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• What Every Programmer Should Know

  24 décembre 2012, par Multimedia Mike — General

  During my recent effort to force myself to understand Unicode and modern text encoding/processing, I was reminded that this is something that “every programmer should just know”, an idea that comes up every so often, usually in relation to a subject in which the speaker is already an expert. One of the most absurd examples I ever witnessed was a blog post along the lines of “What every working programmer ought to know about [some very specific niche of enterprise-level Java programming]“. I remember reading through the article and recognizing that I had almost no knowledge of the material. Disturbing, since I am demonstrably a “working programmer”.

  For fun, I queried the googles on the matter of what ever programmer ought to know.

  Specific Topics
  Here is what every programmer should know about : Unicode, time, memory (simple), memory (extremely in-depth), regular expressions, search engine optimization, floating point, security, basic number theory, race conditions, managed C++, VIM commands, distributed systems, object-oriented design, latency numbers, rate monotonic algorithm, merging branches in Mercurial, classes of algorithms, and human names.

  Broader Topics
  20 subjects every programmer should know, 97 things every programmer should know, 12 things every programmer should know, things every programmer should know (27 items), 10 papers every programmer should read at least twice, 10 things every programmer should know for their first job.

  Meanwhile, I remain fond of this xkcd comic whose mouseover text describes all that a person genuinely needs to know. Still, the new year is upon us, a time when people often make commitments to bettering themselves, and it couldn’t hurt (much) to at least skim some of the lists and find out what you never knew that you never knew.

  What About Multimedia ?
  Reading the foregoing (or the titles of the foregoing pieces), I naturally wonder if I should write something about what every programmer should know about multimedia. I think it would look something like a multimedia programming FAQ. These are some items that I can think of :

  1. YUV : The other colorspace (since most programmers are only familiar with RGB and have no idea what to make of the YUV that comes out of most video decoding APIs)
  2. Why you can’t easily seek randomly to any specific frame in a video file (keyframe/interframe discussion and their implications)
  3. Understand your platform before endeavoring to implement multimedia software (modern platforms, particularly mobile platforms, probably provide everything you need in the native APIs and there is likely little reason to compile libavcodec for the platform)
  4. Difference between containers and codecs (longstanding item, but I would argue it’s less relevant these days due to standardization on the MPEG — MP4/H.264/AAC — stack)
  5. What counts as a multimedia standard in this day and age (comparing the foregoing MPEG stack with the WebM/VP8/Vorbis stack)
  6. Trade-offs to consider when engineering a multimedia solution
  7. Optimization doesn’t always work the way you think it does (not everything touted as a massive speed-up in the world of computing — whether it be multithreaded CPUs, GPGPUs, new SIMD instruction sets — will necessarily be applicable to multimedia processing)
  8. A practical guide to legal issues would not be amiss
  9.  ???

  What other items count as “something multimedia-related that every programmer should know” ?

• ffmpeg error creating thumbnail different frame rate

  18 décembre 2012, par KJS

  When using this at the command line I get very bad images with only grey or stripes in them.
  It seems "the frame rate differs from container frame rate : 59.94 (60000/1001) -> 29.97 (30000/1001)".

  Is there any way I can fix this in the ffmpeg statement ?

  ffmpeg -ss 00:00:10 -i FILENAME.mp4 -vframes 1 FILENAME.jpg

  This is the output I get :

  FFmpeg version 0.5.2, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  
    configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 --mandir=/usr/share/man --incdir=/usr/include --disable-avisynth --extra-cflags=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC --enable-avfilter --enable-avfilter-lavf --enable-libdirac --enable-libfaac --enable-libfaad --enable-libfaadbin --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libx264 --enable-gpl --enable-nonfree --enable-postproc --enable-pthreads --enable-shared --enable-swscale --enable-vdpau --enable-version3 --enable-x11grab
  
    libavutil     49.15. 0 / 49.15. 0
  
    libavcodec    52.20. 1 / 52.20. 1
  
    libavformat   52.31. 0 / 52.31. 0
  
    libavdevice   52. 1. 0 / 52. 1. 0
  
    libavfilter    0. 4. 0 /  0. 4. 0
  
    libswscale     0. 7. 1 /  0. 7. 1
  
    libpostproc   51. 2. 0 / 51. 2. 0
  
    built on Jun 13 2010 23:44:18, gcc: 4.1.2 20080704 (Red Hat 4.1.2-48)

  Seems stream 0 codec frame rate differs from container frame rate : 59.94 (60000/1001) -> 29.97 (30000/1001)

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'FILENAME.mp4':
  
    Duration: 00:03:36.36, start: 0.000000, bitrate: 1305 kb/s
  
      Stream #0.0(eng): Video: h264, yuv420p, 640x428, 29.97 tbr, 29.97 tbn, 59.94 tbc
  
      Stream #0.1(eng): Audio: aac, 48000 Hz, stereo, s16
  
  Output #0, image2, to 'FILENAME.jpg':
  
      Stream #0.0(eng): Video: mjpeg, yuvj420p, 640x428, q=2-31, 200 kb/s, 90k tbn, 29.97 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  Press [q] to stop encoding
  
  [h264 @ 0x307f6b0]brainfart cropping not supported, this could look slightly wrong ...
  
