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• Revision 36914 : On affiche si ffmpeg-php est correctement installé avec quelques ...

  4 avril 2010, par kent1@… — Log

  On affiche si ffmpeg-php est correctement installé avec quelques information sur son installation
  les options de taille et de audiorate ne marchent pas dans les pressets de ffmpeg ... on doit les laisser dans la ligne de commande du script
  On ajoute deux filtres pour les codecs issus des métadatas des flv

• Visualizing Call Graphs Using Gephi

  1er septembre 2014, par Multimedia Mike — General

  When I was at university studying computer science, I took a basic chemistry course. During an accompanying lab, the teaching assistant chatted me up and asked about my major. He then said, “Computer science ? Well, that’s just typing stuff, right ?”

  My impulsive retort : “Sure, and chemistry is just about mixing together liquids and coming up with different colored liquids, as seen on the cover of my high school chemistry textbook, right ?”

  
  
  

  In fact, pure computer science has precious little to do with typing (as is joked in CS circles, computer science is about computers in the same way that astronomy is about telescopes). However, people who study computer science often pursue careers as programmers, or to put it in fancier professional language, software engineers.

  So, what’s a software engineer’s job ? Isn’t it just typing ? That’s where I’ve been going with this overly long setup. After thinking about it for long enough, I like to say that a software engineer’s trade is managing complexity.

  A few years ago, I discovered Gephi, an open source tool for graph and data visualization. It looked neat but I didn’t have much use for it at the time. Recently, however, I was trying to get a better handle on a large codebase. I.e., I was trying to manage the project’s complexity. And then I thought of Gephi again.

  Prior Work
  One way to get a grip on a large C codebase is to instrument it for profiling and extract details from the profiler. On Linux systems, this means compiling and linking the code using the -pg flag. After running the executable, there will be a gmon.out file which is post-processed using the gprof command.

  GNU software development tools have a reputation for being rather powerful and flexible, but also extremely raw. This first hit home when I was learning how to use the GNU tool for code coverage — gcov — and the way it outputs very raw data that you need to massage with other tools in order to get really useful intelligence.

  And so it is with gprof output. The output gives you a list of functions sorted by the amount of processing time spent in each. Then it gives you a flattened call tree. This is arranged as “during the profiled executions, function c was called by functions a and b and called functions d, e, and f ; function d was called by function c and called functions g and h”.

  How can this call tree data be represented in a more instructive manner that is easier to navigate ? My first impulse (and I don’t think I’m alone in this) is to convert the gprof call tree into a representation suitable for interpretation by Graphviz. Unfortunately, doing so tends to generate some enormous and unwieldy static images.

  Feeding gprof Data To Gephi
  I learned of Gephi a few years ago and recalled it when I developed an interest in gaining better perspective on a large base of alien C code. To understand what this codebase is doing for a particular use case, instrument it with gprof, gather execution data, and then study the code paths.

  How could I feed the gprof data into Gephi ? Gephi supports numerous graphing formats including an XML-based format named GEXF.

  Thus, the challenge becomes converting gprof output to GEXF.

  Which I did.

  Demonstration
  I have been absent from FFmpeg development for a long time, which is a pity because a lot of interesting development has occurred over the last 2-3 years after a troubling period of stagnation. I know that 2 big video codec developments have been HEVC (next in the line of MPEG codecs) and VP9 (heir to VP8’s throne). FFmpeg implements them both now.

  I decided I wanted to study the code flow of VP9. So I got the latest FFmpeg code from git and built it using the options "--extra-cflags=-pg --extra-ldflags=-pg". Annoyingly, I also needed to specify "--disable-asm" because gcc complains of some register allocation snafus when compiling inline ASM in profiling mode (and this is on x86_64). No matter ; ASM isn’t necessary for understanding overall code flow.

  After compiling, the binary ‘ffmpeg_g’ will have symbols and be instrumented for profiling. I grabbed a sample from this VP9 test vector set and went to work.

  ./ffmpeg_g -i vp90-2-00-quantizer-00.webm -f null /dev/null
  gprof ./ffmpeg_g > vp9decode.txt
  convert-gprof-to-gexf.py vp9decode.txt > /bigdisk/vp9decode.gexf
  

  Gephi loads vp9decode.gexf with no problem. Using Gephi, however, can be a bit challenging if one is not versed in any data exploration jargon. I recommend this Gephi getting starting guide in slide deck form. Here’s what the default graph looks like :

  
  
  

  Not very pretty or helpful. BTW, that beefy arrow running from mid-top to lower-right is the call from decode_coeffs_b -> iwht_iwht_4x4_add_c. There were 18774 from the former to the latter in this execution. Right now, the edge thicknesses correlate to number of calls between the nodes, which I’m not sure is the best representation.

  Following the tutorial slide deck, I at least learned how to enable the node labels (function symbols in this case) and apply a layout algorithm. The tutorial shows the force atlas layout. Here’s what the node neighborhood looks like for probing file type :

  
  
  

  Okay, so that’s not especially surprising– avprobe_input_format3 calls all of the *_probe functions in order to automatically determine input type. Let’s find that decode_coeffs_b function and see what its neighborhood looks like :

  
  
  

  That’s not very useful. Perhaps another algorithm might help. I select the Fruchterman–Reingold algorithm instead and get a slightly more coherent representation of the decoding node neighborhood :

  
  
  

  Further Work
  Obviously, I’m just getting started with this data exploration topic. One thing I would really appreciate in such a tool is the ability to interactively travel the graph since that’s what I’m really hoping to get out of this experiment– watching the code flows.

