[XviD-devel] xvid_bench (crc fixes)

Paul Kurucz ptk9417 at ritvax.isc.rit.edu
Wed Jun 22 14:31:36 CEST 2005


On Wed, 15 Jun 2005 17:56:48 +0200
Christoph Nägeli <chn at kbw.ch> wrote:

> >> Works as expected.  The only notable difference:
> >>
> >>     Linux:
> >>         ALTIVEC - dequant_mpeg_inter 19.005 usec        
> >> crc32=0xa194919e | ERROR
> >>     OSX:
> >>         ALTIVEC - dequant_mpeg_inter 12.138 usec        
> >> crc32=0xd878c722

> Especially since dequant_mpeg routines are NOT tested on linux due to  
> the fact that noone
> was responding when I looked for a person testing that altivec stuff  
> on linux...

Just as a heads-up.  The problem appears to be rounding/lsb related, only occuring in the highest frequency bin, performing a dequant on 187(which is outside of the normal -127 to 127 range).  I haven't tracked down the cause.  But I don't see this as causing a problem because all of the inputs to the dequant should be in the "normal" range.

Quick debug output:
...
ERROR : dequant_mpeg_inter i:63 qm:1 quant:1 input:187 C_result:22 ASM_result:23
ERROR : dequant_mpeg_inter i:63 qm:1 quant:7 input:187 C_result:165 ASM_result:164
ERROR : dequant_mpeg_inter i:63 qm:1 quant:9 input:187 C_result:211 ASM_result:210
ERROR : dequant_mpeg_inter i:63 qm:1 quant:15 input:187 C_result:350 ASM_result:351
ERROR : dequant_mpeg_inter i:63 qm:1 quant:17 input:187 C_result:399 ASM_result:398
ERROR : dequant_mpeg_inter i:63 qm:1 quant:23 input:187 C_result:538 ASM_result:539
ERROR : dequant_mpeg_inter i:63 qm:1 quant:25 input:187 C_result:584 ASM_result:585
ERROR : dequant_mpeg_inter i:63 qm:1 quant:31 input:187 C_result:727 ASM_result:726
ERROR : dequant_mpeg_inter i:63 qm:3 quant:3 input:187 C_result:211 ASM_result:210
ERROR : dequant_mpeg_inter i:63 qm:3 quant:5 input:187 C_result:350 ASM_result:351
ERROR : dequant_mpeg_inter i:63 qm:3 quant:11 input:187 C_result:772 ASM_result:773
...
ERROR : dequant_mpeg_inter i:63 qm:54 quant:9 input:187 C_result:2046 ASM_result:2047
ERROR : dequant_mpeg_inter i:63 qm:54 quant:10 input:187 C_result:2047 ASM_result:2046
ERROR : dequant_mpeg_inter i:63 qm:54 quant:13 input:187 C_result:2046 ASM_result:2047
ERROR : dequant_mpeg_inter i:63 qm:55 quant:1 input:187 C_result:1288 ASM_result:1289
ERROR : dequant_mpeg_inter i:63 qm:55 quant:2 input:187 C_result:2046 ASM_result:2047
ERROR : dequant_mpeg_inter i:63 qm:55 quant:3 input:187 C_result:2047 ASM_result:2046
ERROR : dequant_mpeg_inter i:63 qm:55 quant:4 input:187 C_result:2047 ASM_result:2046
ERROR : dequant_mpeg_inter i:63 qm:55 quant:10 input:187 C_result:2046 ASM_result:2047
ERROR : dequant_mpeg_inter i:63 qm:55 quant:12 input:187 C_result:2046 ASM_result:2047
ERROR : dequant_mpeg_inter i:63 qm:56 quant:13 input:187 C_result:2047 ASM_result:2046
ERROR : dequant_mpeg_inter i:63 qm:57 quant:1 input:187 C_result:1334 ASM_result:1335
ERROR : dequant_mpeg_inter i:63 qm:57 quant:2 input:187 C_result:2046 ASM_result:2047
...

i:63 is the 64th frequency bin (Dst[63]).
qm:  The value that the quant matrix is initialized to.. via set_inter_matrix

Paul 


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