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MKV thumbnail not correctly embedded #8476

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opened 2026-02-21 04:23:29 -05:00 by deekerman · 8 comments

deekerman commented

2026-02-21 04:23:29 -05:00

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Originally created by @ghost on GitHub (Aug 16, 2016).

I've verified and I assure that I'm running youtube-dl 2016.08.13
At least skimmed through README and most notably FAQ and BUGS sections
Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

Bug report (encountered problems with youtube-dl)
Site support request (request for adding support for a new site)
Feature request (request for a new functionality)
Question
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When using --embed-thumbnail, it seems that the thumbnail isn't added as an image resource (cover.jpg) to the mkv video file but instead added as a second video stream. Seemingly using the same code as is used for embedding cover art for a mp3. This results in the embedded thumbnail not being displayed and instead no thumbnail or a automatically generated one being shown.

Tested with this video:
https://www.youtube.com/watch?v=k_okcNVZqqI
youtube-dl https://www.youtube.com/watch?v=k_okcNVZqqI --embed-thumbnail
Using youtube-dl 2016.08.13 and ffmpeg-20160815-3282e31-win64-static

MediaInfo, thumbnail embedded with --embed-thumbnail:
INK DROPS 4K (ULTRA HD)-k_okcNVZqqI.mkv.MediaInfo.txt

MediaInfo, thumbnail embedded with mkvpropedit:
INK DROPS 4K (ULTRA HD)-k_okcNVZqqI-proper.mkv.MediaInfo.txt

Related to this the request for thumbnail embedding support for webm files when this is fixed. (#10360)

Originally created by @ghost on GitHub (Aug 16, 2016). - [x] I've **verified** and **I assure** that I'm running youtube-dl **2016.08.13** - [x] At least skimmed through [README](https://github.com/rg3/youtube-dl/blob/master/README.md) and **most notably** [FAQ](https://github.com/rg3/youtube-dl#faq) and [BUGS](https://github.com/rg3/youtube-dl#bugs) sections - [x] [Searched](https://github.com/rg3/youtube-dl/search?type=Issues) the bugtracker for similar issues including closed ones ### What is the purpose of your _issue_? - [x] Bug report (encountered problems with youtube-dl) - [ ] Site support request (request for adding support for a new site) - [ ] Feature request (request for a new functionality) - [ ] Question - [ ] Other --- When using --embed-thumbnail, it seems that the thumbnail isn't added as an image resource (cover.jpg) to the mkv video file but instead added as a second video stream. Seemingly using the same code as is used for embedding cover art for a mp3. This results in the embedded thumbnail not being displayed and instead no thumbnail or a automatically generated one being shown. Tested with this video: https://www.youtube.com/watch?v=k_okcNVZqqI youtube-dl https://www.youtube.com/watch?v=k_okcNVZqqI --embed-thumbnail Using youtube-dl 2016.08.13 and ffmpeg-20160815-3282e31-win64-static MediaInfo, thumbnail embedded with --embed-thumbnail: [INK DROPS 4K (ULTRA HD)-k_okcNVZqqI.mkv.MediaInfo.txt](https://github.com/rg3/youtube-dl/files/420888/INK.DROPS.4K.ULTRA.HD.-k_okcNVZqqI.mkv.MediaInfo.txt) MediaInfo, thumbnail embedded with mkvpropedit: [INK DROPS 4K (ULTRA HD)-k_okcNVZqqI-proper.mkv.MediaInfo.txt](https://github.com/rg3/youtube-dl/files/420889/INK.DROPS.4K.ULTRA.HD.-k_okcNVZqqI-proper.mkv.MediaInfo.txt) Related to this the request for thumbnail embedding support for webm files when this is fixed. (#10360)

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2026-02-21 04:23:29 -05:00

deekerman commented

2026-02-21 04:23:31 -05:00

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@yan12125 commented on GitHub (Aug 23, 2016):

This results in the embedded thumbnail not being displayed

Sorry for being late. Which player are you using?

@yan12125 commented on GitHub (Aug 23, 2016): > This results in the embedded thumbnail not being displayed Sorry for being late. Which player are you using?

deekerman commented

2026-02-21 04:23:32 -05:00

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@ghost commented on GitHub (Aug 25, 2016):

I mainly use a software called Icaros which enables MKV files showing thumbnails in windows explorer using the thumbnail inside the file or, if there is no thumbnail inside it, using a generated one.