  Perhaps someone else can find better use cases for visualizing call graph data. Thus, I have published the source code for this tool at Github.

• 'C' program to pipeout audio file to FFMPEG and generate Video file

  9 mai 2017, par soflow

  I am attempting to write a short ’C’ program which reads in an Audio file using FFMPEG, processes that file using a ’C’ program, and then outputs a file via FFMEPG, which combines the new, modified audio together with a Video representation using the FFMPEG showwaves filter.

  At present the program attempts to do the following :-

  i) Read in an audio file, using pipein thorugh FFMPEG
  ii) Process the audio file using a portion of the ’C’ program
  iii) Pipeout the modified audio to FFMPEG, and generate a file using the ’showwaves’ filter in FFMEPG to create an MP4 file with audio and video.

  The following code run form the ommand line in FFMPEG generates the Audio/Video MP4 I want to create :-

  ffmpeg -y -f s16le -ar 44100 -ac 1 -i 12345678.wav  -i 12345678.wav  -filter_complex  "[0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  12345678.mp4

  "

  This code generates a processed audio file, and outputs it to a .wav file as required :-

  #include 
  
  #include 
  
  #include 
  
  
  
  void main()
  
  {
  
  // Launch two instances of FFmpeg, one to read the original WAV
  
  // file and another to write the modified WAV file. In each case,
  
  // data passes between this program and FFmpeg through a pipe.
  
  FILE *pipein;
  
  FILE *pipeout;
  
  pipein  = popen("ffmpeg -i 12345678.wav -f s16le -ac 1 -", "r");
  
  pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i - out.wav", "w");
  
  
  
  // Read, modify and write one sample at a time
  
  int16_t sample;
  
  int count, n=0;
  
  while(1)
  
  {
  
      count = fread(&sample, 2, 1, pipein); // read one 2-byte sample
  
      if (count != 1) break;
  
      ++n;
  
      sample = sample * sin(n * 5.0 * 2*M_PI / 44100.0);
  
      fwrite(&sample, 2, 1, pipeout);
  
  }
  
  
  
  // Close input and output pipes
  
  pclose(pipein);    
  
  pclose(pipeout);
  
  }

  (This code borrowed from ted Burke’s excellent post here)

  I have made an attempt as shown below, but this is not working :-

  #include 
  
  #include 
  
  #include 
  
  
  
  void main()
  
  {
  
  // Launch two instances of FFmpeg, one to read the original WAV
  
  // file and another to write the modified WAV file. In each case,
  
  // data passes between this program and FFmpeg through a pipe.
  
  FILE *pipein;
  
  FILE *pipeout;
  
  pipein  = popen("ffmpeg -i 12345678.wav -f s16le -ac 1 -", "r");
  
  pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i 12345678.wav  -i 
  
  12345678.wav  -filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  ", "w");
  
  
  
  
  
  // Read, modify and write one sample at a time
  
  int16_t sample;
  
  int count, n=0;
  
  while(1)
  
  {
  
      count = fread(&sample, 2, 1, pipein); // read one 2-byte sample
  
      if (count != 1) break;
  
      ++n;
  
      sample = sample * sin(n * 5.0 * 2*M_PI / 44100.0);
  
      fwrite(&sample, 2, 1, pipeout);
  
  }
  
  
  
  // Close input and output pipes
  
  pclose(pipein);    
  
  pclose(pipeout);
  
  }    

  Ideally someone can suggest an improved version of the pipeout command above - alternately another process to achieve this would be interesting

  * EDIT *

  Thanks to @Mulvya, the revised pipeout line is now :-

  pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -filter_complex  "[0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  12345678.mp4

  ", "w") ;

  On compiling with gcc I get the following error messages :-

  avtovid2.c: In function \u2018main\u2019:
  
  
  
  wavtovid2.c:13:83: error: expected \u2018]\u2019 before \u2018:\u2019 
  
  token
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:86: error: expected \u2018)\u2019 before 
  
  \u2018showwaves\u2019
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:98: error: invalid suffix "x720" on integer constant
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:153: warning: missing terminating " character
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:86: error: missing terminating " character
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:14:6: warning: missing terminating " character
  
   ", "w");
  
    ^
  
  wavtovid2.c:14:1: error: missing terminating " character
  
   ", "w");
  
   ^
  
  wavtovid2.c:13:21: warning: passing argument 1 of \u2018popen\u2019 makes 
  
  pointer from integer without a cast
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
                   ^
  
  In file included from wavtovid2.c:1:0:
  
  /usr/include/stdio.h:872:14: note: expected \u2018const char *\u2019 but 
  
  argument is of type \u2018char\u2019
  
   extern FILE *popen (const char *__command, const char *__modes) __wur;
  
            ^
  
  wavtovid2.c:13:15: error: too few arguments to function \u2018popen\u2019
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
             ^ 
  
  In file included from wavtovid2.c:1:0:
  
  /usr/include/stdio.h:872:14: note: declared here
  
   extern FILE *popen (const char *__command, const char *__modes) __wur;
  
            ^
  
  wavtovid2.c:32:1: error: expected \u2018;\u2019 before \u2018}\u2019 
  
  token
  
   }