HOWTO: force filesystem check on reboot in MS Windows (NT family)

These tricks may be well-known, but still handy for busy volumes (e. g., the system one):

0. Open a command prompt (cmd) with administrator privileges (either via "Start → Run..." menu, "<WinKey> + <R>" hotkey, or other methods you like).
1. Two options.
   1. Marking volume "dirty":

      > fsutil dirty set C:
      Volume - C: is now marked dirty
      

   2. A milder option, just scheduling the volume to be checked on startup:

      > chkntfs /C C:
      
      

2. Reboot safely.
3. Watch the CHKDSK operation progress...
4. DONE!
   (You can check the CHKDSK logs later in the "Event Viewer" (eventvwr.msc or simply eventvwr for short)).

References:

• MS TechNet Library - Windows Server:
  • Chkntfs
  • Fsutil dirty
• MS Knowledge Base:
  • CHKNTFS.EXE: What You Can Use It For
• MS Windows XP Professional Product Documentation:
  • Microsoft Windows XP - Chkntfs
  • Microsoft Windows XP - Fsutil: dirty

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Last updated: 2016-05-20

Hints: D-Link ADSL router: time to change the power adapter

Sample device: D-Link DSL-2640* (quite old combined ADSL modem / Ethernet switch / Wi-Fi router); should probably work for some other Linux-based routers with Broadcom chips.

Some trouble signs include: red power lights, not booting into the normal working mode (or booting into the recovery one) after power-on; slowing down of the operation, decrease of the performance & significant packet dropping rate; unexpected restarts etc.

Reliable internal software (firmware) symptoms — specific log strings get triggered, e. g.:

• accessed via the web-based interface:

  System Log

  Date/Time	Facility	Severity	Message
  .	.	.	.
  Jan 1 00:01:23	user	warn	kernel: - Power glitch detected. Duration: 5 us

• and via Telnet / SSH:

  ...
  > sh
  ...
  # dmesg
  ...
   - Power glitch detected. Duration: 6 us
  ...
  

  • Note: reportedly, some users also observe another diagnostic log message:

     - Power failure detected. ADSL Link down.

What to do:

1. check the power cabling (and fix it, if needed);
2. check the electrolytic capacitors:
   1. inside the power adapter,
   2. and in the router itself,
   3. and replace (resolder) the blown-up ones with new ones (paying attention to the nominal values, indeed);
3. buy a new power adapter, if needed.

Safety notes:

• BEWARE of electric shock.
• Disconnect the AC power before opening the cases.
• Some technical experience needed.

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Last updated: 2015-11-30

HOWTO: get rid of packed B-frames in AVI (MPEG-4 Visual) video with FFmpeg

You've probably seen some AVI (Audio Video Interleave) files with MPEG-4 video (more specifically, MPEG-4 Visual / ASP, usually encoded by DivX or Xvid codecs) inside; they are often used for DVD-rips. Such AVI video files often contain "packed B-frames", which is not an optimal frame storage way, but just a workaround for the VfW (Video for Windows) framework shortcomings (i. e., bugs).
To ensure you have a "bad-style" MPEG-4 AVI file, you can check it with a media analyzer utility like MediaInfo (in this case, it'll show you something like "Muxing mode : Packed bitstream").
Fortunately, that wrong thing is easy to "unpack" with an up-to date version of FFmpeg (v2.7+):

$ ffmpeg -i in_bad.avi -codec copy -bsf:v mpeg4_unpack_bframes out_good.avi

The conversion is lossless (neither video nor audio quality is harmed; the file should remain compatible with the hardware players... or even become more compatible), but often can even reduce the resulting AVI container size.

BTW, after "bitstream unpacking", the MPEG-4 video stream becomes standards-compliant, so you can put it directly into the popular MP4 container without transcoding (but it requires the audio stream to be MP4-compatible too, e. g. MP3 is OK);
e. g., here are 2.5 3 remuxing examples using the same FFmpeg:

$ ffmpeg -i in10_good.avi -codec copy out10_good.mp4
$ ffmpeg -i in20_bad.avi -codec copy -bsf:v mpeg4_unpack_bframes out20_better.mp4
$ ffmpeg -i in20_bad.avi -codec copy -bsf:v mpeg4_unpack_bframes -movflags faststart out25_best.mp4

You can download the source code and binary builds of the current FFmpeg (for MS Windows, Apple Mac OS X and Linux) freely from the official site.
Usually, you will find a compatible version in the repositories of your favorite Linux distribution;
however, in Debian, it's available only starting from the release 9 "Stretch" (and fortunately, it's currently in the backports for 8 "Jessie" too; and for use in Ubuntu, you need release 15.10 "Wily Werewolf", at least):

# sudo apt-get install ffmpeg

References:

1. FFmpeg
   1. FFmpeg Bitstream Filters Documentation
   2. Download FFmpeg
   3. FFmpeg Changelog
   4. #2913 (Bitstream filter to fix "invalid and inefficient vfw-avi packed B frames") – FFmpeg
2. MediaInfo
3. Debian Package Tracker - ffmpeg
4. ffmpeg package : Ubuntu
5. Wikipedia
   1. Ripping
   2. MPEG-4 Part 2
   3. DivX
   4. Xvid
   5. Audio Video Interleave
   6. Video for Windows
   7. Video compression picture types
   8. Inter frame

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Last updated: 2017-12-28

Tips: where to find the photos in your Google account

You can try to find your photos in different "departments" of your Google account:

• Photos - Google Photos
  • Albums - Google Photos
• Google Album Archive
• Google Dashboard (see the "Photos" count)
• Download your data [Google Takeout] (refer to the "Google Photos" section)
• Google Photos - Google Drive (somewhat deprecated)
• Photos - Google+ (discontinued)
• Picasa Web Albums (the classic option; unfortunately, discontinued)

And don't forget about the trash folder(s):

• Trash - Google Photos
• Trash - Google Drive
• Photos - Google+ (discontinued)

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Last updated: 2018-03-01

Overview: barcode reading software in Linux

• libdmtx
  • Supports: Data Matrix.
  • Utilities: dmtxread (reads barcodes from image files), dmtxwrite (writes barcodes to image files).
• ZBar
  • Recognizes: EAN-13, EAN-8, UPC-A, UPC-E, Code 128, Code 39, Interleaved 2 of 5 and QR code.
  • Utilities: zbarimg (reads barcodes from image files), zbarcam (reads barcodes from video devices).

Tested in Debian Jessie:

# apt-get install dmtx-utils zbar-tools