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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.

• tablegen : Don’t use cbrtf in host tools

  15 janvier 2013, par Derek Buitenhuis

  tablegen : Don’t use cbrtf in host tools
  You cannot count on them being present on all systems, and you
  
  cannot include libm.h in a host tool, so just hard code baseline
  
  implementations.
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DBH] libavcodec/cbrt_tablegen.h
  • [DBH] libavcodec/mpegaudio_tablegen.h

• FFmpeg RTP network issue in Ubuntu

  4 mai 2017, par Ivan Kolesnikov

  I want to copy a bunch of SD sources from mpegts transported with RTP on local files. (VBR mpeg2video, mp2 audio). It works fine for one multicast source with the following command :

  ffmpeg -i rtp://@IP1:PORT -c copy video1.mpg

  but when I ran a second ffmpeg instance with the following command :

  ffmpeg -i rtp://@IP2:PORT -c copy video2.mpg

  then I got errors from both FFmpeg instances ("RTP : dropping old packet received too late") and in both files (video1.mpg and video2.mpg) recorded video from the second source (rtp ://@IP2:PORT).

  This issue occurs only in Linux (I checked Ubuntu 14.04 - 16.04). I have no problems in Windows and can transcoding video correctly in parallel from files. Under Ubuntu even two ffplay instances tuned to different sources play back the same content (from the source which was opened last). I tried playing back with VLC and there is no such problem.

  I can resolve this issue when using FFmpeg with the -f option :
  ffmpeg -f mpegts -i rtp ://@IP1:PORT -c copy video1.mpg
  and
  ffmpeg -f mpegts -i rtp ://@IP2:PORT -c copy video2.mpg, but then I’m getting the following errors : "[mpegts @ 0x306e240] PES packet size mismatch" and receive both files (video1.mpg and video2.mpg) with artifacts and freeze effects. This issue appears for both operating systems.

  How can I record|transcode videos from multiple RTP streams with FFmpeg simultaneously under Ubuntu without errors and artifacts ?