Re: [libdv-dev] libdv encode on IA64

[Brent C. <bca...@sg...>]

I seem to have found the problem, though I'm short on time and
unable to look into the root cause at the moment.

The issue is in reorder_block(), where the zigzag is performed.
I noticed in the !ARCH_X86 && !ARCH_X86_64 code path that there
were the following two lines:

	  //		*(unsigned short*) ((char*) zigzag + reorder[i])=bl->coeffs[i];
	  zigzag[reorder[i] - 1] = bl->coeffs[i];

When I uncomment the first and comment the second, the output
is no longer corrupted.  Granted, the code as-is looks more correct,
but obviously it's producing incorrect results. *boggle*

If I don't hear from anyone I'll look closer into this next week.

Brent

On Thu, 2 Mar 2006, Brent Casavant wrote:

> Have any of you run the libdv encoder (via encodedv, or otherwise) on IA64?
> I find that the output of the encoder is incorrect, despite correct
> input.  To be clear, the decoder seems to generate correct results.
> 
> As an example, I ran a 720x480 ppm image through encodedv both on i386
> and IA64.  The i386 DV file played back correctly, the IA64 DV file
> was corrupted.  I've managed to narrow the problem down to
> dv_encode_full_frame() -- identical input on both platforms produces
> different output.
> 
> This is with pristine libdv-0.104 code, FWIW.
> 
> Also, has there been any work done on adding SIMD instruction support
> for IA64?  Last fall I implemenented the brute-force idct_88() code
> using IA64 SIMD, and while it was indeed much faster, it wasn't
> fast enough for realtime playback.  If someone could describe the
> algorithm used in the x86 MMX routines, I could probably put together
> an equivalent IA64 SIMD version.
> 
> Thank you,
> Brent Casavant
> 
> -- 
> Brent Casavant                          All music is folk music.  I ain't
> bca...@sg...                        never heard a horse sing a song.
> Silicon Graphics, Inc.                    -- Louis Armstrong
> 
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-- 
Brent Casavant                          All music is folk music.  I ain't
bca...@sg...                        never heard a horse sing a song.
Silicon Graphics, Inc.                    -- Louis Armstrong