史蒂夫嘰嘰叫

2009年2月24日星期二

popen and mmap

轉載

http://groups.google.com/group/comp.os.linux.development.system/browse_thread/thread/113038b65f4d3257

On Sat, 24 Jan 2009 12:32:40 -0800 (PST) spasmous2 <spasm...@gmail.com> wrote:
| I want to pipe the output of a system utility to a C program I'm
| writing. I tried popen() and it works nicely. The return type is a
| FILE* which I would like to map to memory using mmap() in the
| following way:
|
| file = popen(command,"r");
|
| data = (char*)mmap(NULL, size, PROT_READ, MAP_PRIVATE, fileno
| (file), 0);
|
| However the mmap command returns an error 'No such device', which I
| looked up to mean 'The fildes parameter does not refer to a *TYPE2
| stream file (*STMF) in the "root" (/), QOpenSys, or user-defined file
| systems.'
|
| I am unsure really what this means - do you know if it's a deal
| breaker or is there a solution?

You've been told by another followup that you cannot mmap a pipe. The reason
you cannot do this is because a pipe is not data storage that can be accessed
by random position. In an extreme way, a tape could be, but even it does not
work that way with existing drivers. A pipe is a _sequential_ data stream
produced by the writing of another program.

If you want random memory access to data from another program, what you want
is a shared mapping between these programs. There are a couple ways to do
that between processes. Or you could use threads (if willing to spend time
to understand the complexities of threads).

以上的意思是說mmap不能用在任何streaming的應用

殘念

2009年2月18日星期三

PXA255 uboot

patch uboot

+===================================================================
+--- u-boot-1.1.6.orig/board/pxa255_idp/memsetup.S
++++ u-boot-1.1.6/board/pxa255_idp/memsetup.S
+@@ -41,8 +41,8 @@ DRAM_SIZE:  .long   CFG_DRAM_SIZE
+ /*
+  * 	Memory setup
+  */
+-.globl memsetup
+-memsetup:
++.globl lowlevel_init
++lowlevel_init:
+ 
+ 	mov      r10, lr
+ 
+Index: u-boot-1.1.6/include/configs/pxa255_idp.h
+===================================================================
+--- u-boot-1.1.6.orig/include/configs/pxa255_idp.h
++++ u-boot-1.1.6/include/configs/pxa255_idp.h
+@@ -41,7 +41,7 @@
+  * If we are developing, we might want to start armboot from ram
+  * so we MUST NOT initialize critical regs like mem-timing ...
+  */
+-#define CONFIG_INIT_CRITICAL			/* undef for developing */
++#undef CONFIG_INIT_CRITICAL			/* undef for developing */
+ 
+ /*
+  * define the following to enable debug blinks.  A debug blink function
============================================================

CROSS_COMPILE=arm-linux-uclibc-

make pxa255_idp_config
make all

2009年2月16日星期一

mipsel linux mplayer

Download MPlayer-1.0rc2

偶只想要decoder,所以拿掉encoder

./configure --enable-cross-compile --target=mips-linux --cc=mipsel-linux-uclibc-gcc --host-cc=gcc --disable-mencoder

make

然後錯誤出現囉

修改libavutil/internal.h
加入以下function

#if !HAVE_LLRINT
static av_always_inline long long llrint(double x)
{
return rint(x);
}
#endif /* HAVE_LLRINT */

#if !HAVE_LRINT
static av_always_inline long int lrint(double x)
{
return rint(x);
}
#endif /* HAVE_LRINT */

#if !HAVE_ROUND
static av_always_inline double round(double x)
{
return (x > 0) ? floor(x + 0.5) : ceil(x - 0.5);
}
#endif /* HAVE_ROUND */

#if !HAVE_ROUNDF
static av_always_inline float roundf(float x)
{
return (x > 0) ? floor(x + 0.5) : ceil(x - 0.5);
}
#endif /* HAVE_ROUNDF */

#if !HAVE_TRUNCF
static av_always_inline float truncf(float x)
{
return (x > 0) ? floor(x) : ceil(x);
}
#endif /* HAVE_TRUNCF */

降樣子就OK囉

mipsel-linux-uclibc-strip mplayer

將mplayer丟到target上執行

video out to framebuffer & no sound
./mplayer -vo fbdev -nosound 0001.AVI

允許丟棄frame
./mplayer -vo fbdev -nosound -framedrop ./鐵鉆山老二-43.29.mpeg

rescale to 320x240 frame rate 5, -ni是在處理不正確的avi format
./mplayer -vf scale=320:240 -fps 5 -zoom -vo fbdev -nosound -ni ./luna.avi

