Body: <p>I use ffmpeg to:</p>
  
  <ol>
  <li>add multiple audio into a video file and offset them </li>
  <li>discard original audio in the video </li>
  </ol>
  
  <p>Everything is OK <strong>except</strong> that 
  1. the audio volume in the <code>result.mp4</code> is remarkably lower than the volumes in each individual input audio
  2. sound quality in <code>mp3</code>(which is a background music) also drops</p>
  
  <p>I listened to each <code>3gp</code> and the <code>mp3</code> files, can confirm that the two issues above.</p>
  
  <p>Why is this happening?</p>
  
  <pre><code>ffmpeg -i 1.mp4 -i 1.3gp -i 2.3gp -i 1.mp3
    -filter_complex "[2]adelay=10000|10000[s2];[3:a][1:a][s2]amix=3[a]"
    -map 0:v -map "[a]" -c:v copy result.mp4
  </code></pre>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-07-24T13:09:57.773Z
Comments.Text: See https://stackoverflow.com/a/38714779/5726027
Comments.UserDisplayName: Gyan
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-07-24T15:27:59.740Z
Comments.Text: Thanks, I was also checking that thread. The command there works better, but still it does generate an optimal result. For example, at the begin of 5 secs, there is only one mp3 file as audio input, but the volume is still very low. From a noob point of view, why can't ffmpeg just stack these audios up then generate result?
Comments.UserDisplayName: Xi Xiao
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-07-24T15:46:20.570Z
Comments.Text: I checked your explanation @Mulvya in that thread. In my case, there is always two active audio inputs at any given time, one is the mp3, the other one is a 3gp, i.e. none 3gp files overlaps.
Comments.UserDisplayName: Xi Xiao
Tags: <ffmpeg>
Title: Audio volume lower, quality drops after ffmpeg amix multiple audio inputs
UserDisplayName: Xi Xiao
ThreadText: # Audio volume lower, quality drops after ffmpeg amix multiple audio inputs
  
  (Asked by: username_0 on 2017-07-24)
  
  I use ffmpeg to:
  
  1. add multiple audio into a video file and offset them
  2. discard original audio in the video
  
  Everything is OK **except** that
  1. the audio volume in the `result.mp4` is remarkably lower than the volumes in each individual input audio
  2. sound quality in `mp3`(which is a background music) also drops
  
  I listened to each `3gp` and the `mp3` files, can confirm that the two issues above.
  
  Why is this happening?
  
  ```
  ffmpeg -i 1.mp4 -i 1.3gp -i 2.3gp -i 1.mp3
    -filter_complex "[2]adelay=10000|10000[s2];[3:a][1:a][s2]amix=3[a]"
    -map 0:v -map "[a]" -c:v copy result.mp4
  
  ```
  
  **Tags:** ffmpeg
  
  > **Comments:**
  > **username_1**: See https://stackoverflow.com/a/38714779/5726027  
  > **username_0**: Thanks, I was also checking that thread. The command there works better, but still it does generate an optimal result. For example, at the begin of 5 secs, there is only one mp3 file as audio input, but the volume is still very low. From a noob point of view, why can't ffmpeg just stack these audios up then generate result?  
  > **username_0**: I checked your explanation @Mulvya in that thread. In my case, there is always two active audio inputs at any given time, one is the mp3, the other one is a 3gp, i.e. none 3gp files overlaps.  
  
  ---
  
  ## 0 answers
  
  