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What is an IDR Frame?

An instantaneous decoding refresh (IDR) frame is an intra-coded picture in H.264 or H.265 video. Pictures decoded after it cannot reference any picture that precedes it, providing a clean point for decoder refresh.

How IDR Frames work

An IDR picture is a coded access point that resets inter-picture reference history for subsequent H.264 or HEVC decoding. Its slices use intra prediction, and following pictures in the coded sequence are barred from depending on pictures that came before the refresh. This is stronger than merely inserting an intra-coded picture. Encoders place IDRs where independent startup, segment boundaries, channel changes, or deterministic error recovery are required.

Key facts

  1. Every IDR picture is intra-coded, but an ordinary I-picture need not clear the reference buffer; seeking to a non-IDR I-picture can therefore leave later frames dependent on unavailable history.
  2. An IDR normally begins a new coded video sequence for random access, but containers and manifests must expose that access point correctly or players may still start on a non-decodable sample.
  3. Forcing frequent IDRs interrupts long-range temporal prediction and adds large intra pictures, increasing bitrate or reducing quality under a fixed bitrate even though access and recovery improve.

When IDR Frames matter

Place IDR frames at segment boundaries when viewers must begin decoding or switch renditions without earlier frame data. More frequent IDR frames improve seeking and recovery but generally reduce compression efficiency.

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