./mplayer -vo fbdev -nosound ./32.70_0002.wmv

連WMV都可以play,真是讚啊

Internet radio
./mplayer -playlist ../tunein-station-4.pls

# ./mplayer -vo fbdev -nosound -framedrop 五分山20080921-小黑-Skorpion001.mpeg
MPlayer 1.0rc2-3.4.6 (C) 2000-2007 MPlayer Team
CPU: SGI MIPS

Playing 五分山20080921-小黑-Skorpion001.mpeg.
MPEG-PS file format detected.
VIDEO: MPEG1 352x240 (aspect 12) 29.970 fps 1152.0 kbps (144.0 kbyte/s)
==========================================================================
Opening video decoder: [mpegpes] MPEG 1/2 Video passthrough
VDec: vo config request - 352 x 240 (preferred colorspace: Mpeg PES)
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
The selected video_out device is incompatible with this codec.
Try appending the scale filter to your filter list,
e.g. -vf spp,scale instead of -vf spp.
VDecoder init failed :(
Opening video decoder: [libmpeg2] MPEG 1/2 Video decoder libmpeg2-v0.4.0b
Selected video codec: [mpeg12] vfm: libmpeg2 (MPEG-1 or 2 (libmpeg2))
==========================================================================
Audio: no sound
Starting playback...
VDec: vo config request - 352 x 240 (preferred colorspace: Planar YV12)
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 1.30:1 - prescaling to correct movie aspect.
[swscaler @ 0xaa7440]No accelerated colorspace conversion found
[swscaler @ 0xaa7440]SwScaler: using unscaled yuv420p -> bgr565 special converter
VO: [fbdev] 352x240 => 352x270 BGR 16-bit
V: 10.5 296/296 105% 74% 0.0% 0 0

如果使用libmad
執行時加上 -ac mad

Reference

http://amoi.it168.com/blog.php?tid=321580

http://www.oppo.com/index.php?q=oppoblog/view/11752

http://people.bath.ac.uk/enpsgp/floating_point.html

http://cha.homeip.net/blog/archives/2008/03/mplayerffmpeg.html

http://blog.chinaunix.net/u1/34961/showart_494026.html

2008年12月24日星期三

nano-X JPEG display problem

1.畫面顯示只有256色

Disable fast jpeg

include/device.h

#define FASTJPEG 0 /* =1 fot temp quick jpeg 8bpp*/

2.載入大檔案時 nano-X 結束.

# /tmp/nxview /phone/media/picture/DSC_0251.JPG
Improper call to JPEG library in state 202
nxclient: lost connection to Nano-X server

Trace之後發現是memory不夠了,malloc失敗.
之後nano-X操作jpeglib的程序有問題

engine/image_jpeg.c

int
GdDecodeJPEG(buffer_t * src, PMWIMAGEHDR pimage, PSD psd, MWBOOL fast_grayscale)
{
.....
.....
.....
    /* Step 5: Start decompressor */
    jpeg_start_decompress (&cinfo);

    /* Step 6: while (scan lines remain to be read) */
    while(cinfo.output_scanline < cinfo.output_height) {
        JSAMPROW rowptr[1];
        rowptr[0] = (JSAMPROW)(pimage->imagebits +
            cinfo.output_scanline * pimage->pitch);
        jpeg_read_scanlines (&cinfo, rowptr, 1);
    }
    ret = 1;
#if 1 /*Modify by Steve*/ <<--改到這裡就OK啦
/* Step 7: Finish decompression */
jpeg_finish_decompress (&cinfo);
#endif
err:
#if 0 /*Modify by Steve*/ <<--就是這裡囉
    /* Step 7: Finish decompression */
    jpeg_finish_decompress (&cinfo);
#endif
    /* Step 8: Release JPEG decompression object */
    jpeg_destroy_decompress (&cinfo);

    /* May want to check to see whether any corrupt-data
    * warnings occurred (test whether jerr.pub.num_warnings is nonzero).
    */
    return ret;
}
#endif /* MW_FEATURE_IMAGES && defined(HAVE_JPEG_SUPPORT)*/

3.圖檔太大會因為memory不夠而無法顯示

解決方式是在jepglib decompress 時作 scaling

engine/image_jpeg.c

int
GdDecodeJPEG(buffer_t * src, PMWIMAGEHDR pimage, PSD psd, MWBOOL fast_grayscale)
{
.....
.....
.....

    jpeg_calc_output_dimensions(&cinfo);

