diff --git a/doc/optimization.txt b/doc/optimization.txt index f435d0f0cb..d5ae06d76d 100644 --- a/doc/optimization.txt +++ b/doc/optimization.txt @@ -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 -