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• how to automatically oversample and downsample when using filters ?

  4 juin 2021, par Yue Wang

  I am researching avfilters. Say I have an audio with sample rate s, and bit depth d,

  


  What I want to do is to write a graph that

  


  

  • upsample s by 4x, and set precision to 64bit float

  


  • apply some biquad filters with 64bit precision

  


  • downsample by 4x back to s, and set bit depth back to d.

  


  


  The reason to oversample is to get better filtering result by antialiasing, and the reason to downsample is to stream using the original source format.

  


  I don't know if there's way that I can do it automatically in the graph.

  


  ashowinfo could print out the sample rate, but seems there's no way to use the value later in the pipeline.

  


  asoftclip has a oversample factor. but it's not available in other filters.

  


• Can I stream 2 AVI or MP4 files to a user as if it were 1 file ?

  12 mars 2015, par Macmee

  I have several video files such as :

  bobs_video_part_1.mp4
  
  bobs_video_part_2.mp4
  
  bobs_video_part_3.mp4

  and instead of sending the user links to download each video separately :

  http://mynodejsserver.com/videos/bobs_video_part_1.mp4
  
  http://mynodejsserver.com/videos/bobs_video_part_2.mp4
  
  http://mynodejsserver.com/videos/bobs_video_part_3.mp4

  I want to be able to give the user just 1 link :

  http://mynodejsserver.com/videos/bobs_video.mp4

  I can combine the videos using something like ffmpeg but then I can’t give the user a link to the video in real time, I have to wait for ffmpeg to finish. I was thinking conceptually that this would work by doing something along the lines of :

  1. open file streams for each video and sum them to calculate total content-length
  
  2. open a stream/pipe back to the user and start sending data for bobs_video_part_1.mp4
  
  3. in that same stream start sending back bobs_video_part_2.mp4
  
  4. keep sending back the next video to the same stream/pipe to the user

  would something like this work ? Since I want to send each video in order anyway I don’t see why I can’t send each video as if it were part of the same video and the client doing the download request would never know.

• "Uncurve" Cinerama-like videos

  2 août 2021, par silent

  I'm pretty new to ffmpeg and I recently found interesting videos that are trying to simulate the Cinerama technology back from 1950x by curving the final video.

  


  Here is the screenshot how it looks like during the playback :

  


  I was wondering if it's possible to make this kind of picture back to "normal" rectangular shape ?
Here's a small (30 seconds, 48MB) example of how it looks like : https://ufile.io/8b0139j0

  


  Thanks !