Answers.Body: <p>Inside a filtergraph, each pad is associated with a single stream. And a specifier such as <code>0:a</code> will match the first stream that qualifies. You need to specify two pads and fully specify the input streams.</p>
  <pre><code>[0:a:0][0:a:1]amerge=inputs=2[a]
  </code></pre>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-21T06:34:51.737Z
Answers.Text: Will this throw an error if only one input audio stream is inputted? I'm using it in a kind of automated program, and some videos may only have one audio stream, while others may have 2.
Answers.UserDisplayName: pigeonburger
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-21T08:01:17.530Z
Answers.Text: No. of inputs should be equal to the inputs value of amerge.
Answers.UserDisplayName: Gyan
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-11-21T04:48:53.333Z
Answers.LastActivityDate: 2020-11-21T04:48:53.333Z
Answers.UserDisplayName: Gyan
Body: <p>The error I'm getting is in the title.</p>
  <p>I want to merge the two audio streams from a video into one (yes, I've checked if there is two and there is). This is the command I'm using:</p>
  <pre><code>ffmpeg -i input.mp4 -filter_complex &quot;[0:v]scale=-2:720,format=yuv420p[v];[0:a]amerge=inputs=2[a]&quot; -map &quot;[v]&quot; -map &quot;[a]&quot; -c:v libx264 -crf 23 -preset medium -c:a aac -ar 44100 -ac 2 output.mp4
  </code></pre>
  <p>Any ideas why I could be getting the error?</p>
  
Tags: <video><ffmpeg><audio>
Title: "Cannot find a matching stream for unlabeled input pad 2 on filter Parsed_amerge_2" ffmpeg
UserDisplayName: pigeonburger
ThreadText: # "Cannot find a matching stream for unlabeled input pad 2 on filter Parsed_amerge_2" ffmpeg
  
  (Asked by: username_0 on 2020-11-20)
  
  The error I'm getting is in the title.
  
  I want to merge the two audio streams from a video into one (yes, I've checked if there is two and there is). This is the command I'm using:
  
  ```
  ffmpeg -i input.mp4 -filter_complex "[0:v]scale=-2:720,format=yuv420p[v];[0:a]amerge=inputs=2[a]" -map "[v]" -map "[a]" -c:v libx264 -crf 23 -preset medium -c:a aac -ar 44100 -ac 2 output.mp4
  
  ```
  
  Any ideas why I could be getting the error?
  
  **Tags:** video, ffmpeg, audio
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2020-11-21. Score: 0 | Accepted answer
  
  Inside a filtergraph, each pad is associated with a single stream. And a specifier such as `0:a` will match the first stream that qualifies. You need to specify two pads and fully specify the input streams.
  
  ```
  [0:a:0][0:a:1]amerge=inputs=2[a]
  
  ```
  
  > **Comments:**
  > **username_0**: Will this throw an error if only one input audio stream is inputted? I'm using it in a kind of automated program, and some videos may only have one audio stream, while others may have 2.  
  > **username_1**: No. of inputs should be equal to the inputs value of amerge.  
  
  ---
  
  