Recover file name copied from iPod/iPhone

With gtkPod, we are able to connect to iPhone/iPod and copy all the files, but the filenames are all cryptic (they are all in four letters). With the following script, we can recover the file names and convert them into readable format in the form of "artist - album" pattern.

#!/bin/sh
FULLPATH=$1
FILE=${FULLPATH##*/}
FILENAME=${FILE%.*}
EXT=${FILE##*.}
#echo "FILENAME=$FILENAME"
#echo "EXTension=$EXT"
shift
OPTS=$@
echo filename=$FILENAME

meta=`mp4info "$FULLPATH" | awk '/Metadata / {sub(/^[ \t]+/, "")};1'`
#echo meta=$meta
TITLE=`echo "$meta" | awk '/Metadata Name: / {gsub(/Metadata Name: /,""); print }'`
ARTIST=`echo "$meta" | awk '/Metadata Artist: / {gsub(/Metadata Artist: /,""); print }'`

if [ -z "$TITLE" ]
then
 TITLE="unknown"
else
 echo TITLE=$TITLE
fi

if [ -z "$ARTIST" ]
then
 ARTIST="unknown"
else
 echo ARTIST=$ARTIST
fi

TARGET="$ARTIST - $TITLE.$EXT"
cp "$FULLPATH" "$TARGET"

if [ -n $ "$TARGET" ]
then
 rm "$FULLPATH"
fi

Save the above script into an executable file, say mp4fixname.

To fix a filename, just run it and pass the encoded filename.
For example, if the file name is NXJA.m4a, we just run the script as below:


mp4fixname NXJA.m4a

The original filename will be replaced in artist and song name format according to metadata/tags stored in the original file.

Converting m4a song to mp3 format

Sometimes, I need to convert files I bought from iTunes to MP3 format. Well, actually not all songs we buy convertable to MP3. Only non-DRM format (with m4a extension) can be converted. The protected format with m4p extension still cannot be converted, theoritically at least (there is a hack to remove the DRM. But that's not easy and won't be covered here).

The following script converts an MP4 file to MP3 format.
It copies all the tags stored in the original file into the target file.
Make sure you have ffmpeg, mp4info, awk, and bc installed.

#!/bin/bash

#!/bin/bash

FULLPATH=$1
file=${FULLPATH##*/}
FILENAME=${file%.*}
EXT=${file##*.}
#echo "FILENAME=$FILENAME"
#echo "EXTension=$EXT"
shift
OPTS=$@

if [ `echo $EXT | tr [:upper:] [:lower:]` = "m4a" ]
then
 bitratekbps=`mp4info "$FULLPATH" | awk '$1 ~ /([0-9]+) kbps/g {print $8}'`
 bitratebps=`echo "scale=10; $bitratekbps*1000" | bc -l`
 hz=`mp4info "$FULLPATH" | awk '$1 ~ /([0-9]+) kbps/g {print $10}'`

 ffmpeg -i "$FILENAME.m4a" -aq 1 -ab $bitratebps -ar $hz -f mp3 \
        -metadata major_brand="MP3" \
         -metadata compatible_brands="MP3 libmp3lame" \
        "$FILENAME.mp3" $OPTS
fi

Save the file, say, to m4a2mp3 and make it executable.

To convert a song:

m4a2mp3 song.m4a

The target file name is the same, except the extension now is MP3. Also, some tags/metadata are replaced to reflect the new format. If you want to add other options, you can put that after file name. For example: m4a2mp3 song.m4a -metadata mymeta="converted from m4a"

Assembly in Linux

section .data
    hello:     db 'Hello world!',10    ; 'Hello world!' plus a linefeed character
    helloLen:  equ $-hello             ; Length of the 'Hello world!' string

section .text
    global _start

    _start:
    mov ecx,5            ; display the string 5 times

_loop:
    mov eax,4            ; The system call for write (sys_write)
    mov ebx,1            ; File descriptor 1 - standard output
    push ecx             ; save ecx as it is gonna be used as param to sys_write
    mov ecx,hello        ; Put the offset of hello in ecx
    mov edx,helloLen     ; helloLen is a constant, so we don't need to say
                         ;  mov edx,[helloLen] to get it's actual value
    int 80h              ; Call the kernel
    pop ecx              ; restore ecx (counter)
    loop _loop
    mov eax,1            ; The system call for exit (sys_exit)
    mov ebx,0            ; Exit with return code of 0 (no error)
    int 80h


