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Opus audio data packets begin with a "table of contents" (TOC) sequence which defines the frame duration, audio bandwidth and coding mode of the packet, as well as describing how individual frames are packed into the data packet. [RFC 6716 Section 3.1]. Other types of data packets are used with Opus in various containers are designed to start with a sequence which is not a valid TOC. This simplifies sorting such data for muxing implementations and ensures they will be rejected by the decoder if they are accidentally passed as Opus audio data.

Below is a list of such alternate sequences, to avoid duplication.

List of invalid Opus audio data sequences

  • `Og` is used as a prefix for metadata headers in .opus files. [RFC 7845]
  • '??` an 11-bit sequence (not yet defined) is used to distinguish `opus_control_header` packets in MPEG-TS. OpusTS