[libdvdnav-devel] IFO header parser bug?

[Lawrence D'Oliveiro]

On Sat, 9 May 2020 17:53:56 -0700, David Ehrmann wrote:

> I was authoring a DVD and ran across a discrepancy between the
> behavior of dvdauthor and libdvdread. read_video_attr() reads the
> second byte of video attributes as follows:
> 
> va->line21_cc_1 = dvdread_getbits(&state, 1);
> va->line21_cc_2 = dvdread_getbits(&state, 1);
> va->unknown1 = dvdread_getbits(&state, 1);
> va->bit_rate = dvdread_getbits(&state, 1);
> va->picture_size = dvdread_getbits(&state, 2);
> va->letterboxed = dvdread_getbits(&state, 1);
> va->film_mode = dvdread_getbits(&state, 1);
> 
> The first two CC bits and the last film bit agree with the doc I
> found, but the resolution and letterboxed bits don't. See
> http://dvd.sourceforge.net/dvdinfo/ifo.html

The version I’ve been using is <http://www.mpucoder.com/DVD/ifo.html>,
which seems to have slightly more detail than the above version (but
otherwise agrees with it).

I started this wikibook
<https://en.wikibooks.org/wiki/Inside_DVD-Video> a while back, trying
to document everything that wasn’t (I thought) adequately explained
elsewhere.