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• HLS from node to iOS app

  16 novembre 2016, par Carol

  I created a API in node that you can upload a video (.mp4, .avi, etc). Then, the video is request by a iOS app in swift.

  I would like to use HTTP Live streaming from the app. Can you help me how can I transform the video file to chunks .ts and generate the playlist file (m3u8) to be consumed by the app ?

  This is the correct flow ?
  What it’s the best solution ?

  Thanks !

• Can FFMPEG be used to change the transparency of a single PNG ?

  19 juillet 2020, par Chameleon

  I know that FFMPEG can manipulate transparency using fade in/fade out over a series of frames. I just haven't found a way to generate a png with a specified transparency setting.

  


  I am in the process of creating a lot (20 in first set) of procedurally-generated videos. Each video requires several starts and stops, where with each stop, a png overlay describing what is seen will be displayed for several (actual number TBD, and may vary) frames. I'd like each overlay to fade in over x frames, display for y frames at full opacity and then fade out over y frames. The documentation on FFMPEG really sucks at explaining fade effects, and no one I've found showing usage actually explains what all of the parameters do.

  


  The original sources for the videos are CGI png frames with a transparent background. I will be making the descriptive overlays with transparent backgrounds (same resolution as the CGI frames) - I'm really hoping to not have to manually save each overlay (8 overlays per video at a minimum) with 4 to 6 (or more) transparency settings - The company is being real indecisive as to the length of the fade in/out or the "hang time" of the descriptive overlays.

  


  I have already created a Python script that uses FFMPEG to place overlays on specific frames, then uses FFMPEG to stitch all frames into a single video, adds a background to the video and then places the company's watermark on the video. It already manages the key frames and what images should be overlaid (and for how many frames). It is working well, but the company doesn't like the lack of fade. I already have the framework in place to manage the fade in/out duration (I'm just missing the answer to this question). I created the script because I have no doubt that I'll have to generate the final output on the first couple of videos a number of times to appease the stakeholders.

  


  I'm really hoping to find a fairly easy way to hand FFMPEG a png with a transparent background and have FFMPEG hand me a copy of the image whose non-transparent part is now "x percent" transparent (or "y percent" opaque). I know from failed attempts that FFMPEG doesn't choke trying to make a region more than 100% transparent.

  


  It's a real pain to get approval to install new software on the workstation, so I'm not actually interested in any suggestion that doesn't use FFMPEG or a pretty vanilla Python installation. - It's not that the other software might not be useful, it just means that if other software is needed, I'll have to manually create the frames.

  


• ffmpeg works fine most of the time in java except for this command (merging), and this command works fine directly in terminal

  14 mai 2014, par Ron I

  When I run this from the command line it works (merges two videos side by side) :

  /usr/local/bin/ffmpeg -i /Users/ron/Dropbox/JAMR/Technology/workspace/JAMR/sandbox/test.mov -i /Users/ron/Dropbox/JAMR/Technology/workspace/JAMR/sandbox/test1.mov -filter_complex "[0:v:0]pad=iw*2:ih[bg]; [bg][1:v:0]overlay=w" /Users/ron/Dropbox/JAMR/Technology/workspace/JAMR/sandbox/merged.mov

  However, when I run it in java, I get this from the console :

  [AVFilterGraph @ 0x7fd44ad00440] No such filter: '"'
  
  Error configuring filters.

  here is the text I am returning (copied directly) which is what I am sending to be executed. It is exactly the same, except I use the escape character before the quote symbol, so a " becomes \" :

  "/usr/local/bin/ffmpeg -i /Users/ron/Dropbox/JAMR/Technology/workspace/JAMR/sandbox/test.mov -i /Users/ron/Dropbox/JAMR/Technology/workspace/JAMR/sandbox/test1.mov -filter_complex \"[0:v:0]pad=iw*2:ih[bg]; [bg][1:v:0]overlay=w\" /Users/ron/Dropbox/JAMR/Technology/workspace/JAMR/sandbox/merged.mov";

  All other ffmpeg tests have worked except this.... (the only one where I use a " character)

  Can anyone figure it out ?