Will I be able to save this corrupted MKV file? A sad history... :(

[JamesPT]

Hi guys, first post here, thank you in advance for your help

I'm trying to save an one hour online meeting recorded with OBS on Windows 10. The output was a perfect working MKV file (I didn't record screen image, only audio, so the screen was intentionally black).

Everything was working fine with the file (I was able top play it using VLC) until I had the incredible idea of extracting the audio to send it to an audio to text tool (long meeting I prefer reading instead of listening).

I made the terrible mistake of converting the audio track to MP3 using VLC built in tool, outputing the file to the same folder as the original MKV file (which I haven't backup). Even the name of the file I left the same, and I think this was my biggest mistake here.

VLC started converting to MP3 and ended up overwriting the original file and VLC started showing an error dialog while converting ("The output file already exists. If the recording continues, the file will be overridden and its content will be lost") and left me with only two options: Overwrite or Keep existing file. At this point, it doesn't matter if I click on 'Overwrite' or 'Keep existing file', the message box keeps coming back, infinitely (obviously I clicked multiple times "Keep existing file" as I realized how dumb I was). The only way out was to start up Task Manager, and force Windows to end the task, which I did and VLC was closed.

I ended up with a MKV file that won't play on VLC (or any other player, even MKV file player) and the original file was gone/overwritten.

Tried to restore the original file using System Restore. I was able to access the original file but it seems that even the original file was damaged as I can't play it, nor open it using MKVToolnix (and many other tools related to MKVToolnix, they all say the file is not MKV...). Trying to open the original file on MKVToolnix I got an error message saying that "No EBML head found. This file is probably not a Matroska file." It is very strange since the original file has the creation date exactly at the time as the meeting ended (and I ended the record on OBS), but it seems to be corrupted I don't know why...

I'm really desperate as this meeting was very, very important.

If I only could save the audio track I'd be the happiest man on earth.

Is there something I can do to save/extract the audio track?

EDIT: Here's the original MKV file, recovered from Windows System Restore but damaged as well: https://www.dropbox.com/s/o4p56vugyujren7/reuniai-miamoto-2020-08-17%2008-11-12.mkv?dl=0

Thank you guys

[jagabo]

Does MediaInfo give you any useful information about the file? Try moving the file elsewhere and restoring it again. Any difference?

[davexnet]

Tough lesson ..;. Have you tried any undelete tools such as Recuva?

It seems unlikely VLC actually overwrote the original in place, but it's possible

If the new file was an mp3 and the old mkv, how did it overwrite it ? Different file extension .

[JamesPT]

Does MediaInfo give you any useful information about the file? Try moving the file elsewhere and restoring it again. Any difference?

Unfortunately no. Format, Video_Format, Audio_Format and Text_Format columns are all empty. If a load another MKV file the colums are filled with correct info.

What do you mean by moving the file elsewhere? Other PC or Mac? I've tried moving (copying original file) to desktop with no luck, file won't play. Thank you anyways!

[JamesPT]

Tough lesson ..;. Have you tried any undelete tools such as recuvu?

It seems unlikely VLC actually overwrote the original in place, but it's possible

If the new file was an mp3 and the old mkv, how did it overwrite it ? Different file extension .

Hard lesson indeed. Now I will backup before try converting (feeling such a dumbass for not doing it before).

Yes I've tried Recuva (don't know if is the same thing you mentioned). I was able to restore the original file but even this file can't play anywhere and isn't recognized as a MKV file. As I remember the original file has the exactly same size in the restore as the file before converting (on the other hand the converted file by VLC had 0 byte size).

It overwrote because VLC gave me the default option of saving the name of the file as the same name of the original file, and it didn't append .mp3 at the end of the file name (resulting in file.mkv.mp3 as I thought), it simply tried to save to file.mkv as mp3 without .mp3 extension.

Thank you anyway my friend

[jagabo]

What do you mean by moving the file elsewhere? Other PC or Mac?

I mean move the file to another folder so that it doesn't exist at its current (original) location. Then restore the file from your backup.

But I was able to duplicate your situation with Media -> Convert... in VLC. It results in a zero length file. Most programs won't let you do this because they open the source file for reading first, then open the output file for writing -- normally Windows won't let you open a file for writing if it's already open for reading -- to prevent exactly what's happened here.

There's no way you'll ever get anything out of a zero length file. Your best hope is to restore the file from a backup. System Restore may or may not restore the original file (it doesn't backup everything).

[JamesPT]

What do you mean by moving the file elsewhere? Other PC or Mac?

I mean move the file to another folder so that it doesn't exist at its current (original) location. Then restore the file from your backup.

