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• Why do file length appears to be longer after using ffmpeg convert HEIC to PNG ?

  15 octobre 2024, par BrinyFish

  I have been moving all my photos from iphone to my windows PC. Because I don't like to keep all the files in HEIC format, so I used ffmpeg to try to batch convert all the photos from HEIC to PNG.

  


  Get-ChildItem *.heic | ForEach-Object {
    ffmpeg -i $_.FullName -map_metadata 0 -q:v 1 "$($_.BaseName).png"
}


  


  File size difference
After testing this chatGPT generated code on a small sample set of photos, I realize that the length of the PNG photos are smaller than the length of the HEIC photos. I have always believed that HEIC is the compressed format, which should be smaller. However, this size difference really makes me wonder if I am losing resultion or meta data. Do anyone know why would this be the case ?

  


  I have googled and most articles are saying that HEIC should be smaller than PNG, which don't help me in this case.

  


• ffmpeg modify audio length/size ( stretch or shrink)

  14 juin 2016, par mido

  I am developing a web app, where people can record videos. I have been able to send chunks of audio n video to server successfully, where I am trying to combine them and return as single proper file.

  my problem is if the recording is for one hour, after merging the chunks

  video length : 1:00:00 , audio length : 00:59:30,

  now, this is not a issue of audio not getting recorded( I have checked that), the problem is, somehow, when i merge the chunks of audio, it shrinks,

  I find that it is progressive sync issue where it gets worse and worse as time increases.

  I have searched the net for the solution, most places say async, I have tried using it, but to no avail, is the below usage correct ?

  ffmpeg  -i audio.wav -async 1 -i video.webm -y -strict -2 v.mp4

  (v.mp4 is the final file that I provide to the users.)

• ffmpeg modify audio length/size ( stretch or shrink)

  24 janvier 2024, par mido

  I am developing a web app, where people can record videos. I have been able to send chunks of audio n video to server successfully, where I am trying to combine them and return as single proper file.

  



  my problem is if the recording is for one hour, after merging the chunks

  



  video length : 1:00:00 , audio length : 00:59:30,

  



  now, this is not a issue of audio not getting recorded( I have checked that), the problem is, somehow, when i merge the chunks of audio, it shrinks,

  



  


  I find that it is progressive sync issue where it gets worse and worse as time increases.

  


  



  I have searched the net for the solution, most places say async, I have tried using it, but to no avail, is the below usage correct ?

  



  ffmpeg  -i audio.wav -async 1 -i video.webm -y -strict -2 v.mp4

  



  (v.mp4 is the final file that I provide to the users.)