Re: Assertion failed : p >= thisvob->vobu[i - 1].sectpts[1], file dvdvob.c, line 1881

On Mon, 24 Dec 2012 11:05:00 +0100, Jean-Pierre Planas wrote:

> STAT: VOBU 1680 at 477MB, 8 PGCs
>  STAT: VOBU 1696 at 482MB, 8 PGCs
>  WARN: Cannot detect pts for VOBU if there is no audio or video
>  WARN: Using SCR instead.
>  Assertion failed: p >= thisvob->vobu[i - 1].sectpts[1], file
> dvdvob.c, line 1881

Thanks to Jean-Pierre for providing the sample file that triggered this
error. I have investigated it, and determined it terminates with a
truncated VOBU, consisting of just a NAV pack and nothing else. The
last part of an mpeg2desc dump looks like this:

032e7000: mpeg2 pack hdr, 94.653 sec
032e700e: system header; length=18
032e7026: pes private2, PCI; length=980
032e7400: pes private2, DSI; length=1018

In short, this is a malformed input file. It can be very easily
converted to a valid file, by passing it through FFmpeg, e.g.:

ffmpeg -i <input-file> -target pal-dvd -acodec copy -vcodec copy <output-file>

The above assertion failure arises from dvdauthor trying to guess at a
value for the missing time in the nonexistent VOBU contents, and coming
up with an inconsistent answer. I have changed the code to display more
information, including the offset of the offending sector within the
input file at which such problems are found. The output from dvdauthor
now looks like this:

STAT: Processing VTS_08_1.VOB...
WARN: Cannot detect pts for VOBU at inoffset 0x32e7800 if there is no audio or video
WARN: Using SCR instead.
ERR:  pts 8519384 rounded up to 8522824 at rate 3600 lies within previous vobu 196 [8486824..8530024] at inoffset 0x32e7800

Those “inoffset” values should at least narrow down the part of the
file to look at to discover the source of the error.

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