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• How Many Default Languages ?

  26 janvier 2012, par Multimedia Mike — Programming

  I was thinking back to my childhood, when my family first owned a computer. It was an MS-DOS-powered IBM PC. The default OS came with 2 programming environments, such as they were : GW-BASIC and batch files. It was a start, I suppose. I guess most any microcomputer you can name from that era came with some kind of BASIC interpreter. That defined the computer’s “out of the box” programmability.

  Then I started wondering how this compares to computers (operating systems/distributions, really) these days. So I installed a fresh version of the latest Ubuntu Linux version (11.10 as of this writing ; x86_32) and looked for programmability (without installing anything else). This is what I came up with :

  1. gcc/C (only the C compiler ; other components of the GNU compiler collection are installed separately)
  2. Perl
  3. Python
  4. C#, as furnished by Mono
  5. Bash — can’t forget about the shell as a full-featured programming language (sh is also present, but not t/csh)
  6. JavaScript — since Firefox is installed per default, JS counts
  7. GNU Assember — thanks to Reimar for the reminder that if gcc is present, gas necessarily needs to be there as well

  I checked on C++, Objective C, Java, Ada, Fortran, Go, Lua, Ruby, Tcl, PHP, R and other languages I could think of, but the above items were the only ones present by default. At the same time, I checked my Mac OS X (10.6) box and it also has Ruby and PHP installed. It has a bunch of other languages, courtesy of Xcode, so I can’t certify anything about its out of the box programmability.

  Still, I think “embarrassment of riches” pretty well sums it up. I try not to be crotchety old fogey complaining that kids these days don’t know how good they have it ; rather, I’m genuinely excited for anyone who wants to leap into computer programming in this day and age.

• FFMPEG - changing pixel format from 24-bit RGB to 8-bit Grayscale does not change file size

  26 septembre 2018, par Minjun Seong

  I am using the avlib* libraries and currently using the sws_getContext function to change pixel format from RGB (AV_PIX_FMT_RGB24) to grayscale (AV_PIX_FMT_GRAY8). The expected behavior should have been that the output file size should have decreased by 3 times, but it stayed the same. Furthermore, when I checked on Media-Coder to see the format, the video format was still RGB. Any ideas on why the file size didn’t change and why the file format is still RGB ?

  Note : the video DID change to black and white as expected.

• How to specify text-only subtitles in ffmpeg

  20 juin 2019, par Daniel Engel

  I’m trying to script some basic DVD-to-home media server processing. One of the things I’m trying to do, which seems like it should be pretty basic, is extract the text (srt) subtitles from the .mp4 file from the initial rip.

  I can see the stream, and if I select the stream explicitly (by stream number), I can extract it. However, I want to script the ffmpeg command. If I try to just specify the subtitle stream with a -map option, it maps the first subtitle stream, which is often a bitmap stream instead of text stream.

  So, after ripping some of my DVD’s, I’d like to process everything in a batch script, something like :

  for video in *.mp4; do
  
    ...
  
    (special code to get $subtitle filename with .srt instead of .mp4)
  
    ffmpeg -i "$video" -map 0:s "$subtitle"
  
    ...
  
  done

  I’d like the "-map" option to cause ffmpeg to select only text-based subtitles (like mov_text), and not, for example, dvd_subtitle, irrespective of which is first in the list of streams.

  Does anybody know of a way to do this ?