#7 VobSub subpictures support

[Ivan Vecera]

Hi all, sorry for delay. Now I have a patch for gpac,
that allows import VobSub subtitles. This is private
extension of Nero Digital format.

Limitations:
- Only VobSub (.idx/.sub) format supported
- VobSub features such as align, scale, alpha... stored
in .idx file are not supported

[Ivan Vecera]

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Hi again,
you can download the prebuilt binary for win32 at:

http://www.cera.cz/gpac/mp4box.zip

[Kurtnoise]

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Hi Falco,

First of all, great stuff...This new feature is really great
for MP4Box.

I've made some tests with your compile but all my subtitles
are rendered in green during the playback (tested with
Gabest MP4 Splitter and Haali Splitter). In addition with
VLC, subs are not displayed.

Have you got an idea about that ?

Thanks anyway.

++
Kurtnoise

[bond]

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"This is private extension of Nero Digital format."

what does this mean? does this mean its not compliant with
nero digital? if so, it doesnt really make much sense
imho :(

[Nobody/Anonymous]

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"This is private extension of Nero Digital format."

The Nero Digital is based on MPEG4. It adds some
non-standardized features such as subpictures and chapters.

The better sense would be:
"This is Nero Digital private extension for MP4."

[Nobody/Anonymous]

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Hi Kurtnoise,
I did not try Gabest nor Haali splitters. I only tried the
Nero Digital ShowTime player. Could you provide me please
some streams.
Thanks

Falco

[Kurtnoise]

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You need vobsub files only or mp4 streams ?

[Ivan Vecera]

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I found that Gabest splitter has a bug. In MP4Splitter.cpp
there is the following sequence:
=====
BYTE y = (pal[i+1]-16)*255/219;
BYTE u = pal[i+2];
BYTE v = pal[i+3];
BYTE r = (BYTE)min(max(1.0*y + 1.4022*(u-128), 0), 255);
BYTE g = (BYTE)min(max(1.0*y - 0.3456*(u-128) -
0.7145*(v-128), 0), 255);
BYTE b = (BYTE)min(max(1.0*y + 1.7710*(v-128), 0) , 255);
=====

The subpictures palette in MP4 file is stored in decoder
specific info of the track and the content is:
0 1 2 3 4 5 6 7 60 61 62 63
0, Y1, V1, U1, 0, Y2, V2, U3, ..., 0, Y15, V15, U15

where Yn, Vn, Un is YUV representation of n color.
Gabest uses order 0, Y, U, V and this is first bug. The
second one is on line with green component.

The generic formula for conversion from YUV to RGB is:
R = Y + 1.403V
G = Y - 0.344U - 0.714V
B = Y + 1.770U

Gabest uses:
R = Y + 1.403U
G = Y - 0.344U - 0.714V
B = Y + 1.770V

Differences are on first and last lines. But because of
first bug (U & V components are swapped) the first and last
lines are correct. The problem is in second line because the
U and V components are swapped the coefficients 0.344 and
0.714 are applied on incorrectly so the green component of
RGB is not valid.

Falco

[Ivan Vecera]

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Hi all,
I found also bug in my color conversion in the patch. I have
updated the patch (see below).
The prebuilt version of patched mp4box is available:

http://www.cera.cz/gpac/mp4box-20060504.zip

Regards
Falco

[Kurtnoise]

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Hi Falco,

Could you provide the sources of your last build (20060505)
? Iwould like to compile MP4Box with vobsub support in my
Linux distro.

fyi : you can find vobsub sources here :
http://www.divx-digest.com/software/vobsub.html . For vobsub
extraction. Hope this help.

[Ivan Vecera]

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Hi all,
I'm sending latest patch to gpac.

- [FEATURE] - possibility to export VobSub track as single
track MP4 file and reimport into new MP4 file
- [FEATURE] - delay parameter from .idx file is now processed
- [BUGFIX] - problems with incorrect colors in Nero
ShowTime and MPC fixed

[Ivan Vecera]

VobSub subpictures support (latest patch version)

[Jean Le Feuvre]

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Many thanks for this great patch - I simply wouldn't have
had the time to look at it. VobSub has been integrated in
CVS now.