[Mplayer-users] mpeg 16bpp bug - HELP US

Arpi arpi at thot.banki.hu
Sun May 6 04:12:19 CEST 2001


> This bug appears only in 16bpp X11 output. At least at my machine
SDL has its own YV12->RGB converter, and Xv doesn't require it.
So only X11, DGA, SVGA and fbdev uses it.

I spent some time reading that MMX code (i don't know much about MMX)
and found 3 possible reason:

1. bad compiler  - can you please send me your binary (with MMX enabled)?
   i'll try it, if it fails here then problem is in your gcc/as
   (gcc 2.96 is known to be buggy, and your ld version is also strange,
   I have 2.9.1 here...)
2. unsupported MMX instructions - i've seen that movq/movntq is used to
   store results, if they fail, no image at all. so it's possible too.
   i hope that Nick or other MMX guru will help me in this.
3. data alignment. there are some comments about constants must be 8-byte
   aligned. but there are no special things to ensure this. btw I think
   that it must work without the alignment too, but slower. Nick?

1. and 3. should be decided when I try your binary. 2. should be shooted,
because i got such reports from dual P3 too.

Also, I've found that MMX is not used for 15bpp. SO 15bpp is always C,
this way it works.
(I remembered that 15 and 16 bpp code is the same, and only tables differ.
it's true for C version, but MMX version doesn't use tables)

A'rpi / Astral & ESP-team

mailto:arpi at thot.banki.hu

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