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• FFMPEG no audio / broken audio after concat

  18 octobre 2018, par Noniq

  First, I’m converting from mp3 to mp4, using a jpg file as background :

  ffmpeg -loop 1 -i bg.jpg -i song.mp3 -c:a copy -c:v libx264 -shortest output.mp4

  Then, I’m trying to concatenate multiple mp4 files to a video :

  ffmpeg -f concat -safe 0 -i list.txt -c copy mix.mp4

  list.txt contains a list of video files :

  file 'output1.mp4'
  
  file 'output2.mp4'

  Problem : After concat, the audio stream isn’t working properly. The audio of the first video is correct, but for the second video it’s either silent (Groove Music player, Chrome) or when uploaded to YouTube, it skips like every third of a second.
  Only in VLC media player it’s working properly.

  Every file used to be an mp3 file and is converted to mp4 using the same encoding options - thus I expected it to work with demuxing - but apparently, something went wrong.

• Creating video from audio and resized image using FFMPEG

  20 décembre 2016, par nemeskeriors

  Im trying to create an mp4 video from an mp3 and an image with ffmpeg. The video should be the size of 640x360 with black background and the image should be resized to fit in this dimensions and centered in the middle. The video’s lenght must match the mp3’s length.

  Its basically a video creation for youtube from a song and an artwork.

  For now i was able to achive this with 3 steps :

  1. resize image :

  -i %image% -vf scale='if(gt(a,4/3),640,-1)':'if(gt(a,4/3),-1,360)' %resized_image%

  2. create a music video with black background :

  -f lavfi -i color=s=640x360 -i %audio_file% -c:v libx264 -s:v 640x360 -c:a aac -strict experimental -b:a 320k -shortest -pix_fmt yuv420p %video%

  3. put the resized image cenetered in the video :

  -i %video% -i %resized_image% -filter_complex "overlay=(W-w)/2:(H-h)/2" -codec:a copy %final_video%

  Is it possible to achive all this with one ffmpeg command ?

• FFMpeg : audio resampling changes slightly the speed of the music [on hold]

  24 octobre 2018, par thenaoh

  In my Android app, I use the FFMpeg library to extract audio samples from an audio file on the fly, and also resample them (since my file is encoded in 44100 Hz, and my device expects 48000 Hz sound).

  The problem is : even if the sound quality is perfect, the speed is a little bit higher than the regular speed of the music.

  The difference is very small (small enough so you won’t hear it), but you can hear it when you play the same song at the same time on a regular player (like VLC for example).

  I think it comes from the resampling, but I don’t know how to fix it.

  Here is my code (I get my samples thanks to the getPcmFloat() function) : https://gist.github.com/mregnauld/2538d98308ad57eb75cfcd36aab5099a

  How can I correct the speed of the music ?

  Thanks for your help.