[mpeg2-dev] mmxext acceleration

[Gour <go...@go...>]

Hiya!

Everything started with crashes I experienced with dvdwizard which
lead us to transcode.

However, transcode dev says it's the problem with libmpeg2 lib.

What is the issue?

When invoking transcode I get the following:

> cmove asm decode_mpeg2.c  libmpeg2 acceleration: mmxext


which means that libmpeg2 says that mmxext instruction set can be uses, although my CPU (i7 860) does not support it, according to cpuinfo:

flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx
rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology
tsc_reliable nonstop_tsc pni dtes64 monitor ds_cpl vmx smx est tm2
ssse3 cx16 xtpr pdcm sse4_1 sse4_2 popcnt lahf_lm ida tpr_shadow vnmi
flexpriority ept vpid

Inspecting the libmpeg2 code I've found the following:

#if defined(ARCH_X86) || defined(ARCH_X86_64)
static inline uint32_t arch_accel (uint32_t accel)
{
    if (accel & (MPEG2_ACCEL_X86_3DNOW | MPEG2_ACCEL_X86_MMXEXT))
	accel |= MPEG2_ACCEL_X86_MMX;
	
    if (accel & (MPEG2_ACCEL_X86_SSE2 | MPEG2_ACCEL_X86_SSE3))
	accel |= MPEG2_ACCEL_X86_MMXEXT;
	
    if (accel & (MPEG2_ACCEL_X86_SSE3))
	accel |= MPEG2_ACCEL_X86_SSE2;

in cpu_accel.c which, if I read C correctly means, that libmpeg2 sets
MMXEXT set if the following is true: 

(MPEG2_ACCEL_X86_SSE2 | MPEG2_ACCEL_X86_SSE3) 

which is not the case with my cpu having support for SSE2, but not MMXEXT.

Am I right, or something else is going on that libmpeg2 sends 'wrong'
info about acceleration to the transcode?


Sincerely,
Gour

-- 

Gour  | Hlapicina, Croatia  | GPG key: F96FF5F6
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