title: youtube-dl DASH video and audio in highest quality without human intervention
body: <p>With youtube-dl I first look what video quality is available and then in second step I download highest possible quality (in this example <code>-f 137+140</code>). Youtube-dl will automatically merge audio and video stream (DASH format)</p>
  
  <p>How to automate that with shell script? With every URL, choose highest audio and video quality?</p>
  
  <pre><code>&gt; youtube-dl -F 'https://www.youtube.com/watch?v=VAdRBLyjLRQ&amp;feature=youtu.be&amp;t=8m14s'                              
  [youtube] Downloading login page                                                                                                      
  [youtube] Logging in                                                                                                                  
  [youtube] VAdRBLyjLRQ: Downloading webpage                                                                                            
  [youtube] VAdRBLyjLRQ: Downloading video info webpage                                                                                 
  [youtube] VAdRBLyjLRQ: Extracting video information                                                                                   
  [youtube] VAdRBLyjLRQ: Downloading DASH manifest                                                                                      
  [youtube] VAdRBLyjLRQ: Downloading DASH manifest                                                                                      
  [info] Available formats for VAdRBLyjLRQ:                                                                                             
  format code  extension  resolution note                                                                                               
  249          webm       audio only DASH audio , opus @ 50k                                                                            
  250          webm       audio only DASH audio , opus @ 70k                                                                            
  251          webm       audio only DASH audio , opus @160k                                                                            
  171          webm       audio only DASH audio  117k , vorbis@128k (44100Hz), 7.68MiB                                                  
  140          m4a        audio only DASH audio  128k , m4a_dash container, aac  @128k (44100Hz), 11.58MiB                              
  160          mp4        256x144    DASH video  112k , avc1.4d400c, 15fps, video only, 9.94MiB                                         
  278          webm       256x144    DASH video  136k , webm container, VP9, 15fps, video only, 9.10MiB                                 
  133          mp4        426x240    DASH video  248k , avc1.4d4015, 30fps, video only, 22.27MiB                                        
  242          webm       426x240    DASH video  316k , vp9, 30fps, video only, 22.20MiB                                                
  243          webm       640x360    DASH video  557k , vp9, 30fps, video only, 41.05MiB                                                
  134          mp4        640x360    DASH video  609k , avc1.4d401e, 30fps, video only, 52.94MiB                                        
  244          webm       854x480    DASH video 1021k , vp9, 30fps, video only, 74.05MiB                                                
  135          mp4        854x480    DASH video 1115k , avc1.4d401f, 30fps, video only, 97.02MiB                                        
  247          webm       1280x720   DASH video 2011k , vp9, 30fps, video only, 150.61MiB                                               
  136          mp4        1280x720   DASH video 2282k , avc1.4d401f, 30fps, video only, 189.40MiB                                       
  248          webm       1920x1080  DASH video 3838k , vp9, 30fps, video only, 286.61MiB                                               
  137          mp4        1920x1080  DASH video 4209k , avc1.640028, 30fps, video only, 354.19MiB                                       
  17           3gp        176x144                                                                                                       
  36           3gp        320x240                                                                                                       
  5            flv        400x240                                                                                                       
  43           webm       640x360                                                                                                       
  18           mp4        640x360                                                                                                       
  22           mp4        1280x720   (best)                                                                                             
  &gt; youtube-dl -f 137+140 'https://www.youtube.com/watch?v=VAdRBLyjLRQ&amp;feature=youtu.be&amp;t=8m14s'                      
  [youtube] Downloading login page                                                                                                      
  [youtube] Logging in                                                                                                                  
  [youtube] VAdRBLyjLRQ: Downloading webpage                                                                                            
  [youtube] VAdRBLyjLRQ: Downloading video info webpage                                                                                 
  [youtube] VAdRBLyjLRQ: Extracting video information                                                                                   
  (...)
  </code></pre>