[FFmpeg-devel] [PATCH] read palette information from extradata for dvd subtitle decoder

[elupus]

elupus <elupus <at> ecce.se> writes:

> 
> Ian Caulfield <ian.caulfield <at> gmail.com> writes:
> 
--
> > When Nero Digital shoves dvd subtitles into mp4 files, it seems to
> > include the (binary) palette data from the IFO as extradata...
> > 
> > Ian
> > 
> 
>   uint32_t palette[16]; /* New type struct {zero_1, Y, Cr, Cb} ? */
> 
> As taken from the PGC ifo struct. So just the 16 32bit values? Need some 
good 
> way to tell them apart reliably then, any ideas?
> 


Found these tidbits from gpac muxer for mp4

> 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

Odd order of the yuv components. Probably a result of gabest nice old vobsub 
bug that is also mentioned.

> 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

U and V are swapped on first and last line.