[xine-devel] VLD XvMC extension and support in xine.

[<uni...@sh...>]

Hi, all!

I'm new to this list but I am having discussions with Andreas Robinson=20
who made a post concerning "Hardware decoding and Xine" lib, about the=20
way to go to implement VIA's HW mpeg decoders in xine. I have no=20
connection whatsoever with VIA.

The VIA decoders cannot do  XvMC "MOCOMP" and "IDCT" levels of HW=20
decoding. Therefore the "unichrome" sourceforge project made a=20
nonstandard  extension to XvMC which we named "VLD", (variable length=20
decoding) which basically takes care of all decoding. However, according=20
to Mark Vojkovic, the "father" of XvMC,  there is no chance that this=20
level will be standard until another HW developer agrees on an API.=20
Anyway, the API is implemented and working using DRI.

Now, in order to implement Xine support for this level of XvMC in=20
"video_out_xvmc" and also to help Andreas easily make some sort of =20
"video_out_viadirectfb" plugin out of the video_out_xvmc plugin, an idea=20
is to add the following methods to "video_out.h", "struct vo_frame_s"


   /* XvMC methods for VLD acceleration */
   void (*proc_vld_frame) (struct vo_frame_s *this_gen,
               const vo_vld_frame_t *vft,
               vo_frame_t *current_frame,
               vo_frame_t *forward_ref_frame,
               vo_frame_t *backward_ref_frame);

   void (*proc_vld_slice) (struct vo_frame_s *this_gen,
               const uint8_t *slice,
               int num_bytes);

"proc_vld_frame" is called before decoding of a frame and=20
"proc_vld_frame" is called to send each slice to the output plugin. The=20
decoder plugin must determine when the last slice of a frame is sent.

The vo_vld_frame_t contains at least (for mpeg2 and mpeg1)

typedef struct vo_vld_frame_s {
   int vld_frame_t_version;  /* For future backward binary compatibility =
*/
   int mv_ranges[2][2];  =20
   int picture_structure;
   int intra_dc_precision;
   int mpeg_coding; /* 1, 2, 4 etc.*/
   int progressive_sequence;
   int scan;
   int pred_dct_frame;
   int concealment_motion_vectors;
   int q_scale_type;
   int intra_vlc_format;
   int second_field;
   int load_intra_quantizer_matrix;
   int load_non_intra_quantizer_matrix;
   uint8_t intra_quantizer_matrix[64];
   uint8_t non_intra_quantizer_matrix[64];
    ...
    ...
    ...
    ...
} vo_vld_frame_t;

and probably needs to be extended for a) mpeg4 support, b) if a standard=20
VLD XvMC API is agreed upon.

Knowing that this will break backward binary compatibility of libxine=20
I'm asking for your advice if the change is at all feasible. It would=20
probably make the life much easier for me, Andreas and future=20
implementors of mpeg4 etc.

Any answer would be greatly appreciated.

Best regards
Thomas Hellstr=F6m