But I was able to duplicate your situation with Media -> Convert... in VLC. It results in a zero length file. Most programs won't let you do this because they open the source file for reading first, then open the output file for writing -- normally Windows won't let you open a file for writing if it's already open for reading -- to prevent exactly what's happened here.

There's no way you'll ever get anything out of a zero length file. Your best hope is to restore the file from a backup. System Restore may or may not restore the original file (it doesn't backup everything).

Thank you for your time replicating the issue. Unfortunately VLC (and my lack of attention) let this happen.

I'm intrigued why the original file (recovered with Recuva and System Restore Explorer) is damaged altough it has the same size as the original (167Mb) and creation date is the same day/time as the meeting finished... I know I won't be able to play this file but if it was possible to extract only the audio track it'd be awesome. The first thing I did was move the file to another partition on the same machine, without success in reading/playing it. I'm losing my faith on this

[jagabo]

Open your file in a hex editor. Is it full of zeros?

[davexnet]

Upload the file here to the forum, somebody can check further.

I also did jagabo's test and I'm quite surprised VLC wrote over a file that was active as input.
Sloppy programming

[JamesPT]

Upload the file here to the forum, somebody can check further.

I also did jagabo's test and I'm quite surprised VLC wrote over a file that was active as input.
Sloppy programming

Here's the original MKV file (recovered from the System Restore, but damaged as well):
https://www.dropbox.com/s/o4p56vugyujren7/reuniai-miamoto-2020-08-17%2008-11-12.mkv?dl=0

Thank you

[JamesPT]

Open your file in a hex editor. Is it full of zeros?

Yeap full of zeros, attached a screenshot to this reply so you can see. Thanks

[jagabo]

The file is mostly zeros. There's a tiny bit data here and there but I doubt you'll ever get anything useful out of it.

Do you have a backup other than "System Restore"?

[JamesPT]

The file is mostly zeros. There's a tiny bit data here and there but I doubt you'll ever get anything useful out of it.

So basically VLC overwrote the original file when trying to convert and somehow it affected the backup file (created and modified before the event). How the backup file ended up with the same size as the original, but with no useful data?

[jagabo]

I don't think System Restore actually backs up user files. Just some information about them. What version of Windows are you running?

[JamesPT]

I don't think System Restore actually backs up user files. Just some information about them. What version of Windows are you running?

Windows 10

[jokster]

i would reckon the file is history but you could try R-Undelete (free)
is top notch at file recovery

https://www.r-undelete.com/

[jagabo]

It's virtually impossible that VLC mangled your backup. The file was probably bad before it was backed up. Or wasn't restored properly. Or was mangled again after restoration.

I'm not really familiar with how Win10 backs up files. But check this process:

https://support.microsoft.com/en-us/help/4027408

That reminds me -- I built the computer I'm using now a few months ago and haven't yet configured the backup settings!

[butterw]

I overwrote a file a couple months back in a manner not dissimilar to the OP. It's a sad but familiar story.

I wouldn't recommend using VLC video player for re-encoding.

[davexnet]

Not sure if the OP added a post on the VLC forum, but I left a comment
asking if a safeguard could be added, VLC should not attempt to write to a file it has open for Input.
However, I'm not a Windows programmer, there may be nuances to the situation I'm not aware of

I tried a similar operation in Virtualdub2, after ignoring the warning that I was overwriting an existing file,
this came up and the original file was not touched

[JamesPT]

Finally made some progress!

I was able to recover a (not working yet) file which is not full of zeros and opens on MKVtolnix, altought I'm not being able to play it anywhere, nor convert the audio track to mp3 (when I try to convert using command line I get the "Error: Failed to create the file 'reuniao.mp3': 0 (open file error)" message.)

Refered file is here: https://www.dropbox.com/s/20i85qje7o7vlr0/reuniao.mkv?dl=0

Also tried Meteorite and other video recover/repair tools without success...

