Fixing Partially Download MP4 Files

[pone44]

I occasionally download MP4 files and have the connection terminate in the middle of the download. You are left with a corrupted file that will not play in VLC. There are instructions online about using the VLC "Convert/Save" function to repair such files, but I have never had that work. VLC goes into an endless loop. Are there reliable utilities that will scan an MP4 for obvious damage and patch up the file to make it playable?

[LigH.de]

It depends on the structure of the MP4 file. If all the relevant header information was at the end of the aborted file, it is close to impossible to reconstruct them. Only MP4 files with header information at their beginning can be fixed by truncating them at a last clean position. Creating MP4 files with "fast start" structure requires either an already existing file or some efforts during the creation of a new file (like keeping most of its content in RAM until all important header details are known).

[pone44]

It depends on the structure of the MP4 file. If all the relevant header information was at the end of the aborted file, it is close to impossible to reconstruct them. Only MP4 files with header information at their beginning can be fixed by truncating them at a last clean position. Creating MP4 files with "fast start" structure requires either an already existing file or some efforts during the creation of a new file (like keeping most of its content in RAM until all important header details are known).

If the header information was at the start of the file, would it be playing as normal in any MP4 player (until the aborted end of file anyway)? How would I determine if the header is in good shape using MediaInfo?

From what I can tell, the header is being read by MediaInfo. The download froze on just the final part where the file is closed. So how would you repair such a file?

[davexnet]

See this info about the h264 moov atom.
https://www.adobe.com/devnet/video/articles/mp4_movie_atom.html

Some of the video repair utilities here at videohelp may help, but they all depend on a "good" file being available,
created with the same parameters; for example created in the same camera @ same settings as the damaged file

https://www.videohelp.com/software/recover-mp4-to-h264
https://www.videohelp.com/software/Video-Repair-Tool
https://www.videohelp.com/software/untrunc

[pone44]

See this info about the h264 moov atom.
https://www.adobe.com/devnet/video/articles/mp4_movie_atom.html

Some of the video repair utilities here at videohelp may help, but they all depend on a "good" file being available,
created with the same parameters; for example created in the same camera @ same settings as the damaged file

https://www.videohelp.com/software/recover-mp4-to-h264
https://www.videohelp.com/software/Video-Repair-Tool
https://www.videohelp.com/software/untrunc

When you say they depend on a "good" file, do you mean any file created from the same source, regardless of its size? What is the reason for that requirement?

Which of these utilities is the most complete?

[davexnet]

See this info about the h264 moov atom.
https://www.adobe.com/devnet/video/articles/mp4_movie_atom.html

Some of the video repair utilities here at videohelp may help, but they all depend on a "good" file being available,
created with the same parameters; for example created in the same camera @ same settings as the damaged file

https://www.videohelp.com/software/recover-mp4-to-h264
https://www.videohelp.com/software/Video-Repair-Tool
https://www.videohelp.com/software/untrunc

When you say they depend on a "good" file, do you mean any file created from the same source, regardless of its size? What is the reason for that requirement?

Which of these utilities is the most complete?

Yes regardless of it's size. They use the good sample as a template to rebuild the damaged file
Untrunc & recover-mp4 is CLI, free; Untrunc is Linux, but works from a 64 bit Live DVD if you want to try it.
Video-repair-tool has a basic GUI and will recover 50% for free if it is able to.

[blud7]

1. the "good file" approach by davexnet above is more suited to people who have lost data from a single source like he said e.g. a camera and you can use the "good file" to reconstruct your video.
2. If VLC won't play it at all, it is unlikely it can be recovered by any other methods besides the good file approach. You can try opening it using mkvmerge and remuxing to an mkv. Barring this the file is lost.

[pone44]

1. the "good file" approach by davexnet above is more suited to people who have lost data from a single source like he said e.g. a camera and you can use the "good file" to reconstruct your video.
2. If VLC won't play it at all, it is unlikely it can be recovered by any other methods besides the good file approach. You can try opening it using mkvmerge and remuxing to an mkv. Barring this the file is lost.

What would be the commands to open using mkvmerge and remux to mkv format?