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• when webm extracts aac, the duration is inconsistent

  25 juillet 2019, par Black-Hole

  When I try to extract aac from webm, there will be inconsistencies in duration. aac is ten minutes less. Different webm videos, the gap is not the same.

  webm video is generated by chrome extension chrome.tabCapture.capture

  code :

  chrome.tabCapture.capture({
  
    video: true,
  
    audio: true,
  
    videoConstraints: {
  
      mandatory: {
  
        minWidth: 1920,
  
        minHeight: 1080,
  
        maxWidth: 1920,
  
        maxHeight: 1080,
  
        maxFrameRate: 30,
  
        minFrameRate: 30,
  
      }
  
    }
  
  })

  The above code will return a stream, I will use JS’s MediaRecorder method to process this stream, and finally save it as a webm file.

  code :

  new MediaRecorder(stream, {
  
    audioBitsPerSecond: 128000,
  
    videoBitsPerSecond: 2500000,
  
    mimeType: 'video/webm;codecs=vp9'
  
  })

  If you don’t know the meaning of the above code, it doesn’t matter, I will explain the main information :

  1. width : 1920
  2. height : 1080
  3. FPS : 30
  4. audioBits : 128000
  5. videoBits : 2500000
  6. mimeType : video/webm;codecs=vp9

  I tried a lot of methods, like the following :

  # 1
  
  ffmpeg -i ./source.webm -y -fflags +genpts -max_muxing_queue_size 99999 -r 15 -crf 30 -filter:v crop=750:560:0:0 ./x.mp4
  
  ffmpeg -i ./x.mp4 -y -vn -acodec libfdk_aac -b:a 200k ./x.aac
  
  
  
  # 2
  
  ffmpeg -i ./source.webm -y -vn -acodec libfdk_aac -b:a 200k ./x.aac
  
  
  
  # 3
  
  ffmpeg -i ./source.webm -y -vn -acodec libfdk_aac -b:a 200k -map 0 ./x.aac
  
  
  
  # 4
  
  ffmpeg -i ./source.webm -y -max_muxing_queue_size 99999 -r 15 -crf 30 -filter:v crop=750:560:0:0 ./x.mp4
  
  ffmpeg -i ./source.webm -y -vn -acodec aac -b:a 200k ./x.aac
  
  
  
  # etc.

  But without exception, all failed. I have been plagued by this problem for 4 days.

  webm file download url : https://drive.google.com/file/d/1m4fC1hU-tXFPOZayrYCs-yteSTxw_TaW/view?usp=sharing

• Fluent FFmpeg Corrupting MP3s

  6 décembre 2019, par Joseph Horsch

  I am using fluent-ffmpeg and libmp3lame (https://github.com/fluent-ffmpeg/node-fluent-ffmpeg) to convert file uploads to mp3 and ultimately upload to S3. The files become corrupted intermittently in the conversion process (I suspect).

  I am unable to reproduce this scenario myself. Likewise, I cannot request the original source audio files from my active users, so testing is difficult.

  When I download the corrupt mp3s locally to inspect them I noticed they will not play in Finder or iTunes. Interestingly enough, I can open, play, and reconvert them in Audacity.

  I have run the command line tool mp3val and it outputs these results :

  Analyzing file "5de58556d770a800168f86f2-bad.mp3"...
  
  WARNING: "~/Downloads/5de58556d770a800168f86f2-bad.mp3" (offset 0xa): MPEG stream error, resynchronized successfully
  
  WARNING: "~/Downloads/5de58556d770a800168f86f2-bad.mp3": VBR detected, but no VBR header is present. Seeking may not work properly.
  
  INFO: "~/Downloads/5de58556d770a800168f86f2-bad.mp3": 3749 MPEG frames (MPEG 1 Layer III), +ID3v2, no VBR header
  
  Done!

  My converion code looks like this :

  ffmpeg()
  
      .input(tempUploadPath)
  
      .format('mp3')
  
      .audioCodec('libmp3lame')
  
      .audioQuality(0)
  
      .pipe(uploadFromStream(audioPath))
  
      .on('close', () => logger.info('passThrough-close'))
  
      .on('finish', () => {
  
        removeTempFile(tempUploadPath)
  
          .then(() => {
  
            logger.info(`Removed temp file ${tempUploadPath}`);
  
            resolve(audioPath);
  
          })
  
          .catch((err) => {
  
            logger.error('Could not remove template file.', err);
  
            resolve(audioPath);
  
          });
  
      })
  
      .on('error', (err) => {
  
        logger.error(`Could not convert audio. ${JSON.stringify(err)}`);
  
        removeTempFile(tempUploadPath)
  
          .then(() => reject())
  
          .catch((rmErr) => reject(rmErr));
  
      });

  Here is a link to one of the corrupted output files :
  https://drive.google.com/open?id=16khdEogaPXeNEM9MuChd5DsNHC3NY0DZ

• SNAP : Simulation and Neuroscience Application Platform [closed]

  19 avril 2024, par S_S

  Is there any documentation/help manual on how to use SNAP (Simulation and Neuroscience Application Platform)1.

  



  I wanted to run the Motor Imagery sample scenario with a .avi file for the stimulus instead of the image. How can that be done ?

  



  The following error is obtained when using the AlphaCalibration scenario which gives code to play an avi file.Any help appreciated

  



  :movies:ffmpeg(warning): parser not found for codec indeo4, packets or times may be invalid.
:movies:ffmpeg(warning): max_analyze_duration 5000000 reached at 5000000
:movies(error): Could not open /e/BCI_Feb2014/SNAP-master/src/studies/SampleStudy/bird.avi
:audio(error): Cannot open file: /e/BCI_Feb2014/SNAP-master/src/studies/SampleStudy/bird.avi
:audio(error): Could not open audio /e/BCI_Feb2014/SNAP-master/src/studies/SampleStudy/bird.avi
:movies:ffmpeg(warning): parser not found for codec indeo4, packets or times may be invalid.
:movies:ffmpeg(warning): max_analyze_duration 5000000 reached at 5000000
:movies(error): Could not open /e/BCI_Feb2014/SNAP-master/src/studies/SampleStudy/bird.avi
:gobj(error): Texture "/e/BCI_Feb2014/SNAP-master/src/studies/SampleStudy/bird.avi" exists but cannot be read.
Traceback (most recent call last):
  File "E:\BCI_Feb2014\SNAP-master\src\framework\latentmodule.py", line 458, in _run_wrap
    self.run()
  File "modules\BCI\AlphaCalibration.py", line 30, in run
Exception during run():
    m = self.movie(self.moviefile, block=False, scale=[0.7,0.4],aspect=1.125,contentoffset=[0,0],volume=0.3,timeoffset=self.begintime+t*self.awake_duration,looping=True)
Could not load texture: bird.avi
  File "E:\BCI_Feb2014\SNAP-master\src\framework\basicstimuli.py", line 348, in movie
    tex = self._engine.base.loader.loadTexture(filename)
  File "E:\BCI_Feb2014\Panda3D-1.8.0\direct\showbase\Loader.py", line 554, in loadTexture
    raise IOError, message
IOError: Could not load texture: bird.avi