<p>From time to time i'm converting mkv to mp4 using ffmpeg in order to save disk space. 
Currently i noticed that in some files multiple mjpeg streams where also included. Some of them were named <code>cover.jpg</code>.  </p>

<p>From the name <code>cover.jpg</code> i assume that it is supposed to be displayed in some cases?!? But i never heard or saw that any program, eg. vlc, used an image to display anything from the video. So what is the use case of including pictures in a video file? </p>

<p>The files have one <code>normal</code> video stream, maybe multiple audio streams, and about 4 mjpeg streams.</p>

CC BY-SA 4.0
2019-06-27T01:14:16.267Z
Post the command you used.
stib
CC BY-SA 4.0
2019-06-28T19:59:04.447Z
It is in the video file, I didn't add it there. I don't understand the use case of it
Ronon
CC BY-SA 4.0
2019-06-29T10:51:23.100Z
mkv, like mp4 is a container format that is able to contain many different streams, including video, audio, subtitles, metadata and images. I'd guess that cover.jpg contains a poster image for displaying on a media playback system. BTW it's not the container format that dictates the size of the file. Mp4 isn't any more space efficient than mkv.
stib
CC BY-SA 4.0
2019-07-01T22:59:28.770Z
Never saw the cover.jpg in action on any kind of player. MP4 ist web playable, thats why I use this format instead of keeping it as mkv
Ronon
CC BY-SA 4.0
2019-07-02T01:31:43.923Z
Kodi and other media centres use cover.jpg to show the poster image in their menus. Where did the videos come from? https://www.matroska.org/technical/cover_art/index.html
stib
<video><mkv>
Mjpeg in video containers use case
Ronon
# Mjpeg in video containers use case

(Asked by: username_0 on 2019-06-24)

From time to time i'm converting mkv to mp4 using ffmpeg in order to save disk space.
Currently i noticed that in some files multiple mjpeg streams where also included. Some of them were named `cover.jpg`.

From the name `cover.jpg` i assume that it is supposed to be displayed in some cases?!? But i never heard or saw that any program, eg. vlc, used an image to display anything from the video. So what is the use case of including pictures in a video file?

The files have one `normal` video stream, maybe multiple audio streams, and about 4 mjpeg streams.

**Tags:** video, mkv

> **Comments:**
> **username_1**: Post the command you used.  
> **username_0**: It is in the video file, I didn't add it there. I don't understand the use case of it  
> **username_1**: mkv, like mp4 is a container format that is able to contain many different streams, including video, audio, subtitles, metadata and images. I'd guess that cover.jpg contains a poster image for displaying on a media playback system. BTW it's not the container format that dictates the size of the file. Mp4 isn't any more space efficient than mkv.  
> **username_0**: Never saw the cover.jpg in action on any kind of player. MP4 ist web playable, thats why I use this format instead of keeping it as mkv  
> **username_1**: Kodi and other media centres use cover.jpg to show the poster image in their menus. Where did the videos come from? https://www.matroska.org/technical/cover_art/index.html  

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## 0 answers