Steps:
Save the file as syscall.asm  
Execute: nasm -f elf syscall.asm  
Execute: ld -s -o syscall syscall.o  
run it as: ./syscall   
To check the object file, we can use objdump, elfdump, or readelf. For example:  


$ readelf -a ./syscall.o
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           Intel 80386
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          0 (bytes into file)
  Start of section headers:          64 (bytes into file)
  Flags:                             0x0
  Size of this header:               52 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0
  Size of section headers:           40 (bytes)
  Number of section headers:         7
  Section header string table index: 3

Section Headers:
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al

  [ 0]                   NULL            00000000 000000 000000 00      0   0  0

  [ 1] .data             PROGBITS        00000000 000160 00000d 00  WA  0   0  4

  [ 2] .text             PROGBITS        00000000 000170 00002b 00  AX  0   0 16

  [ 3] .shstrtab         STRTAB          00000000 0001a0 000031 00      0   0  1

  [ 4] .symtab           SYMTAB          00000000 0001e0 000080 10      5   7  4

  [ 5] .strtab           STRTAB          00000000 000260 000029 00      0   0  1

  [ 6] .rel.text         REL             00000000 000290 000008 08      4   2  4
$ readelf -a ./syscall.o
ELF Header:s:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF32unknown)
  Data:                              2's complement, little endianpecific)
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           Intel 80386
  Version:                           0x1 0x290 contains 1 entries:
  Entry point address:               0x0Value  Sym. Name
  Start of program headers:          0 (bytes into file)
  Start of section headers:          64 (bytes into file)
  Flags:                             0x0e.
  Size of this header:               52 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0Vis      Ndx Name
  Size of section headers:           40 (bytes)UND
  Number of section headers:         7DEFAULT  ABS syscall.asm
  Section header string table index: 3DEFAULT    1
     3: 00000000     0 SECTION LOCAL  DEFAULT    2
Section Headers:     0 NOTYPE  LOCAL  DEFAULT    1 hello
  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
  [ 0]                   NULL            00000000 000000 000000 00      0   0  0
  [ 1] .data             PROGBITS        00000000 000160 00000d 00  WA  0   0  4
  [ 2] .text             PROGBITS        00000000 000170 00002b 00  AX  0   0 16
  [ 3] .shstrtab         STRTAB          00000000 0001a0 000031 00      0   0  1
  [ 4] .symtab           SYMTAB          00000000 0001e0 000080 10      5   7  4
  [ 5] .strtab           STRTAB          00000000 000260 000029 00      0   0  1
  [ 6] .rel.text         REL             00000000 000290 000008 08      4   2  4
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

There are no section groups in this file.

There are no program headers in this file.

Relocation section '.rel.text' at offset 0x290 contains 1 entries:
 Offset     Info    Type            Sym.Value  Sym. Name
00000011  00000201 R_386_32          00000000   .data

There are no unwind sections in this file.

Symbol table '.symtab' contains 8 entries:
   Num:    Value  Size Type    Bind   Vis      Ndx Name
     0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 00000000     0 FILE    LOCAL  DEFAULT  ABS syscall.asm
     2: 00000000     0 SECTION LOCAL  DEFAULT    1
     3: 00000000     0 SECTION LOCAL  DEFAULT    2
     4: 00000000     0 NOTYPE  LOCAL  DEFAULT    1 hello
     5: 0000000d     0 NOTYPE  LOCAL  DEFAULT  ABS helloLen
     6: 00000005     0 NOTYPE  LOCAL  DEFAULT    2 _loop
     7: 00000000     0 NOTYPE  GLOBAL DEFAULT    2 _start

No version information found in this file.

