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• Building FFMPEG library for iOS5.1 ARMv7

  25 octobre 2012, par Jimmy

  I'm trying to use the FFMPEG library in an XCode 4.5.1 project. And I'm trying to build it for ARMv7

  But I'm running into some major issues, I'm hoping that someone can walk me through how to do it ? I feel a little sketched out reading material thats a couple months old. I'm not aware of the changes.

  New Update (after a lot of time)

  I want to help everyone out that is having this problem because its so frustrating. heres how you do it. I've pasted the configuration stage. This is my ./configure

  ./configure --disable-doc --disable-ffmpeg --disable-ffplay --disable-ffserver --enable-cross-compile --arch=arm --target-os=darwin
  
     --cc=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/llvm-gcc-4.2/bin/arm-apple-darwin10-llvm-gcc-4.2
  
     --as='gas-preprocessor/gas-preprocessor.pl /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/llvm-gcc-4.2/bin/arm-apple-darwin10-llvm-gcc-4.2'
  
     --sysroot=/applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk
  
     --cpu=cortex-a8
  
     --extra-ldflags='-isysroot /applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk'
  
     --enable-pic
  
     --disable-bzlib --disable-gpl --disable-shared --enable-static --disable-mmx --disable-debug --disable-neon
  
     --extra-cflags='-pipe -Os -gdwarf-2 -isysroot /applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk -m${thumb_opt:-no-thumb} -mthumb-interwork'

  This ended up working for me. I had the following problems.

  • I had to download ( https://github.com/yuvi/gas-preprocessor ) copy the file gas-preprocessor.pl at /usr/local/bin. Set permissions to read write (777)
  • Make sure I'm using the right GCC compiler : /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/usr/llvm-gcc-4.2/bin/arm-apple-darwin10-llvm-gcc-4.2
  • Make sure I'm using the right SDK : /applications/xcode.app/contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS5.1.sdk
  • —extra-cflags="-arch armv7" causes bugs in the configure. take it out. This was causing my gcc compile errors. (specifically this one : error : unrecognized command line option “-arch”.)

  I'll let you guys know how much further I get.

• What ffmpeg command to use to convert a list of unsigned integers into an audio file ?

  21 mars 2019, par John

  I have a file that contains a list of about forty thousand integers that are space delimited, with each integer between the value of 0 and 255. It is this file here :

  https://github.com/johnlai2004/sound-project/blob/master/integers.txt

  If you connect a speaker to an ESP32 breakout board, then run this list of integers through the digital to analog converter at a frequency of 24kHz, you will hear the sentence, "That’s not the post that you missed."

  What I want to know is how do you use FFMPEG to convert this list of integers into a sound file that other computer can play to hear the same phrase ? I tried this command :

  ffmpeg -f u8 -ac 1 -ar 24000 -i integers.txt -y audio.wav

  But my audio.wav just sounds like white noise. I tried a few other values for -f and for -ar, but all I hear are different frequencies of white noise and maybe some extra buzzing.

  Is it possible to use ffmpeg to translate my list of integers into an audio file for other computers to play ? If so, what’s the correct ffmpeg command to do this ?

  OTHER NOTES

  If it helps, this is the sketch file that I upload to an ESP32 if I want to hear the audio :

  https://github.com/johnlai2004/sound-project/blob/master/play-audio.ino

  In short, the file looks like this :

  #define speakerPin 25                          //The pins to output audio on. (9,10 on UNO,Nano)
  
  #define bufferTotal 1347
  
  #define buffSize 32
  
  
  
  byte buffer[bufferTotal][buffSize];
  
  int buffItemN = 0;
  
  int bufferN = 0;
  
  
  
  hw_timer_t * timer = NULL;
  
  portMUX_TYPE timerMux = portMUX_INITIALIZER_UNLOCKED;
  
  
  
  void IRAM_ATTR onTimer() {
  
    portENTER_CRITICAL_ISR(&timerMux);
  
  
  
  
  
    byte v = buffer[bufferN][buffItemN];
  
    dacWrite(speakerPin,v);
  
  
  
    buffItemN++;
  
