mirror of https://git.ffmpeg.org/ffmpeg.git
spelling/grammar/wording/phrasing
Originally committed as revision 4376 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Diego Biurrun
parent
38aca76027
commit
8ea9ce413b
|
|
@ -1,102 +1,104 @@
|
|||
optimization Tips (for libavcodec):
|
||||
|
||||
What to optimize:
|
||||
if you plan to do non-x86 architecture specific optimiztions (SIMD normally) then
|
||||
take a look in the i386/ directory, as most important functions are allready
|
||||
optimized for MMX
|
||||
If you plan to do non-x86 architecture specific optimiztions (SIMD normally)
|
||||
then take a look in the i386/ directory, as most important functions are
|
||||
already optimized for MMX.
|
||||
|
||||
if you want to do x86 optimizations then u can either try to finetune the stuff in the
|
||||
i386 directory or find some other functions in the c source to optimize, but there
|
||||
arent many left
|
||||
If you want to do x86 optimizations then you can either try to finetune the
|
||||
stuff in the i386 directory or find some other functions in the C source to
|
||||
optimize, but there aren't many left.
|
||||
|
||||
Understanding these overoptimized functions:
|
||||
as many functions, like the c ones tend to be a bit unreadable currently becouse
|
||||
of optimizations it is difficult to understand them (and write arichtecture
|
||||
specific versions, or optimize the c functions further) it is recommanded to look
|
||||
at older CVS versions of the interresting files (just use CVSWEB at
|
||||
http://www1.mplayerhq.hu/cgi-bin/cvsweb.cgi/ffmpeg/libavcodec/?cvsroot=FFmpeg)
|
||||
or perhaps look into the other architecture specific versions in i386/, ppc/,
|
||||
alpha/, ...; even if u dont understand the instructions exactly it could help
|
||||
understanding the functions & how they can be optimized
|
||||
As many functions, like the C ones tend to be a bit unreadable currently
|
||||
because of optimizations it is difficult to understand them (and write
|
||||
architecture specific versions, or optimize the C functions further) it is
|
||||
recommended to look at older CVS versions of the interesting files (just use
|
||||
ViewCVS at http://www1.mplayerhq.hu/cgi-bin/cvsweb.cgi/ffmpeg/?cvsroot=FFMpeg)
|
||||
or perhaps look into the other architecture-specific versions in i386/, ppc/,
|
||||
alpha/, ... Even if you don't understand the instructions exactly it could
|
||||
help understanding the functions & how they can be optimized.
|
||||
|
||||
NOTE:!!! if u still dont understand some function then ask at our mailing list!!!
|
||||
NOTE: If you still don't understand some function, ask at our mailing list!!!
|
||||
(http://www1.mplayerhq.hu/mailman/listinfo/ffmpeg-devel)
|
||||
|
||||
|
||||
|
||||
wtf is that function good for ....:
|
||||
the primary purpose of that list is to avoid wasting time to optimize functions
|
||||
WTF is that function good for ....:
|
||||
The primary purpose of that list is to avoid wasting time to optimize functions
|
||||
which are rarely used
|
||||
|
||||
put(_no_rnd)_pixels{,_x2,_y2,_xy2}
|
||||
used in motion compensation (en/decoding)
|
||||
Used in motion compensation (en/decoding).
|
||||
|
||||
avg_pixels{,_x2,_y2,_xy2}
|
||||
used in motion compensation of B Frames
|
||||
these are less important then the put*pixels functions
|
||||
Used in motion compensation of B-frames.
|
||||
These are less important then the put*pixels functions.
|
||||
|
||||
avg_no_rnd_pixels*
|
||||
unused
|
||||
|
||||
pix_abs16x16{,_x2,_y2,_xy2}
|
||||
used in motion estimation (encoding) with SAD
|
||||
Used in motion estimation (encoding) with SAD.
|
||||
|
||||
pix_abs8x8{,_x2,_y2,_xy2}
|
||||
used in motion estimation (encoding) with SAD of MPEG4 4MV only
|
||||
these are less important then the pix_abs16x16* functions
|
||||
Used in motion estimation (encoding) with SAD of MPEG-4 4MV only.
|
||||
These are less important then the pix_abs16x16* functions.
|
||||
|
||||
put_mspel8_mc* / wmv2_mspel8*
|
||||
used only in WMV2
|
||||
it is not recommanded that u waste ur time with these, as WMV2 is a
|
||||
ugly and relativly useless codec
|
||||
Used only in WMV2.
|
||||
it is not recommended that you waste your time with these, as WMV2
|
||||
is an ugly and relatively useless codec.
|
||||
|
||||
mpeg4_qpel* / *qpel_mc*
|
||||
use in MPEG4 qpel Motion compensation (encoding & decoding)
|
||||
the qpel8 functions are used only for 4mv
|
||||
the avg_* functions are used only for b frames
|
||||
optimizing them should have a significant impact on qpel encoding & decoding
|
||||
Used in MPEG-4 qpel motion compensation (encoding & decoding).
|
||||
The qpel8 functions are used only for 4mv,
|
||||
the avg_* functions are used only for B-frames.
|
||||
Optimizing them should have a significant impact on qpel
|
||||
encoding & decoding.
|
||||
|
||||
qpel{8,16}_mc??_old_c / *pixels{8,16}_l4
|
||||
just used to workaround a bug in old libavcodec encoder
|
||||
dont optimze them
|
||||
Just used to work around a bug in an old libavcodec encoder version.
|
||||
Don't optimize them.
