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• ffmpeg clip audio interval with starting and end time

  31 mars 2017, par Raymond Huang

  I am trying to clip an MP3 between two starting points, like starting at 10 seconds and ending at 16 seconds (time interval of 6 seconds).

  I am using this command :

  ffmpeg -ss 10 -i input.mp3 -t 6 output.mp3

  The resulting output.mp3 contains the 6 seconds that I specified followed by 8 or 9 seconds of empty audio. Is there something wrong with my command ?

  Edit :

  ffmpeg -ss 10 -t 6 -i input.mp3 output.mp3 says -t is not an input option, keeping it for the next output; consider fixing your command line. and gives me a file that’s got 8 seconds of audio starting from 10s and then some 9 or 10 seconds of silence.

  ffmpeg -ss 10 -to 16 -i input.mp3 output.mp3 produces a file that is twice the length of the original - basically the same audio file repeated again.

  Testing the output :

  I used Quicktime and it has silent audio at the end. The description of the output file in finder says like 14 seconds. When I use VLC, it plays for the correct 6 seconds and stops, even though its duration in the file browser in VLC says 14. My MPlayer doesn’t work properly. I also did the preview audio in Finder, and it plays the 6 seconds properly and then stops. But the round seeker bar of the MP3 didn’t reach the end. And it also says 14 seconds instead of 6.

  My goal is to stream this 6 second file through a REST API to the front end. I want the user to be able to download this file properly. Ideally it won’t have inconsistent metadata (14 seconds instead of 6).

• Node.js Webm live stream server : issues with tag

  10 décembre 2013, par breathe0

  I'm using Node.js as stream server to stream realtime Webm videos that is sent by FFMPEG (executed from another application, the stream is done via HTTP) and received by a webapp that uses the tag.

  This is what I'm doing : FFMPEG streams the received frames using the following command :

  ffmpeg -r 30 -f rawvideo  -pix_fmt bgra -s 640x480 
  
  -i \\.\pipe\STREAM_PIPE -r 60 
  
  -f segment  -s 240x160 -codec:v libvpx  -f webm 
  
  http://my.domain.com/video_stream.webm

  (the stream comes from an application that uses the Kinect as source and communicates with FFMPEG through a pipe, sending one frame after another)

  When the webapp connects, it receives immediately this response from the server :

  HTTP/1.1 200 OK
  
  X-Powered-By: Express
  
  content-type: video/webm
  
  cache-control: private
  
  connection: close
  
  Date: Fri, 06 Dec 2013 14:36:31 GMT

  and a Webm header (previously stored on the server, with the same resolution and frame rate of the source stream and tested as working on VLC) is immediately appended. Then the webapp starts to receive the data streamed by FFMPEG. Here is a screenshot of Mkvinfo GUI showing the fields of the header :

  

  However, even if the Network tab of the Chrome console shows that there is an actual stream of data (meaning that what is streamed is not completely garbage, otherwise the connection would be dropped), the player doesn't display anything. We tried to manually prepend our header to the dumped video received by the webapp and VLC plays it just fine, but this is not happening with the tag.

  What can cause this problem ? Are we missing something about the encoding on the FFMPEG side or we stored wrong values on the header (or they're not enough) ?

  PS : I cannot rely on an extern stream server.

  PPS : We tried the following experiments :

  • substituting the video header with the one stored in the server makes the video playable on both vlc and video tag
  • if we dump the video that is already started (without an header) and we prepend the video header stored in the server or even its original header, the video is playable in VLC but not on the tag (we're carefully prepending the header just before the beggining of the cluster).

• FFMPEG MP4s are corrupt in Firefox after rotation ? [migrated]

  13 décembre 2013, par Paul

  I'm working on a website that allows uploading of generic video types, converts them to MP4s (H.264), then plays them using the HTML 5 <video></video> tag.

  I would really like to give the option to rotate videos, but when I run the rotation, the output files will not play in Firefox ("Video cannot be played because the file is corrupt"). Windows also does not automatically generate a thumbnail based on its content, like for other MP4s. The files do play fine in VLC and in Chrome, but I will need them to work in Firefox as well.

  I've tried joining the conversion and rotation into a single FFMPEG call, and I've also tried rotating before converting and vice-versa, but I still have the same problem.

  Here are what my calls look like :

  Rotation :

   ffmpeg -i <input /> -vf "transpose=1" -qscale 0 -y -acodec copy <output>
  
  </output>

  Conversion :

   ffmpeg -i <input /> -vcodec libx264 -vsync 1 -bt 50k -acodec libvo_aacenc -crf <quality> -s <width>x<height> -ar 44100 -ab 160 -ac 2 -y <output>
  
  </output></height></width></quality>