Answers.Body: <p>Correction: instead of</p>
  
  <pre><code>ffmpeg -i output-audio.mp4 -i output-video.mp4 test-combine.mp4
  </code></pre>
  
  <p>it should be</p>
  
  <pre><code>ffmpeg -i output-audio.mp4 -i output-video.mp4 -shortest output-combine.mp4
  </code></pre>
  
  <p>Kind of answer:</p>
  
  <pre><code>ffmpeg -i output-video.mp4 -itsoffset 0.033333 -t 9.966666 -i output-audio.mp4  output-combine.mp4
  </code></pre>
  
  <p>seems to do the job, although the result differs in file-size slightly from an direct extraction (direct is bigger than combine) done with</p>
  
  <pre><code>ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 output-direct.mp4
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-05-13T13:51:01.007Z
Answers.LastActivityDate: 2018-05-13T13:51:01.007Z
Answers.UserDisplayName: Earl of Sandwich
Body: <p>When extracting audio and video separately from a mp4 and recombining again </p>
  
  <pre><code>ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 -vn output-audio.mp4
  ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 -an output-video.mp4
  ffmpeg -i output-audio.mp4 -i output-video.mp4 output-combine.mp4
  </code></pre>
  
  <p>the three mp4-s have different length according to ffprobe:</p>
  
  <pre><code>ffprobe output-video.mp4
  Duration: 00:00:10.00, start: 0.000000, ...
  ffprobe output-audio.mp4
  Duration: 00:00:10.03, start: 0.033333, ...
  ffprobe output-combine.mp4
  Duration: 00:00:10.08, start: 0.033333, ...
  </code></pre>
  
  <p>when combining audio and video with <code>-shortest</code></p>
  
  <pre><code>ffmpeg -i output-audio.mp4 -i output-video.mp4 test-combine.mp4
  </code></pre>
  
  <p>the length is</p>
  
  <pre><code>ffprobe output-combine.mp4
  Duration: 00:00:10.04, start: 0.033333, ...
  </code></pre>
  
  <p>How can the start-offset (0.033333) be avoided so that all parts have the same length and the original part can be restored by combining audio and video?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-05-13T13:25:53.537Z
Comments.Text: Share full log of `ffmpeg -i input.mp4`
Comments.UserDisplayName: Gyan
Tags: <video><ffmpeg><audio><mp4>
Title: ffmpeg: How to avoid "start: 0.033333" when extraction audio from mp4
UserDisplayName: Earl of Sandwich
ThreadText: # ffmpeg: How to avoid "start: 0.033333" when extraction audio from mp4
  
  (Asked by: username_0 on 2018-05-13)
  
  When extracting audio and video separately from a mp4 and recombining again
  
  ```
  ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 -vn output-audio.mp4
  ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 -an output-video.mp4
  ffmpeg -i output-audio.mp4 -i output-video.mp4 output-combine.mp4
  
  ```
  
  the three mp4-s have different length according to ffprobe:
  
  ```
  ffprobe output-video.mp4
  Duration: 00:00:10.00, start: 0.000000, ...
  ffprobe output-audio.mp4
  Duration: 00:00:10.03, start: 0.033333, ...
  ffprobe output-combine.mp4
  Duration: 00:00:10.08, start: 0.033333, ...
  
  ```
  
  when combining audio and video with `-shortest`
  
  ```
  ffmpeg -i output-audio.mp4 -i output-video.mp4 test-combine.mp4
  
  ```
  
  the length is
  
  ```
  ffprobe output-combine.mp4
  Duration: 00:00:10.04, start: 0.033333, ...
  
  ```
  
  How can the start-offset (0.033333) be avoided so that all parts have the same length and the original part can be restored by combining audio and video?
  
  **Tags:** video, ffmpeg, audio, mp4
  
  > **Comments:**
  > **username_1**: Share full log of `ffmpeg -i input.mp4`  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_0 on 2018-05-13. Score: 0
  
  Correction: instead of
  
  ```
  ffmpeg -i output-audio.mp4 -i output-video.mp4 test-combine.mp4
  
  ```
  
  it should be
  
  ```
  ffmpeg -i output-audio.mp4 -i output-video.mp4 -shortest output-combine.mp4
  
  ```
  
  Kind of answer:
  
  ```
  ffmpeg -i output-video.mp4 -itsoffset 0.033333 -t 9.966666 -i output-audio.mp4  output-combine.mp4
  
  ```
  
  seems to do the job, although the result differs in file-size slightly from an direct extraction (direct is bigger than combine) done with
  
  ```
  ffmpeg -accurate_seek -ss 30 -t 10 -i input.mp4 output-direct.mp4
  
  ```
  
  
  ---
  
  