But I see the same thing with Windows Media Player and VLC media player.
The correct thumbnail from youtube is only correctly displayed for the file where I used --write-thumbnail to download the thumbnail and mkvpropedit to embed the thumbnail.
For the file where I used the --embed-thumbnail option to download and embed it directly, either no thumbnail is being displayed or one is generated from the video.

@ghost commented on GitHub (Aug 25, 2016): I mainly use a software called Icaros which enables MKV files showing thumbnails in windows explorer using the thumbnail inside the file or, if there is no thumbnail inside it, using a generated one. But I see the same thing with Windows Media Player and VLC media player. The correct thumbnail from youtube is only correctly displayed for the file where I used --write-thumbnail to download the thumbnail and mkvpropedit to embed the thumbnail. For the file where I used the --embed-thumbnail option to download and embed it directly, either no thumbnail is being displayed or one is generated from the video. ![Screenshot](https://cloud.githubusercontent.com/assets/21064133/17974159/3cfaafcc-6ae5-11e6-92ab-8f1a4b399a90.png)

deekerman commented

2026-02-21 04:23:32 -05:00

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@u1735067 commented on GitHub (Nov 4, 2017):

Hi, you might be interested in merging https://github.com/Alex131089/youtube-dl/compare/Alex131089-mkv-thumbnail or https://github.com/Alex131089/youtube-dl/compare/Alex131089-mkv-thumbnail-filename, I was able to embed thumbnail without issue in VLC or MPC-HC with this.
The second branch tries to respect the filename convention (there's no orientation check nor dimensions enforcement/conversion), but using another/video's filename works too, at least in VLC.
I guess this would fix #6046 ?
Thanks for this utility :)

@u1735067 commented on GitHub (Nov 4, 2017): Hi, you might be interested in merging https://github.com/Alex131089/youtube-dl/compare/Alex131089-mkv-thumbnail or https://github.com/Alex131089/youtube-dl/compare/Alex131089-mkv-thumbnail-filename, I was able to embed thumbnail without issue in VLC or MPC-HC with this. The second branch tries to respect the [filename convention](https://matroska.org/technical/cover_art/index.html) (there's no orientation check nor dimensions enforcement/conversion), but using another/video's filename works too, at least in VLC. I guess this would fix #6046 ? Thanks for this utility :)

deekerman commented

2026-02-21 04:23:32 -05:00

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@yan12125 commented on GitHub (Nov 4, 2017):

Awesome! Does it support non-ASCII thumbnail filenames? And I wonder how accurate guess_type is.

@yan12125 commented on GitHub (Nov 4, 2017): Awesome! Does it support non-ASCII thumbnail filenames? And I wonder how accurate ```guess_type``` is.

deekerman commented

2026-02-21 04:23:32 -05:00

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@u1735067 commented on GitHub (Nov 4, 2017):

Awesome! Does it support non-ASCII thumbnail filenames?

No idea, but as much as for the MP3 I guess.

And I wonder how accurate guess_type is.

Mimetypes module seems to rely on the extension, so it's very "light".

And with only 2 extensions recognized by the convention, I came with this much simpler version : https://github.com/Alex131089/youtube-dl/tree/Alex131089-mkv-thumbnail-simpler.
For other filetypes, you'd still need mimetype detection.

@u1735067 commented on GitHub (Nov 4, 2017): > Awesome! Does it support non-ASCII thumbnail filenames? No idea, but as much as for the MP3 I guess. >And I wonder how accurate guess_type is. [Mimetypes module](https://docs.python.org/3/library/mimetypes.html) seems to rely on the extension, so it's very "light". And with only 2 extensions recognized by the convention, I came with this much simpler version : https://github.com/Alex131089/youtube-dl/tree/Alex131089-mkv-thumbnail-simpler. For other filetypes, you'd still need mimetype detection.

deekerman commented

2026-02-21 04:23:32 -05:00

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@grenzor commented on GitHub (Dec 16, 2017):

This looks good, any reason it isn't merged yet?

@grenzor commented on GitHub (Dec 16, 2017): This looks good, any reason it isn't merged yet?

deekerman commented

2026-02-21 04:23:32 -05:00

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@srussel commented on GitHub (Jul 20, 2018):