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• ffmpeg 4 channel assignment with amerge

  29 mai 2014, par kava

  I combine two stereo files to one 4 channel file with :

  ffmpeg -i 1.wav -i 2.wav -filter_complex "amerge=inputs=2" -c:a pcm_s24le out.wav

  This works fine, but when I open the file in Quicktime or want to edit it in other applications the quicktime channel assignment is L/C/R/SURR. But I want it to be QUAD - L/R/LS/RS. How can I tell ffmpeg to set these assignments ?

• How can I convert a regular WAV file to a 4bit WAV file using ffmpeg ?

  17 février 2020, par Florin Mircea

  I have tried something along the lines of

  C :\ffmpeg\ffmpeg -i "Blip_Select2.wav" -c:a wav -sample_fmt u8 "Blip_Select2_8bit.wav"

  but I cannot figure out how to access a 4bit conversion.

  I am using the audio for a c# project, 4 bit is sufficient and I prefer wav so I won’t have to distribute a possibly restricted usage decoder with my files.

  Edit. I have found a solution using a different software (see my answer below), but I am accepting Mattias’s answer as he provided the solution as asked, with ffmpeg.

• How to create a fixed image video with ffmpeg that avoids pixelization when it's not maximized ?

  11 août 2022, par Nelson Teixeira

  I have a waiting video in the project I develop. This video is a fixed waiting image with music. I was asked to change the image in the video due to deprecated logo.

  


  So initially I tried just to replace the image in the video using this command :

  


  ffmpeg -i old_waiting_video.mp4 -i new_image.png -filter_complex "[1][0]scale2ref[i][v];[v][i]overlay" -c:a copy new_waiting_video.mp4


  


  This lead to the image became pixelated when the video isn't maximized. When maximized the image is OK. But it looks terrible in the small player.

  


  Here is an image of the problem :

  


  

  


  The above image is the image without zoom out. The left bottom image is a screen capture when I resize it in an image tool and the right bottom is a screen capture of how it looks like in the player.
The image has more than this text, but I thought that wouldn't be appropriate to display my company's logo here. The logo itself is even more pixelized and looks terrible.

  


  So to try to solve this problem I extracted the audio from the file and try to add the image and the audio together to see if it removed the pixelization. So I used this command :

  


  ffmpeg -i audio.m4a -i new_image.png new_waiting_video.mp4


  


  When it failed, searching a bit I came across this other command :

  


  ffmpeg -loop 1 -i new_image.png -i audio.m4a -c:v libx264 -tune stillimage -c:a copy -pix_fmt yuv420p -shortest new_waiting_video.mp4


  


  Again the pixelization ocurred. I know it's possible because this problem doesn't occur in the old logo.

  


  What would be the correct command that allowed that the zoomed out image in the player doesn't pixelate ?

  


  Edit 1

  


  I would also be interested in a command that substitutes the image on the old video as long it doesn't pixelate in the non-maximized player.

  


  Edit 2

  


  

  • Video resolution : 1920x1080

  


  • New image resolution : 1920x1080

  


  • Non-maximized video player size : 640x360

  


  • Video tag : <video src="my-video-url.mp4" style="width: 640px;"></video>