spelling/wording/grammar

Originally committed as revision 4367 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg_powerpc_performance_evaluation_howto.txt

@@ -8,7 +8,7 @@ I - Introduction
 
 The PowerPC architecture and its SIMD extension AltiVec offer some
 interesting tools to evaluate performance and improve the code.
-This document try to explain how to use those tools with FFmpeg.
+This document tries to explain how to use those tools with FFmpeg.
 
 The architecture itself offers two ways to evaluate the performance of
 a given piece of code:
@@ -16,31 +16,31 @@ a given piece of code:
 1) The Time Base Registers (TBL)
 2) The Performance Monitor Counter Registers (PMC)
 
-The firsts are always available, always active, but they're not very
-accurate : the registers increment by one every four *bus* cycle. On
-my 667 Mhz tibook (ppc7450) , this means once every twenty *processor*
-cycle. So we won't use that.
+The first ones are always available, always active, but they're not very
+accurate: the registers increment by one every four *bus* cycles. On
+my 667 Mhz tiBook (ppc7450), this means once every twenty *processor*
+cycles. So we won't use that.
 
-The PMC are much more useful : not only they can report cycle-accurate
+The PMC are much more useful: not only can they report cycle-accurate
 timing, but they can also be used to monitor many other parameters,
-such as the number of AltiVec stalls for every kind of instructions,
+such as the number of AltiVec stalls for every kind of instruction,
 or instruction cache misses. The downside is that not all processors
 support the PMC (all G3, all G4 and the 970 do support them), and
 they're inactive by default - you need to activate them with a
-dedicated tool. Also, the number of available PMC depend on the
-procesor : the various 604 have 2, the various 75x (aka. G3) have 4,
-anbd the various 74xx (aka G4) have 6.
+dedicated tool. Also, the number of available PMC depends on the
+procesor: the various 604 have 2, the various 75x (aka. G3) have 4,
+and the various 74xx (aka G4) have 6.
 
-*WARNING*: The powerpc 970 is not very well documented, and its PMC
-registers are 64bits wide. To properly notify the code, you *must*
-tune for the 970 (using --tune=970), or the code will assume 32bits
+*WARNING*: The PowerPC 970 is not very well documented, and its PMC
+registers are 64 bits wide. To properly notify the code, you *must*
+tune for the 970 (using --tune=970), or the code will assume 32 bit
 registers.
 
 
 II - Enabling FFmpeg PowerPC performance support
 
-This need to be done by hand. First, you need to configure FFmpeg as
-usual, plus using the "--powerpc-perf-enable". for instance :
+This needs to be done by hand. First, you need to configure FFmpeg as
+usual, but add the "--powerpc-perf-enable" option. For instance:
 
 #####
 ./configure --prefix=/usr/local/ffmpeg-cvs --cc=gcc-3.3 --tune=7450 --powerpc-perf-enable
@@ -48,8 +48,8 @@ usual, plus using the "--powerpc-perf-enable". for instance :
 
 This will configure FFmpeg to install inside /usr/local/ffmpeg-cvs,
 compiling with gcc-3.3 (you should try to use this one or a newer
-gcc), and tuning for the PowerPC7450 (i.e. the newer G4 ; as a rule of
-thumb, those at 550Mhz and more). It will also enables the PMCs.
+gcc), and tuning for the PowerPC 7450 (i.e. the newer G4; as a rule of
+thumb, those at 550Mhz and more). It will also enable the PMC.
 
 You may also edit the file "config.h" to enable the following line:
 
@@ -59,24 +59,24 @@ You may also edit the file "config.h" to enable the following line:
 
 If you enable this line, then the code will not make use of AltiVec,
 but will use the reference C code instead. This is useful to compare
-performance between the two versions of the code.
+performance between two versions of the code.
 
-Also, the number of enabled PMC is defined in "libavcodec/ppc/dsputil_ppc.h" :
+Also, the number of enabled PMC is defined in "libavcodec/ppc/dsputil_ppc.h":
 
 #####
 #define POWERPC_NUM_PMC_ENABLED 4
 #####
 
-If you have a G4 cpus, you can enable all 6 PMCs. DO NOT enable more
-PMCs than available on your cpu !
+If you have a G4 CPU, you can enable all 6 PMC. DO NOT enable more
+PMC than available on your CPU!
 
-Then, simply compile ffmpeg as usual (make && make install).
+Then, simply compile FFmpeg as usual (make && make install).
 
 
 
 III - Using FFmpeg PowerPC performance support
 
-This FFmeg can be used exactly as usual. But before exiting, Ffmpeg
+This FFmeg can be used exactly as usual. But before exiting, FFmpeg
 will dump a per-function report that looks like this:
 
 #####
@@ -99,16 +99,16 @@ PowerPC performance report
 #####
 
 In this example, PMC1 was set to record CPU cycles, PMC2 was set to
-record AltiVec Permute Stall Cycle, and PMC3 was set to record AltiVec
+record AltiVec Permute Stall Cycles, and PMC3 was set to record AltiVec
 Issue Stalls.
 
 The function "gmc1_altivec" was monitored 255302 times, and the
 minimum execution time was 231 processor cycles. The max and average
 aren't much use, as it's very likely the OS interrupted execution for
-reasons of it's own :-(
+reasons of its own :-(
 
-With the exact same setting and source file, but using the reference C
-code we get :
+With the exact same settings and source file, but using the reference C
+code we get:
 
 #####
 PowerPC performance report
@@ -134,27 +134,27 @@ the fastest C execution in this example. It's not perfect but it's not
 bad (well I wrote this function so I can't say otherwise :-).
 
 Once you have that kind of report, you can try to improve things by
-finding what goes wrong and fixing it ; in the example above, one
-shoud try to diminish the number of AltiVec stalls, as this *may*
-improve performances.
+finding what goes wrong and fixing it; in the example above, one
+should try to diminish the number of AltiVec stalls, as this *may*
+improve performance.
 
 
 
-IV) Enabling the PMC in MacOS X
+IV) Enabling the PMC in Mac OS X
 
 This is easy. Use "Monster" and "monster". Those tools come from
 Apple's CHUD package, and can be found hidden in the developer web
-site & ftp site. "MONster" is the graphical application, use it to
+site & FTP site. "MONster" is the graphical application, use it to
 generate a config file specifying what each register should
 monitor. Then use the command-line application "monster" to use that
 config file, and enjoy the results.
 
-Note that "MONster" can be used for many other stuff, but it's
+Note that "MONster" can be used for many other things, but it's
 documented by Apple, it's not my subject.
 
 
 
-V) Enabling the PMC in Linux
+V) Enabling the PMC on Linux
 
 I don't know how to do it, sorry :-) Any idea very much welcome.