[FFmpeg-devel] [PATCH] E-AC-3 spectral extension (bump)

[Michael Niedermayer]

On Thu, Mar 25, 2010 at 03:52:31PM +0100, Christophe Gisquet wrote:
> 2010/3/24 Michael Niedermayer <michaelni at gmx.at>:
> > would we overall have fewer unaligned accesses if we would place the array
> > so that not element 0 but element 1 is aligned?
> 
> I've just now see that this might be troublesome later on, as
> int32_to_float_fmul_scalar and ff_imdct_half are used on those buffers
> and both expect 16-bytes aligned data (movaps used).
> 
> >> num_copy_sections can definitely be >1. ?That is the whole point of it.
> >
> > if num_copy_sections is only rarely >1 than this optimization is maybe
> > not worth it
> 
> At least the samples on mplayerhq and the French TNT-HD broadcasts are
> in this situation.
> 
> Last but not least, I've used START/STOP_TIMER and oprofile to cycle
> counts and % of execution time. It appears that the CSI samples have
> CRC whose computation eats most of the runtime. Here are those figures
> as food for thought:
> 
>       | (1) | (2) |  (3) |  (4)  |  (5)  |  (6) |
> rambo | 1.0 |  64 | 3870 | 14000 |  11.2 |  0.0 | 11.2
> CSI   | 5.1 | 256 | 5020 | 83000 |   0.9 | 81.4 |  5.1
> CSI   | 2.0 | 128 | 1920 | 12700 |   0.3 | 81.1 |  1.6

i dont belive that crc calculation takes 80% of the time,
if it really does this is a bug
please make sure this percetage does not inlcude once run table init
on a very short file.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Observe your enemies, for they first find out your faults. -- Antisthenes
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