|
||||
|
||||
tpel_mc_func {put,avg}_tpel_pixels_tab
|
||||
used only for SVQ3, so only optimze them if u need fast SVQ3 decoding
|
||||
Used only for SVQ3, so only optimize them if you need fast SVQ3 decoding.
|
||||
|
||||
add_bytes/diff_bytes
|
||||
for huffyuv only, optimize if u want a faster ff-huffyuv codec
|
||||
For huffyuv only, optimize if you want a faster ffhuffyuv codec.
|
||||
|
||||
get_pixels / diff_pixels
|
||||
used for encoding, easy
|
||||
Used for encoding, easy.
|
||||
|
||||
clear_blocks
|
||||
easiest, to optimize
|
||||
easiest to optimize
|
||||
|
||||
gmc
|
||||
used for mpeg4 gmc
|
||||
optimizing this should have a significant effect on the gmc decoding speed but
|
||||
its very likely impossible to write in SIMD
|
||||
Used for MPEG-4 gmc.
|
||||
Optimizing this should have a significant effect on the gmc decoding
|
||||
speed but it's very likely impossible to write in SIMD.
|
||||
|
||||
gmc1
|
||||
used for chroma blocks in mpeg4 gmc with 1 warp point
|
||||
(there are 4 luma & 2 chroma blocks per macrobock, so
|
||||
Used for chroma blocks in MPEG-4 gmc with 1 warp point
|
||||
(there are 4 luma & 2 chroma blocks per macroblock, so
|
||||
only 1/3 of the gmc blocks use this, the other 2/3
|
||||
use the normal put_pixel* code, but only if there is
|
||||
just 1 warp point)
|
||||
Note: Divx5 gmc always uses just 1 warp point
|
||||
just 1 warp point).
|
||||
Note: DivX5 gmc always uses just 1 warp point.
|
||||
|
||||
pix_sum
|
||||
used for encoding
|
||||
Used for encoding.
|
||||
|
||||
hadamard8_diff / sse / sad == pix_norm1 / dct_sad / quant_psnr / rd / bit
|
||||
specific compare functions used in encoding, it depends upon the command line
|
||||
switches which of these are used
|
||||
dont waste ur time with dct_sad & quant_psnr they arent really usefull
|
||||
Specific compare functions used in encoding, it depends upon the
|
||||
command line switches which of these are used.
|
||||
Don't waste your time with dct_sad & quant_psnr, they aren't
|
||||
really useful.
|
||||
|
||||
put_pixels_clamped / add_pixels_clamped
|
||||
used for en/decoding in the IDCT, easy
|
||||
Note, some optimized IDCTs have the add/put clamped code included and then
|
||||
put_pixels_clamped / add_pixels_clamped will be unused
|
||||
Used for en/decoding in the IDCT, easy.
|
||||
Note, some optimized IDCTs have the add/put clamped code included and
|
||||
then put_pixels_clamped / add_pixels_clamped will be unused.
|
||||
|
||||
idct/fdct
|
||||
idct (encoding & decoding)
|
||||
|
|
@ -104,31 +106,30 @@ idct/fdct
|
|||
difficult to optimize
|
||||
|
||||
dct_quantize_trellis
|
||||
used for encoding with trellis quantization
|
||||
Used for encoding with trellis quantization.
|
||||
difficult to optimize
|
||||
|
||||
dct_quantize
|
||||
used for encoding
|
||||
Used for encoding.
|
||||
|
||||
dct_unquantize_mpeg1
|
||||
used in mpeg1 en/decoding
|
||||
Used in MPEG-1 en/decoding.
|
||||
|
||||
dct_unquantize_mpeg2
|
||||
used in mpeg2 en/decoding
|
||||
Used in MPEG-2 en/decoding.
|
||||
|
||||
dct_unquantize_h263
|
||||
used in mpeg4/h263 en/decoding
|
||||
Used in MPEG-4/H.263 en/decoding.
|
||||
|
||||
FIXME remaining functions?
|
||||
btw, most of these are in dsputil.c/.h some are in mpegvideo.c/.h
|
||||
BTW, most of these functions are in dsputil.c/.h, some are in mpegvideo.c/.h.
|
||||
|
||||
|
||||
|
||||
Alignment:
|
||||
some instructions on some architectures have strict alignment restrictions,
|
||||
for example most SSE/SSE2 inctructios on X86
|
||||
the minimum guranteed alignment is writen in the .h files
|
||||
for example:
|
||||
Some instructions on some architectures have strict alignment restrictions,
|
||||
for example most SSE/SSE2 inctructios on x86.
|
||||
The minimum guaranteed alignment is written in the .h files, for example:
|
||||
void (*put_pixels_clamped)(const DCTELEM *block/*align 16*/, UINT8 *pixels/*align 8*/, int line_size);
|
||||
|
||||
|
||||
|
|
@ -136,7 +137,7 @@ for example:
|
|||
Links:
|
||||
http://www.aggregate.org/MAGIC/
|
||||
|
||||
X86 specific:
|
||||
x86-specific:
|
||||
http://developer.intel.com/design/pentium4/manuals/248966.htm
|
||||
|
||||
The IA-32 Intel Architecture Software Developer's Manual, Volume 2:
|
||||
|
|
@ -152,6 +153,5 @@ GCC asm links:
|
|||
official doc but quite ugly
|
||||
http://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
|
||||
|
||||
a bit old (note "+" is valid for input-output, even though the next says its not)
|
||||
a bit old (note "+" is valid for input-output, even though the next disagrees)
|
||||
http://www.cs.virginia.edu/~clc5q/gcc-inline-asm.pdf
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue