Body: <p>I saw this answer <a href="https://video.stackexchange.com/questions/29904/ffmpeg-batch-overlay-error-cannot-find-a-matching-stream-for-unlabeled-input-p">ffmpeg batch overlay Error: &quot;Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_overlay_0&quot;</a> for same error message but doesn't seem to be same case :</p>
  <p>I first converted 2 gifs of same width and height to mp4 using ffmpeg options</p>
  <pre><code>ffmpeg -i video1.gif -movflags faststart -pix_fmt yuv420p -vf &quot;scale=trunc(iw/2)*2:trunc(ih/2)*2&quot; video1.mp4
  ffmpeg -i video2.gif -movflags faststart -pix_fmt yuv420p -vf &quot;scale=trunc(iw/2)*2:trunc(ih/2)*2&quot; video2.mp4
  </code></pre>
  <p>afterwards I joined with</p>
  <pre><code>ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex &quot;concat=n=2:v=1:a=1&quot; -f MP4 -y video.mp4
  </code></pre>
  <p>But I got error</p>
  <pre><code>Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_concat_0
  </code></pre>
  <p>with other mp4 in the past joining works so I don't understand why.</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-11-20T15:08:14.353Z
Comments.Text: Share full command that you tried.
Comments.UserDisplayName: Gyan
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-11-20T17:23:04.047Z
Comments.Text: @Gyan updated my question
Comments.UserDisplayName: user310291
Tags: <ffmpeg>
Title: Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_concat_0 (a different case)
UserDisplayName: user310291
ThreadText: # Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_concat_0 (a different case)
  
  (Asked by: username_0 on 2020-11-20)
  
  I saw this answer [ffmpeg batch overlay Error: "Cannot find a matching stream for unlabeled input pad 1 on filter Parsed\_overlay\_0"](https://video.stackexchange.com/questions/29904/ffmpeg-batch-overlay-error-cannot-find-a-matching-stream-for-unlabeled-input-p) for same error message but doesn't seem to be same case :
  
  I first converted 2 gifs of same width and height to mp4 using ffmpeg options
  
  ```
  ffmpeg -i video1.gif -movflags faststart -pix_fmt yuv420p -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" video1.mp4
  ffmpeg -i video2.gif -movflags faststart -pix_fmt yuv420p -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" video2.mp4
  
  ```
  
  afterwards I joined with
  
  ```
  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex "concat=n=2:v=1:a=1" -f MP4 -y video.mp4
  
  ```
  
  But I got error
  
  ```
  Cannot find a matching stream for unlabeled input pad 1 on filter Parsed_concat_0
  
  ```
  
  with other mp4 in the past joining works so I don't understand why.
  
  **Tags:** ffmpeg
  
  > **Comments:**
  > **username_1**: Share full command that you tried.  
  > **username_0**: @username_1 updated my question  
  
  ---
  
  ## 0 answers
  
  