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• Amazon Alexa Audio Encoding- Few audios are not playing [closed]

  3 mars 2023, par Vijayanath Viswanathan

  I am encoding audio for Alexa audio using ffmpeg like below,

  



  ffmpeg -i  -ac 2 -codec:a libmp3lame -b:a 48k -ar 16000 


  



  The problem is few of the audios are playing properly but few are not. I am using same Project Rate and Quality (Project Rate 16000 and Quality to 48 kbps) for all audios which needs to be converted. Anybody knows is there any basic quality for source.mp3 to encode to Project Rate 16000 and Quality to 48 kbps ?

  



  The response I am getting from alexa for faulty file is, "There is a problem with skill response".

  


• Writing a series of images into a video file using libavcodec (ffmpeg)

  19 novembre 2013, par user2978372

  Requirements :

  I have a bunch of images (to be more specific they are 1024x768, 24bpp RGB PNG files) that I want to encode into a video files.

  And I need to use 'libavcodec' library, not 'ffmpeg' tool. (well I know they are basically same in the origin, I am emphasizing because someone may answer to use 'ffmpeg' tool, but that's not a solution what I am looking for)

  I am using h264 encoder.

  Target :
  A high quality video with equal resolution (1024 x 768), YUV420P
  each image has a duration of 1 second.
  24 fps

  Problems :
  i've tried with many different (but same resolution and bits) png images, and all have failed to output a good video.

  For some series of images, only the frames of first second was shown in a good shape, but the remaining frames was distorted and color changed (lighter).

  For some series of images, it seemed the images were zoomed-in and distorted again.

  and etc.

  Question :
  I am a total AV newbie and I need someone to verify my steps for encoding. I am total AV newbie.

  1) av_register_all()

  2) avcodec_register_all()

  3) avcodec_find_encoder()

  4) avcodec_alloc_context3()

  5) sets codec configuraton to context.

  6) avcodec_open2()

  7) opens a output file using fopen_s()

  8)

  for(int second=1; second<=10; ++seconds)
  
  {
  
  
  
    Read a image from local using Gdiplus
  
  
  
    Create a gdiplus bitmap and draw the image onto this bitmap
  
  
  
    Get the raw byte data using LockBits
  
  
  
    Transfer this RGB raw byte into YUV420 frame using 'swscontext', 'sws_scale'
  
  
  
    for(int f=0; f<24; ++f)
  
    {
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;
  
      pkt.size = 0;
  
  
  
      pFrame->pts = f;
  
      ret = avcodec_encode_video2(pContext, &pkt, pFrame, &got_output);
  
  
  
      if(got_output)
  
      {
  
          fwrite(pkt.data, 1, pkt.size, outputFile);
  
          av_free_packet(&pkt);
  
      }
  
    }
  
  }
  
  
  
  /* get the delayed frames */
  
  for (got_output = 1; got_output; i++) {
  
      fflush(stdout);
  
  
  
      ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
  
      if (ret < 0) {
  
          fprintf(stderr, "Error encoding frame\n");
  
          exit(1);
  
      }
  
  
  
      if (got_output) {
  
          printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
          fwrite(pkt.data, 1, pkt.size, f);
  
          av_free_packet(&pkt);
  
      }
  
  }
  
  
  
  close everything required

  I am sure that I misunderstood some steps using ffmpeg api. The above pseudo codes are based on the 'encoding' example of ffmpeg. which part am I doing wrong ? please can someone help me ?

  p.s sorry about broken english. english is not my natvie language. I tried my best =P

• Piping a series of node JS buffers to ffmpeg

  27 octobre 2018, par Julian Weimer

  I’m generating a series of frames and save them as buffers in a Redis database. Currently, I’m struggling to find out how I pipe them into FFmpeg in order to create a video. The goal of using this approach in favor of saving the frames on disk is to increase the performance. The length of a generated video won’t exceed 3 minutes.

  In the following function, I’m trying to collect all the frames from Redis, concatenate them together and save them into a temporary buffer using stream-buffers. Then I’m trying to use fluent-ffmpeg to finally output the video.

  let renderVideo = async () => {
  
    let data
  
  
  
    let frames = []
  
  
  
    for (let i = 0; i <= readyFrames.length - 1; i++) {
  
      data = await cache.get(`frame_${i}`)
  
      frames.push(data)
  
    }
  
  
  
    let allFramesTogether = Buffer.concat(frames) // Does
  
    tempReadableBuffer.put(allFramesTogether)     // not
  
    ffmpeg().input(tempReadableBuffer)            // work
  
  
  
    ffmpeg()
  
      .outputOptions(['-f image2pipe', '-pix_fmt yuv420p'])
  
      .videoCodec('libx264')
  
      .size(`${dimensions.width}x${dimensions.height}`)
  
      .format('mp4')
  
      .fps(FPS)
  
      .on('progress', function(progress) {
  
        console.log('Processing: ' + progress.percent + '% done')
  
      })
  
      .on('end', function() {
  
        console.log('Processing finished !')
  
      })
  
      .on('stderr', function(stderrLine) {
  
        console.log('Stderr output: ' + stderrLine)
  
      })
  
      .on('error', function(err, stdout, stderr) {
  
        console.log('Cannot process video: ' + err.message)
  
      })
  
      .save('test.mp4')
  
  }