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• Is there any way to concatinate multiple video and audio streams with offset ?

  17 avril 2019, par Demchenko Oleg

  I am sory for my english, it is not my mother language. My issue related to ffmpeg concatenation of audio and video streams. There are multiple audio and video streams which were recorded by online chat. All of them have start and end time points. If user turned off a micro or camera then audio and video streams wouldn’t be matched. How can I align all streams in one time series ? Can I add some white noise to separate the two videos ? Similar with audio.

• How can we reduce the size of audio file after uploading ?

  8 novembre 2019, par Arjun Pujari

  I have used this command in the terminal to install the package : composer require pbmedia/laravel-ffmpeg. The package is successfully downloaded, but I don’t know how to use it. I don’t even know if this package can also reduce the audio file size or not.

  Anyone know any other library or package ?

      
  
          <form action="{{route('upload')}}" method="post" enctype="multipart/form-data">
  
              Select Audio to upload:
  
              <input type="file" />
  
              <input type="submit" value="upload MP3" />
  
          </form>
  
      
  
  
  
  
  
  &lt;?php

  Here is my controller. Write basic code for save file :

  namespace App\Http\Controllers;
  
  
  
  use Illuminate\Http\Request;
  
  use Pbmedia\LaravelFFMpeg\FFMpeg;
  
  
  
  class FileCompress extends Controller
  
  {   
  
      public function compressFile(Request $request)
  
      {
  
            $uploadFileName = mt_rand().time(). '.' . $file->getClientOriginalExtension();
  
            $filetype = substr($file->getClientMimeType(), 0, strpos($file->getClientMimeType(), "/"));
  
  
  
          if($filetype == 'video'){
  
  
  
            $localpath =  public_path().'/videos/'.$uploadFileName;
  
           //code for video file compress.
  
          }else{
  
            //code for audio file compress.
  
          }
  
      }
  
  }

  But I need to reduce the audio file size when a file is uploaded or reduce the file size immediately after the file upload. How can i do that ?

• Understanding the VP8 Token Tree

  7 juin 2010, par Multimedia Mike — VP8

  I got tripped up on another part of the VP8 decoding process today. So I drew a picture to help myself understand it. Then I went back and read David Conrad’s comment on my last post regarding my difficulty understanding the VP8 spec and saw that he ran into the same problem. Since we both experienced the same hindrance in trying to sort out this matter, I thought I may as well publish the picture I drew.

  VP8 defines various trees for decoding different syntax elements. There is one tree for decoding the tokens and it is expressed in the VP8 spec as such :

  PLAIN TEXT

  C :

  1. const tree_index coef_tree [2 * (num_dct_tokens - 1)] =
  2. {
  3.  -dct_eob, 2,        /* eob = "0"  */
  4.   -DCT_0, 4,        /* 0  = "10" */
  5.   -DCT_1, 6,        /* 1  = "110" */
  6.    8, 12,
  7.    -DCT_2, 10,      /* 2  = "11100" */
  8.     -DCT_3, -DCT_4,    /* 3  = "111010", 4 = "111011" */
  9.    14, 16,
  10.     -dct_cat1, -dct_cat2, /* cat1 = "111100", cat2 = "111101" */
  11.    18, 20,
  12.     -dct_cat3, -dct_cat4, /* cat3 = "1111100", cat4 = "1111101" */
  13.     -dct_cat5, -dct_cat6 /* cat4 = "1111110", cat4 = "1111111" */
  14. } ;

  Here is what the table looks like when you make a tree out of it (click for full size image) :

  
  
  

  The catch is that it makes no sense for an end-of-block (EOB) token to follow a 0 token since EOB already indicates that the remainder of the coefficients should be 0 anyway. Thus, the spec states that, "decoding of certain DCT coefficients may skip the first branch, whose preceding coefficient is a DCT_0." I confess, I didn’t understand what "skip the first branch" meant until I drew the tree.

  
  
  

  For those wondering why it might be sub-optimal (clarity-wise) for a spec to simply regurgitate vast chunks of C code, this makes a decent case. As you can see, the spec makes certain assumptions about how a binary tree should be organized in a static array (node n points to elements n*2 and n*2+1 as its branches ; leaves are either negative or 0). This is the second method I have seen ; another piece of code (not the VP8 spec) had the nodes in the first half of the array and pointed to leaves in the second half. There must be other arrangements.