another endpoint while preserving its encoded media. Unlike transcoding, it does not decode and recompress the audio or video.

How RTMP Pass-Through works

In pass-through mode, a service receives RTMP messages, preserves the compressed tracks, and republishes them toward another RTMP endpoint. It may still demultiplex, remultiplex, adjust timestamps, or reconnect the session, so relay behavior is not necessarily a byte-for-byte copy. Avoiding codec reconstruction reduces compute demand and prevents generational quality loss. The relay sits in the live ingest path when source encoding already satisfies the destination’s codec, rate, and packaging expectations.

Key facts

  1. Classic RTMP commonly carries H.264 video and AAC audio in FLV-style messages, making that combination a frequent compatibility baseline for pass-through ingest.
  2. A relay cannot repair an unsupported codec, excessive bitrate, invalid keyframe cadence, or mismatched audio layout without transforming the media or rejecting it.
  3. Timestamp discontinuities and source reconnects can propagate downstream; a robust relay must decide whether to preserve, normalize, or restart the outgoing timeline.

When RTMP Pass-Through matters

Use pass-through to restream a compatible live feed with low processing overhead and no re-encoding loss. The destination must accept the original codecs and stream parameters, or playback or ingestion may fail.

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