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• Converting DTS to AAC with ffmpeg shifts spoken audio to the right

  18 août 2018, par Giuseppe

  I am using ffmpeg to convert mkv movies to mp4, like so :

  $ ffmpeg -i source.mkv -c:v copy -c:a aac destination.mp4

  By doing this, the audio stream gets converted from the original DTS :

  Stream #0:1: Audio: dts (DTS), 48000 Hz, 5.1(side), fltp, 1536 kb/s (default)

  To AAC :

  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 394 kb/s (default)

  The resulting file plays just fine, except that the spoken audio (what I am assuming would be sent to the central channel in a 5.1 configuration) sounds clearly shifted to the right, when listening through the MacBook’s built-in speakers or my stereo headphones. Note that music and other sound effects appear unaffected, properly balanced. Also note that I have been able to reproduce this behavior with a variety of source files.

  Here’s ffmpeg’s banner :

  ffmpeg version 4.0.2 Copyright (c) 2000-2018 the FFmpeg developers
  
    built with Apple LLVM version 9.1.0 (clang-902.0.39.2)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/4.0.2 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-gpl --enable-libmp3lame --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-opencl --enable-videotoolbox --disable-lzma
  
    libavutil      56. 14.100 / 56. 14.100
  
    libavcodec     58. 18.100 / 58. 18.100
  
    libavformat    58. 12.100 / 58. 12.100
  
    libavdevice    58.  3.100 / 58.  3.100
  
    libavfilter     7. 16.100 /  7. 16.100
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  1.100 /  5.  1.100
  
    libswresample   3.  1.100 /  3.  1.100
  
    libpostproc    55.  1.100 / 55.  1.100

• do uploaded files to lambda persist ?

  24 novembre 2023, par Sam Leurs

  I have a node.js function where users kan upload a video file. The video file is uploaded to an S3-bucket. I have a lambda function which listens to the bucket for every upload. Every video that gets uploaded, gets converted via ffmpeg and stored into another bucket, and the original file is deleted.

  


  I messed around with ffmpeg in lambda, quiet difficult. I now have it working, but there is one problem : I'm using fluent-ffmpeg, and streaming data in and out from a bucket doesn't work.

  


  This is my code :

  


  promise...
ffmpeg().input(`https://s3.eu-central-1.amazonaws.com/mybucket.mywebsite.com/${key}`)
        .addInputOption('-analyzeduration 100M')
        .addInputOption('-probesize 100M')
        .toFormat('mp4')
        .addOutputOption("-preset veryfast")
        .addOutputOption("-movflags frag_keyframe+empty_moov")
        .addOutputOption("-crf 28")
        .output('/tmp/output.mp4')
        .on('error', (err, stdout, stderr) => {
            console.log(err);
            console.log('Stdout: %o', stdout);
            console.log('Stderr: %o', stderr);
            reject(err);
        })
        .on('end', () => {
          resolve();
        });
.run();


  


  As you can see, as an input file, I directly read the url of the video file. I wanted to create a readstream (I do this with images), but that didn't work.

  


  I temporary store the created video file as /tmp/output.mp4. After the code is done, I do this :

  


  await putObjectToS3(process.env.MY_NEW_BUCKET, newKey, '/tmp/output.mp4', mimeType);


  


  This works.

  


  My question now is : when the lambda function is done, what happens with the file in /tmp/output.mp4 ? Is it deleted, or is it stored somewhere until I deleted it. I don't need it anymore so I don't want to pay for the storage of it.

  


  Thanks in advance.

  


• Revision c8ed36432e : Non-uniform quantization experiment This framework allows lower quantization bi

  4 mars 2015, par Deb Mukherjee

  Changed Paths :
   Modify /configure

  
   Modify /vp9/common/vp9_blockd.h

  
   Modify /vp9/common/vp9_onyxc_int.h

  
   Modify /vp9/common/vp9_quant_common.c

  
   Modify /vp9/common/vp9_quant_common.h

  
   Modify /vp9/common/vp9_rtcd_defs.pl

  
   Modify /vp9/decoder/vp9_decodeframe.c

  
   Modify /vp9/decoder/vp9_detokenize.c

  
   Modify /vp9/encoder/vp9_block.h

  
   Modify /vp9/encoder/vp9_encodemb.c

  
   Modify /vp9/encoder/vp9_encodemb.h

  
   Modify /vp9/encoder/vp9_quantize.c

  
   Modify /vp9/encoder/vp9_quantize.h

  
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Non-uniform quantization experiment

  This framework allows lower quantization bins to be shrunk down or
  expanded to match closer the source distribution (assuming a generalized
  gaussian-like central peaky model for the coefficients) in an
  entropy-constrained sense. Specifically, the width of the bins 0-4 are
  modified as a factor of the nominal quantization step size and from 5
  onwards all bins become the same as the nominal quantization step size.
  Further, different bin width profiles as well as reconstruction values
  can be used based on the coefficient band as well as the quantization step
  size divided into 5 ranges.

  A small gain currently on derflr of about 0.16% is observed with the
  same paraemters for all q values.
  Optimizing the parameters based on qstep value is left as a TODO for now.

  Results on derflr with all expts on is +6.08% (up from 5.88%).

  Experiments are in progress to tune the parameters for different
  coefficient bands and quantization step ranges.

  Change-Id : I88429d8cb0777021bfbb689ef69b764eafb3a1de