[FFmpeg-devel] [PATCH 1/4] mxfenc: explicitly truncate continuity count.

Tomas Härdin tomas.hardin at codemill.se
Mon Oct 15 17:59:27 CEST 2012

On Mon, 2012-10-15 at 16:07 +0200, Michael Niedermayer wrote:
> The field is intended to overflow and have only its low 16bits stored.
> This commit avoids the implicit truncation and clarifies that its
> intended and not a bug
> Approved-by: Tjoppen

For completeness and posterity I'll quote the relevant spec, S326m
section 7.6 ("Continuity count"):

> The continuity count word consists of 2 bytes allow-
> ing a number to be created by a modulo 65536
> counter (bits C15 to C0 in figure 7). The continuity
> count shall increment by 1 for each newly transmit-
> ted content package with the same SDTI source and
> destination addresses. The continuity count may
> be used to detect whether the content package
> sequence has been broken by an operation such as
> a routing switch.

IIRC MPEG-TS has something similar, except the counter is 4-bit instead
of 16-bit.


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