[vlc-devel] Fixes for HDTV grey line bug

[Marian Durkovic]

Hi all,

  in an attempt to fix the annoying HDTV grey line bug (caused by displaying
1088 lines instead of only 1080 real lines) I've found the following
changesets:

https://trac.videolan.org/vlc/changeset/10160
https://trac.videolan.org/vlc/changeset/10161

  Looking at the video output modules, seems only the ones which deliver 
more than 1 direct buffer are affected (namely xvideo and sdl, are there
others?). The modules which deliver only 1 direct buffer (e.g. directx)
and go through memcpy work fine, also indirect rendering works of course.

  For the mentioned ones, the fixes seem to be quite simple:

xvideo:
-------

make sure that the buffer width/height is aligned to a multiple of 16,
xvideo handles cropping automatically.

The following code solves the problem, it needs to be put into
modules/video_output/x11/xcommon.c, functions CreateShmImage() and 
CreateImage() - just under #ifdef MODULE_NAME_IS_xvideo

    /* Make sure the buffer is aligned to multiple of 16 */
    i_height = ( i_height + 15 ) >> 4 << 4;
    i_width = ( i_width + 15 ) >> 4 << 4;

sdl:
----

unfortunately sdl doesn't seem to be able of cropping the buffer, so the 
only solution seems to be reducing number of direct buffers to 1 in 
modules/video_output/sdl.c:

#define SDL_MAX_DIRECTBUFFERS 1

With the above changes, changeset 10160 could be reapplied, but it needs
to be enhanced with the following check, since some broadcasters ignore 
the MPEG2 spec:

    if( i_height == 1088 )
    {
        i_height = 1080;
        msg_Warn( p_vout, "Incorrect HDTV stream - reducing height to 1080");
    }


	With kind regards, 


		M.

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----   Marian Durkovic                       network  manager         ----
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