 beginning and may contain them in part at the end, as
        long as not physically removed yet at the beginning and/or the end.

    3.5 priming samples
        padded samples at the beginning of the Opus bitstream

    3.6 sample-accurate
        for any PCM sample, a timestamp exactly matching its sampling timestamp is present in the media timeline.

    3.7 valid samples
        PCM samples after decoding Opus sample(s) corresponding to input PCM samples

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4 Design Rules of Encapsulati