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• How to change resolution without compromising video quality using ffmpeg ?

  20 mars 2024, par blake banker

  I'm trying to develop a simple video transcoding system.
When you upload a video,
After extracting the video and audio separately,
I want to encode them at 360, 720, and 1080p resolutions respectively and then merge them to create three final mp4 files.
At this time, I have two questions.

  


  


  1. Is there a big difference between encoding the video and audio separately in the original video file and encoding the original video file as is ? In a related book, it is said that a system is created by separating video and audio, and I am curious as to why.

     


  


  2. I want to change the resolution without compromising the original image quality. At this time, the resolution of the uploaded file can be known at the time of upload. As a test, I created files according to each resolution, and found that the image quality was damaged. If I want to change only the resolution while keeping the original image quality, I would like to know how to adjust each ffmpeg option. We plan to change it to 360, 720, and 1080p.

     


  


  


• How to clone last frame when using overlay in ffmpeg ? [closed]

  6 mai 2024, par mikezang

  I use this code to slide previous and next pages up, this is no problems, can I remove png file 1970～1979-last.png and use the last frame of video file 1970～1979.mp4 to instead it ?

  


  script-01.txt

  


  color=white:864x504[c];
[0:v]scale=864:504:force_original_aspect_ratio=decrease,pad=864:504:-1:-1,setsar=1[s0];
[1:v]scale=864:504:force_original_aspect_ratio=decrease,pad=864:504:-1:-1,setsar=1[s1];
[c][s0]overlay=y=0-h*t[c];
[c][s1]overlay=y='if(between(t,0,18),max(H-h*t,0),max(0-h*(t-18),0-H))'[v],
[v]tpad=stop_mode=clone:stop_duration=10[s2];
[s2]drawtext=fontfile='/WINDOWS/Fonts/Arial.ttf':text='%{eif\:18-t\:d}':
box=1:boxborderw=10:boxcolor=orange@0.4:
x=w-tw-10:y=10:fontsize=24:fontcolor=red:enable='between(t,8,18)';


  


  script-01.bat

  


  ffmpeg -hide_banner -loglevel fatal ^
    -loop 1 -i "C:\myimages\1970～1979-last.png" ^
    -i "C:\myvideos\years\1980～1989.mp4" ^
    -filter_complex_script script-01.txt ^
    -t 18 -y v01.mp4


  


  I got it what I only need video files and capture last frame by pipe line to next step, so that the last frame image never neede ! Though the first slide has little problem when countdown finished !

  


  script-01.bat

  


  ffmpeg -hide_banner -loglevel fatal ^
    -sseof -0.03 -i "C:\myvideos\years\1970～1979.mp4" ^
    -vframes 1 -c:v png -f image2pipe - | ffmpeg  ^
    -hide_banner -loglevel fatal -i - ^
    -i "C:\myvideos\years\1980～1989.mp4" ^
    -filter_complex_script script-01.txt ^
    -t 18 -y v01.mp4


  


• Output file not specified [closed]

  16 mai 2024, par Rich Madrid

  I have been messing around with ffmpeg working on basic mkv to mp4 conversions the last couple of days on my Mac and Windows computers. Mac was easier buy my windows desktop has a much faster OS so I wanted to do some conversions on it tonight. Got ffmpeg installed and working.

  


  After having some issues with the command prompt not finding the directory, I solved that with the following basic code to convert an mkv file to an mp4 for me :

  


  ffmpeg -i "C:\Users\Computer\videos\decade.mkv" "C:\Users\Computer\Videos\RJ videos\Complete\decade.mp4"


  


  I moved on to wanting to scale up an mkv to 1080p and use a yadif filter. I couldn’t find an adequate way to do this so I used a portion of the command that worked on my Mac last night, and stuffed it into the command for windows and I got an error code “at least one output file must be specified” after using the following command :

  


  ffmpeg -i "C:\Users\Computer\videos\decade.mkv" -vf "yadif=1,scale=1440x1080:flags=lanczos,setsar=1" -c:v libx264 -crf 21
-c:a aac -b:a 128k -ar 48k "C:\Users\Computer\Videos\RJ videos\Complete\decade.mp4"


  


  What am I doing wrong ?