[Matroska-users] "ERR0B1: SimpleBlock at 5979 track #2 is not a keyframe" error thrown by mkvalidator tool

Moritz Bunkus moritz at bunkus.org
Tue Feb 13 17:01:05 CET 2018


> Indeed, the audio frame are not marked as keyframe. That is incorrect
> for audio tracks (unless some codec has some special requirement, but
> that's currently not the case).

Uhm, in general you're not entirely correct. I know of at least two audio
codecs that actually do differentiate between key and non-key frames: one
of the older RealAudio variants and the very-much-current TrueHD. TrueHD
calls them "sync frames" vs "normal frames". Only "sync frames" contain
full headers, and decoders can only start decoding from "sync frames" but
not from "normal" ones. Hence, "sync frames" are flagged as key frames
whereas "normal" ones aren't.

Opus doesn't belong to that category, true, but mkvalidator must not assume
that all audio frames have to be marked as key frames.

That file has a totally different problem, though: the audio track doesn't
have a CodecPrivate element… Therefore its data cannot be decoded. mkvmerge
does therefore not recognize the track, and even trying to ffmpeg to decode
it fails (VLC produces… something awful, too).

Kind regards,

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