  [h264 @ 0x307f6b0]AVC: Consumed only 14978 bytes instead of 14984
  
  [h264 @ 0x307f6b0]AVC: Consumed only 1147 bytes instead of 1153
  
  [h264 @ 0x307f6b0]Missing reference picture
  
  [h264 @ 0x307f6b0]AVC: Consumed only 1947 bytes instead of 1953
  
  [h264 @ 0x307f6b0]Missing reference picture
  
  [h264 @ 0x307f6b0]AVC: Consumed only 1870 bytes instead of 1876
  
  [h264 @ 0x307f6b0]Missing reference picture
  
      Last message repeated 1 times
  
  [h264 @ 0x307f6b0]AVC: Consumed only 810 bytes instead of 816
  
  [h264 @ 0x307f6b0]Missing reference picture
  
      Last message repeated 1 times
  
  [h264 @ 0x307f6b0]AVC: Consumed only 955 bytes instead of 961
  
  [h264 @ 0x307f6b0]Missing reference picture
  
      Last message repeated 1 times
  
  [h264 @ 0x307f6b0]AVC: Consumed only 1036 bytes instead of 1042
  
  [h264 @ 0x307f6b0]Missing reference picture
  
      Last message repeated 1 times
  
  [h264 @ 0x307f6b0]AVC: Consumed only 998 bytes instead of 1004
  
  [h264 @ 0x307f6b0]Missing reference picture
  
  frame=    1 fps=  0 q=3.3 Lsize=      -0kB time=0.03 bitrate=  -5.3kbits/s
  
  video:14kB audio:0kB global headers:0kB muxing overhead -100.149568%

• Drupal 7 audioconverter module failed - libavcodec52 - which codec for Debian squeeze ?

  7 décembre 2012, par Meggy

  I am using the audioconverter module with the audiorecorderfield module in Drupal 7. Though it was working previously, I just recently noticed that the audioconverter module has stopped converting wav files to mp3. Here's the error in my logs ;

  MESSAGE: executing: /usr/bin/ffmpeg -i /var/aegir/platforms/drupal-7.16/sites/default/files/1354856044.wav /var/aegir/platforms/drupal-7.16/sites/default/files/1354856044.wav.mp3
  
  
  
  MESSAGE: Audio conversion failed. FFMPEG reported the following output: 
  
  
  
  FFmpeg version SVN-r0.5.9-4:0.5.9-1, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  
    configuration: --extra-version=4:0.5.9-1 --prefix=/usr --enable-avfilter --enable-avfilter-lavf --enable-vdpau --enable-bzlib --enable-libdirac --enable-libgsm --enable-libopenjpeg --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib --disable-stripping --disable-vhook --enable-runtime-cpudetect --enable-gpl --enable-postproc --enable-swscale --enable-x11grab --enable-libfaad --enable-libdc1394 --enable-shared --disable-static
  
    libavutil     49.15. 0 / 49.15. 0
  
    libavcodec    52.20. 1 / 52.20. 1
  
    libavformat   52.31. 0 / 52.31. 0
  
    libavdevice   52. 1. 0 / 52. 1. 0
  
    libavfilter    0. 4. 0 /  0. 4. 0
  
    libswscale     0. 7. 1 /  0. 7. 1
  
    libpostproc   51. 2. 0 / 51. 2. 0
  
  built on Jun 10 2012 10:30:14, gcc: 4.4.5
  
  Input #0, wav, from '/var/aegir/platforms/drupal-7.16/sites/default/files/1354857172.wav':
  
  Duration: 00:00:27.50, bitrate: 178 kb/s
  
  Stream #0.0: Audio: adpcm_ima_wav, 44100 Hz, mono, s16, 178 kb/s
  
  Output #0, mp3, to '/var/aegir/platforms/drupal-7.16/sites/default/files/1354857172.wav.mp3':
  
  Stream #0.0: Audio: 0x0000, 44100 Hz, mono, s16, 64 kb/s
  
  Stream mapping:
  
  Stream #0.0 -> #0.0
  
  Unsupported codec for output stream #0.0
  
  
  
  SEVERITY: error
  
  
  
  MESSAGE: converted file is an empty file.

  It seems similar to the fixed issue posted by tinny here http://drupal.org/node/1818308 but I have libavcodec52 installed and I'm still getting these errors.

  I can see the wav file is created by the audiorecorder module but the audioconverter module is failing on the conversion.

  Does anyone know which codec I should use in Debian 6 Squeeze ?