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• How to add multiple audio to video file at a specific time using ffmpeg

  13 mai 2018, par 呂裕翔

  I can add one audio to video by using

  ffmpeg -i input_video -i input_audio -filter_complex "
  
  aevalsrc=0:d=30[s1];
  
  [s1][1:a]concat=n=2:v=0:a=1[aout]" -c:v copy -map 0:v -map [aout] output_video

  I have no idea how I can add two, three,... audio to video.
  I have searched a lot of post, but I can not find the correct answer.
  Thank for your help.

• Remove frames based off an image with FFmpeg

  15 novembre 2020, par VEXED

  The Goal : Take a frame or a reference image and use that to decide what frames to keep/remove from an old screen recording (no audio).

  


  To be slightly more specific, I want to match a specific program that is being used in the screen recording. The program is always full screen and could potentially be identified just by a crop of the top left corner.

  


  The Question : What would be the best way to take an image, in particular a cropped corner of say 100px width and height, and look for the same matching corner in a video ? I would want to output those matches to a new file, that or remove the non-matching frames and create a new file with all the frames that match.

  


  What I Know : I know that duplicate frame removal is very possible, and I already use that for screen recordings.

  


  -filter:v mpdecimate, setpts=N/FRAME_RATE/TB \


  


  The above is being used in my screen recording script to remove duplicate frames.

  


  I'm also aware that you can crop using FFmpeg, but I'm not looking to have actual cropped output. I'm only looking to use a crop to find the portion that matches my reference image or reference frame.

  


  ffmpeg -i in.mp4 -filter:v "crop=out_w:out_h:x:y" out.mp4


  


  The above is a basic crop.

  


  The only reference to finding frames by images is this one. It didn't do what I wanted and just produced dark and distorted output. Though I might be understanding what the aim of that post was incorrectly.

  


  Notes : Thanks in advance for any help, this frame/image matching doesn't have to be done while recording, but can be done in post.

  


• ffmpeg-python video conversion error : malloc of size 36254012 failed on Raspberry Pi

  23 novembre 2021, par Bob Smith

  I am trying to convert a .mkv file into .mp4 format using the ffmpeg-python python library. I have been able to run my script on a Windows machine repeatedly without any issues, however when I run the same script on a Raspberry Pi 4 B I am faced with the same error again and again. Similar to this post, I am faced with the following message :

  


  x264 [error]: malloc of size 36254012 failed
Video encoding failed


  


  I have tried setting max_muxing_queue_size to 9999 as heard this might fix the issue, it had no effect. I tried increasing the gpu RAM from the default 128 MB to as much as 512 MB (I have the 8 GB RAM model so I was not concerned about overall system memory), needless to say this had no effect either.

  


  Finally, I read on a forumn post from someone else with the same error that decresing the number of threads ffmpeg uses to 1 might also solve this issue. This did in fact solve my problem, unfortunately it decreases the speed of the process to a crawl of what it would otherwise be. I was hoping someone might have another idea of how to fix this that would still allow for multiple threads to be used by ffmpeg, or at least have some idea as to what might be causing this issue.

  


  Also it's not particularly useful, but for reference the line that is causing the exception in the code is the following :

  


  ffmpeg.input(video_file).output(out_name, **{'max_muxing_queue_size': '9999'}).run()