Relacing OpenJDK with Oracle/Sun Java SDK as default java

According to some sources, Sun/Oracle JDK or JRE is slightly faster than OpenJDK.  To install the SunJDK without removing the OpenJDK is as follow:

1. Download the SDK from here
2. Install the SDK.  For example: sudo rpm -Uvih <sdk rpmfile> or sudo sh ./<sdk bin file>
3. Once it is installed, copy-paste the following script and execute it

#!/bin/sh

for FP in /usr/java/default/bin/* ; do
    NAME=${FP##*/}
    echo installing $NAME
    sudo alternatives --install /usr/bin/${NAME} ${NAME} /usr/java/default/bin/${NAME} 20000
    alternatives --display "${NAME}" | grep "${NAME}"
done

New Nook v.s. Amazon Kindle

Today I went to Barnes & Noble store and attracted with a Nook display. Coincidentally, I was also carrying my Kindle with me, so now I have a chance to compare it visually. First of all, the overall physical size of the new Nook is smaller than Kindle, because it has got rid of physical keyboard. Instead, a visual keyboard would be displayed whenever needed. As you might have known, this new Nook is now equipped with touch screen and I guess it is capacitive touch screen as it is very responsive. The screen area is actually about the same as Kindle's screen.

For the resolution, Kindle is tad better. This is based on my visual check by starring at each screen very closely (I got to remove my glasses to get better visual). Letters on Kindle are darker and smoother (but not much better), but Nook screen is whiter. Screen refresh rate (refresh between page) is faster on the Nook. Page buttons are located the same as Kindle (page-up and page-down are on left and right edge of the body). For the weight, I guess Kindle is slightly lighter on my hand, but it's hard to make a correct and accurate judgment without put them on scale.

Something interesting is the power life. Nook is apparently is the winner, at least according to the sales person. It can last up to 2 months with Wi-Fi turned off, while on Kindle is about a month. Price wise, Kindle is a bit cheaper, especially if we're OK with ads-supplied screen-saver version of it. On Amazon website, the ads-supported version is $114 (with no sales tax if we buy from California, and no shipping cost), while the Nook is $139 + sales tax. The web browser on Nook is better.

For the collection of books available, Amazon seems has little bit more selection, but B&N is catching up quickly too. A feature that's not available on Kindle is "Rent" and "Read in store", and this would make Nook very appealing for some users who want to borrow a book from friend or just want to read a book in B&N store (although not all e-books can be read or rented). I hope Amazon will match it with the similar offering. Nook is also EPUB-compatible reader, while Amazon's Kindle uses a proprietary format (Mobile-pocket-based MOBI format with DRM added). While many books can be converted with a tool such as Calibre (EPUB to MOBI and vice versa), others are nonconvertible.

Internally, they both are based on Linux, although Nook is Android-base. No surprise the Nook is faster because it uses more recent hardware, while Kindle has been a year old in the market. I think Amazon is preparing a next gen one. Just wait and see a couple of months as rumors say the will introduce the new one. The rumor also says Kindle might have a touch screen too (some people in the internet forum wish Amazon not to arm it with a touch screen. I don't understand what's the reason behind it yet).

Overall, I guess they tie in many comparisons. Only our preferences can tell which one to buy. If I haven't had Kindle, I might buy this new Nook because it's cute (very portable and almost fit in my shirt pocket) and has some features not available on Kindle.

=-=-=-=-=
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Fedora 15 & GNOME 3 Crash.

Some PCs have issues when installed with Fedora 15 and GNOME 3 as its desktop manager.  On my Compaq Presario R3000 labptop, I was unable to login due to crash in subsystem (gnome-shell).  When I tried to login, it display a message something like "unrecovered ...".

The problem is that GNOME3 is not stable enough to be run on some machines/video cards with 3D (perhaps Nouveau driver unable to execute 100% of the required GNOME3 features?).  Some people in the Internet said that by executing the following command it should fix the issue, but not in my case:

gsettings set org.gnome.desktop.session session-name gnome-fallback

After googling around, I found a good solution:

sudo rpm --nodeps -e gnome-shell

This has fixed my GNOME problem.  I could now login to the fallback mode (GNOME2-like)