  
  
    if(buffItemN >= buffSize){                                      //If the buffer is empty, do the following
  
      buffItemN = 0;                                              //Reset the sample count
  
      bufferN++;
  
      if(bufferN >= bufferTotal)
  
        bufferN = 0;
  
    }
  
  
  
    portEXIT_CRITICAL_ISR(&timerMux);
  
  
  
  }
  
  
  
  void setup() {      
  
  
  
  /* buffer records */
  
  buffer[0][0]=88;  // I split the long list of integers and load it into a 2D array
  
  buffer[0][1]=88;
  
  buffer[0][2]=86;
  
  buffer[0][3]=85;
  
  //etc....
  
  buffer[1346][28]=94;
  
  buffer[1346][29]=92;
  
  buffer[1346][30]=92;
  
  buffer[1346][31]=95;
  
  
  
  
  
  /* end buffer records */
  
  
  
    timer = timerBegin(0, 80, true);
  
    timerAttachInterrupt(timer, &onTimer, true);
  
    timerAlarmWrite(timer, 41, true);
  
    timerAlarmEnable(timer);
  
  
  
  }
  
  
  
  void loop() {
  
  
  
  }

  The buffer... is the list of integers found in the integers.txt file.

• ffmpeg - when scaling, how to keep shapes of people's heads

  19 janvier 2017, par Dave

  Ok, I’m quite familiar with FFMPEG utility in general, and have used it for
  years to cut short snippets from videos, etc. But it’s only in the last
  month that and I decided to learn to use it to transcode with video-filters
  etc. (Before that, I was using other tools such as ’Handbrake’ and ’FreeMake’
  and VLC, etc.)

  For my ffmpeg transcodes, my target output resolution will always be constant, from one transcode run to the next. But the resolution and display aspect-ratio of the input file, from one transcode run to the next, will vary...could be almost any values.
  The input files will never already have black-bars when displayed.

  So, the relevant portion [ i.e. the video-filter(s) part) of my cmd line ] presently is as follows :

  ffmpeg ... -vf "scale=720:406,setsar=1,pad=720:506:0:40:Black" ...

  Also note : I do NOT use the "-aspect" option in the cmd-line. (Maybe I’ll
  need to (???) to solve my issue, but I’m unsure about how that interacts
  with scaling.)

  ( EDIT : Oh, I happen to have chosen that resolution value of 720x406, for
  the image-area (i.e. inside the top/bottom black bars) because it
  has an aspect ratio of 16:9 (Of course, 16:9 ratio is common these days. )

  My cmd always executes cleanly and produces an output file (a WebM, tho I doubt
  that container types and/or vcodec choices matter at all to scaling algorithm issues).

  So the issue/problem that I’m trying to solve is how to prevent any stretching
  in either direction. In other words, a round soccer ball in the input file
  must yield a round ball in the output file ! (NOT oval-shaped in either axis).

  ( Edit #2 : Oh, I forgot to mention that I’m not have the same amount of stretching from one ffmpeg output file to the next. Sometimes there is
  no stretch in my output file, and with some other input file, the
  people are too tall in the output, and some other output file will have
  people are too wide. I’m assuming
  there is some single cmd that will always work for each randomly sized
  input file, WITHOUT having to resort to examining meta-data of each
  input and then having to adjust portions of the needed ffmpeg cmd.
  I assume this because I have used a tool called "FreeMake" that needs
  no such adjustment. When you do a ’scale’ with that program, it asks
  you to choose one of four adjustment-algorithms labeled "original"
  "stretched", "zoom..." and "auto". If I recall correctly, it was the
  "auto" choice that prevented any stretching.)

  The goal of that last filter (i.e. the "pad=720:506:0:40:Black" phrase) is to
  add a black bar of 40 pixels to the top and 60 pixels to the bottom.
  (That filter IS producing the black-bands, as desired. I mention it,
  because I’m unsure whether it could be having any effect on the altered
  shape of the ’round soccer ball’). If the "pad" filter IS part of the
  issue, then maybe I’ll need to make multiple ffmpeg cmds to achieve
  my overall goal (!?!?). [I’d LIKE to be able to do everything in just
  one ffmpeg cmd, as shown.]

  OK ?

  So are there any image-processing and ffmpeg gurus out there that
  know how to fix my problem ?

  TIA...

  Dave