<p>This can happen if the "streams do not have exactly the same length". You have to specify the range to include for the items in <code>concat.txt</code>. Try specifying the <code>duration</code> or <code>outpoint</code> or <code>in point</code>:</p>

<p><a href="https://ffmpeg.org/ffmpeg-formats.html#concat" rel="nofollow noreferrer">https://ffmpeg.org/ffmpeg-formats.html#concat</a></p>

<blockquote>
  <p>The duration of each file is used to adjust the timestamps of the next file: if the duration is incorrect (because it was computed using the bit-rate or because the file is truncated, for example), it can cause artifacts. The duration directive can be used to override the duration stored in each file.</p>
</blockquote>

CC BY-SA 3.0
2018-04-04T05:18:56.860Z
From the Q - *in between the concatenated files* - so not within the files.
Gyan
CC BY-SA 3.0
2018-04-04T11:22:03.607Z
Don't use `duration` - it is meant to override the value the concat demuxer uses for calculation, not for trimming -use. `outpoint` for that.
Gyan
CC BY-SA 3.0
2018-04-04T01:17:04.007Z
2018-04-04T06:01:56.800Z
2018-04-04T06:01:56.800Z
aleb
<p>I am using the concat demuxer in ffmpeg. I use the following command:</p>

<pre><code>ffmpeg -f concat -i concat.txt -c copy out.mkv
</code></pre>

<p>and it works, except that it adds short gaps of black frames in between the concatenated files (there are three of them). How do I make it stop? If it helps, the audio is cut at those points, too.</p>

<p>I know that a parameter for this exists, but I can't find the original question anywhere.</p>

<p>Thanks in advance.</p>

CC BY-SA 3.0
2018-04-04T05:19:46.877Z
Share the results of `ffprobe input` for all three files and also the content of concat.txt
Gyan
<ffmpeg><matroska>
How to disable putting black frames between concatenated media with ffmpeg?
Ginkgo
# How to disable putting black frames between concatenated media with ffmpeg?

(Asked by: username_0 on 2018-04-03)

I am using the concat demuxer in ffmpeg. I use the following command:
ffmpeg -f concat -i concat.txt -c copy out.mkv

and it works, except that it adds short gaps of black frames in between the concatenated files (there are three of them). How do I make it stop? If it helps, the audio is cut at those points, too.
I know that a parameter for this exists, but I can't find the original question anywhere.
Thanks in advance.

**Tags:** ffmpeg, matroska

> **Comments:**
> **username_1**: Share the results of `ffprobe input` for all three files and also the content of concat.txt  

---

## 1 answers

### Answer by username_2 on 2018-04-04. Score: 1

This can happen if the "streams do not have exactly the same length". You have to specify the range to include for the items in `concat.txt`. Try specifying the `duration` or `outpoint` or `in point`:

<https://ffmpeg.org/ffmpeg-formats.html#concat>

> The duration of each file is used to adjust the timestamps of the next file: if the duration is incorrect (because it was computed using the bit-rate or because the file is truncated, for example), it can cause artifacts. The duration directive can be used to override the duration stored in each file.

> **Comments:**
> **username_1**: From the Q - *in between the concatenated files* - so not within the files.  
> **username_1**: Don't use `duration` - it is meant to override the value the concat demuxer uses for calculation, not for trimming -use. `outpoint` for that.  

---

