Bluesky videos downloaded using cobalt.tools fail to be uploaded onto Discord on Android 15

[GreenSwede]

bug description

Videos that have been downloaded using cobalt.tools cannot be initialized properly when attempting to upload said video file onto Discord. Discord reports "Upload Failed. File cannot be empty". The video timeline length also reports 0:00 which hints at an issue. The video file can be played on my Android device without issues and the video file is not empty. The same video file from Bluesky can be downloaded using cobalt.tools from Firefox on my Linux PC, and uploading it onto the Linux Discord PC client works as expected - no errors.

Comparing the SHA1 hash of the downloaded video file between Android and PC shows that they are identical, so there are no differences in the files. Attempting to upload the video that was downloaded from my Linux PC onto my Android phone still gives me the same error on Discord, so it appears that the video file is fine but Discord on Android doesn't accept it. I do not have an iOS device to test this on, in case this is a general mobile bug on Discord's side.

Other videos that I have gotten from other websites or Discord itself can be uploaded onto the Android version of Discord just fine, only cobalt.tools videos show this issue. I can confirm that the same Bluesky video that I tested will be accepted by Discord on Android when it has been downloaded using the F-Droid Seal app (yt-dlp is used by the app).

reproduction steps

1. Download Bluesky video clip using cobalt.tools from Android device or PC (tested with Google Chrome and Firefox)
2. Attempt to upload the video file to a Discord server/DM on Android
3. Be met with "File cannot be empty" error and a 0:00 timeline length in the file explorer.

screenshots

links

platform information

Android 15 (Sony Xperia 1 VI)

additional context

Tested downloads on Google Chrome 141.0.7390.122 and Firefox 144.0.1