#if 1
int wfac, hfac, fac;
wfac = cinfo.output_width / psd->xres;
hfac = cinfo.output_height / psd->yres;
fac = wfac;
if(fac > hfac)
    fac = hfac;
if(fac > 8) fac = 8; /* 1/8 */
else if(fac > 4) fac = 4; /* 1/4 */
else if(fac > 2) fac = 2; /* 1/2 */
else fac = 1; /*No scaling*/

cinfo.scale_num = 1;
cinfo.scale_denom = fac;
cinfo.dct_method = JDCT_FASTEST;
cinfo.do_fancy_upsampling = FALSE;

jpeg_calc_output_dimensions(&cinfo);
#endif

.....
.....
.....
}
#endif /* MW_FEATURE_IMAGES && defined(HAVE_JPEG_SUPPORT)*/

2008年12月23日星期二

Redirect printf to file

#include <stdio.h>
#include <stdlib.h>

FILE *fp;
fp = freopen("/tmp/dock.log", "w", stdout);

printf("printf to /tmp/dock.log ...\n");

fclose(fp);

2008年12月10日星期三

nano-X Window Manager

nano-X並沒有自動處理視窗在screen繪圖的動作,例如A視窗有部份區域與B視窗重疊,當A視窗結束消失,B視窗被A視窗覆蓋的部份會是一片空白.

在nano-X上實作一個Window Manager才能解決上述的問題.
nano-X中的nanowm可作為參考.

nano-X 提供了Graphic UI所需要的基礎功能,大致上可分為

1.操作繪圖區域
GrNewWindow
GrNewPixmap
GrMapWindow
GrUnmapWindow
GrReparentWindow
GrCopyArea
GrClearArea
2.繪圖物件 Graphic Context
GrNewGC
GrCopyGC
GrForeground
GrBackground
GrSetGCFont
3.繪圖工具
GrLine
GrRect
GrPoly
GrFillRect
GrFillPoly
4.繪圖區域狀態管理,回報視窗顯示,子視窗狀態更新等
GrCheckNextEvent

實做Window Manager之前必須了解的事情
0.視窗具有父子階層的關係,子視窗的x,y軸位置是相對於父視窗.父視窗的大小範圍就是子視窗的可視繪圖範圍
1.GR_ROOT_WINDOW_ID代表系統中最底層的視窗即root window,可當作桌面來看待.
2.視窗分為兩種Container Window與Client Window,
Container Window其父視窗為root window.
Client window其父視窗為Container Window.
3.Window Manager需要處理視窗Event.
此功能為實做Window Manager最重要的部份.關係到視窗的正確顯示.

GR_EVENT_TYPE_EXPOSURE :
視窗需要重繪.

GR_EVENT_TYPE_CHLD_UPDATE :
子視窗狀態改變了.
若子視窗隱藏(unmap),父視窗為Container Window則重繪父視窗.

2008年12月5日星期五

軟體開發文章

閱讀他人的程式碼(1)─讀懂程式碼，使心法皆為我所用

http://www.ithome.com.tw/itadm/article.php?c=47717

不會寫程式但是在做系統分析 有沒有不會寫程式卻在做系統分析的？ [精華]

http://funp.com/push/index.php?tag=%E7%A8%8B%E5%BC%8F&hot=&stars=1&page=11#p=81693

強化程式可讀性，以提升開發的效率

http://www.ithome.com.tw/itadm/article.php?c=52029

管理者要懂得如何用嘴巴寫程式

http://www.ithome.com.tw/itadm/article.php?c=51771

註解不是換句話說，是補程式的不足

http://www.ithome.com.tw/itadm/article.php?c=51597

打造穩固程式碼，先從思路方向著手

http://www.ithome.com.tw/itadm/article.php?c=51397

當程式人「晉升」至管理階級

http://www.ithome.com.tw/itadm/article.php?c=51133

程式設計的2大面向：演算和架構

http://www.ithome.com.tw/itadm/article.php?c=49841

GUI的開發瓶頸

http://www.ithome.com.tw/itadm/article.php?c=49436

漫談程式碼的相依性 (1)時時關注類別的相依程度、持續改善

http://www.ithome.com.tw/itadm/article.php?c=49179

程式碼的演化之路(1)持續讓程式碼保持進步的能力

http://www.ithome.com.tw/itadm/article.php?c=48746

程式設計2.0 (1)善用優質網站資源，快速上手新技術

http://www.ithome.com.tw/itadm/article.php?c=47405

物件導向程式設計常見的錯誤(1)抽離作用重複的程式碼，重構品質

http://www.ithome.com.tw/itadm/article.php?c=45745

物件導向與封裝

http://www.ithome.com.tw/itadm/article.php?c=45903

訂閱：文章 (Atom)

2009年2月24日 星期二

2009年2月18日 星期三

2009年2月16日 星期一

2008年12月24日 星期三

2008年12月23日 星期二

2008年12月10日 星期三

2008年12月5日 星期五