Here's MKVToolnix info about the file:
+ EBML head size 40 data size 35
|+ EBML version: 1 size 4 data size 1
|+ EBML read version: 1 size 4 data size 1
|+ Maximum EBML ID length: 4 size 4 data size 1
|+ Maximum EBML size length: 8 size 4 data size 1
|+ Document type: matroska size 11 data size 8
|+ Document type version: 4 size 4 data size 1
|+ Document type read version: 2 size 4 data size 1
+ Segment: size 171922744 size 171922756 data size 171922744
|+ Seek head (subentries will be skipped) size 72 data size 67
|+ EBML void: size 148 size 157 data size 148
|+ Segment information size 80 data size 75
| + Timestamp scale: 1000000 size 7 data size 3
| + Multiplexing application: Lavf58.29.100 size 16 data size 13
| + Writing application: Lavf58.29.100 size 16 data size 13
| + Segment UID: 0xa2 0xc6 0xfe 0xaa 0x80 0xf9 0xa8 0x36 0x04 0x10 0xe0 0x91 0x7b 0x7a 0x96 0x25 size 19 data size 16
| + Duration: 00:59:55.534000000 size 11 data size 8
|+ Tracks size 238 data size 232
| + Track size 133 data size 124
| + Track number: 1 (track ID for mkvmerge & mkvextract: 0) size 3 data size 1
| + Track UID: 1 size 4 data size 1
| + Lacing flag: 0 size 3 data size 1
| + Language: und size 7 data size 3
| + Codec ID: V_MPEG4/ISO/AVC size 17 data size 15
| + Track type: video size 3 data size 1
| + Default duration: 00:00:00.016666666 (60.000 frames/fields per second for a video track) size 7 data size 3
| + Video track size 21 data size 12
| + Pixel width: 1920 size 4 data size 2
| + Pixel height: 1080 size 4 data size 2
| + Display unit: 4 size 4 data size 1
| + Codec's private data: size 56 (H.264 profile: High @L4.2) size 59 data size 56
| + Track size 93 data size 84
| + Track number: 2 (track ID for mkvmerge & mkvextract: 1) size 3 data size 1
| + Track UID: 2 size 4 data size 1
| + Lacing flag: 0 size 3 data size 1
| + Name: simple_aac_recording size 23 data size 20
| + Language: und size 7 data size 3
| + Codec ID: A_AAC size 7 data size 5
| + Track type: audio size 3 data size 1
| + Audio track size 26 data size 17
| + Channels: 2 size 3 data size 1
| + Sampling frequency: 44100.0 size 10 data size 8
| + Bit depth: 16 size 4 data size 1
| + Codec's private data: size 5 size 8 data size 5
|+ Tags size 204 data size 198
| + Tag size 56 data size 46
| + Targets size 10 data size 0
| + Simple size 36 data size 26
| + Name: ENCODER size 10 data size 7
| + String: Lavf58.29.100 size 16 data size 13
| + Tag size 68 data size 58
| + Targets size 14 data size 4
| + Track UID: 1 size 4 data size 1
| + Simple size 44 data size 34
| + Name: DURATION size 11 data size 8
| + String: 00:59:55.534000000 size 23 data size 20
| + Tag size 68 data size 58
| + Targets size 14 data size 4
| + Track UID: 2 size 4 data size 1
| + Simple size 44 data size 34
| + Name: DURATION size 11 data size 8
| + String: 00:59:55.494000000 size 23 data size 20
|+ Cluster size 198507 data size 198500

[ProWo]

No chance.

[JamesPT]

Thank you anyway guys. Lesson learned the hard way. Won't use VLC to convert and will always backup before doing anything. Still a mistery how even the backup was damaged to the point of not opening...

[jagabo]

How did you "recover" that file? It does have a valid mkv header and a little useful data. But it has lots of stuff that's not audio or video. You can see lots of plain text (8 bit and 16 bit) in many places throughout the file. It looks to me like something from an file undelete program. Those usually don't work well with video files because large files are often not contiguous (the data can be spread over many areas of the disk) and undelete programs usually assume contiguous files (other than the first cluster they have no easy way of figuring out what clusters were once occupied by the file). If this is your boot drive and you've been using it all this time you've greatly increased the possibility that Windows has overwritten parts of the drive where the video file once was. So your chances of getting even partial results is decreasing minute by minute.

[JamesPT]

How did you "recover" that file? It does have a valid mkv header and a little useful data. But it has lots of stuff that's not audio or video. You can see lots of plain text (8 bit and 16 bit) in many places throughout the file. It looks to me like something from an file undelete program. Those usually don't work well with video files because large files are often not contiguous (the data can be spread over many areas of the disk) and undelete programs usually assume contiguous files (other than the first cluster they have no easy way of figuring out what clusters were once occupied by the file). If this is your boot drive and you've been using it all this time you've greatly increased the possibility that Windows has overwritten parts of the drive where the video file once was. So your chances of getting even partial results is decreasing minute by minute.

The file recovered with System Restore Explorer (which mounts a fake partition with old versions of the files) was not even opening on MKVToolnix. It was full of zeros as I mentioned a few posts back.

I then used R Undelet to recover the latest file (posted today along with it's MKV info), which had EBML header "preserved" but wasn't playing, able to be converted or have it's audio track extracted.

Is there another way I can try to recover the original file?

[butterw]

Overwritting the source file is not a bug but a feature, according to a vlc dev: https://forum.videolan.org/viewtopic.php?f=14&t=153993

But obviously if for any reason (including vlc bugs) the conversion fails, your source file is partially overwritten and thus very likely unrecoverable.

[davexnet]

Overwritting the source file is not a bug but a feature, according to a vlc dev: https://forum.videolan.org/viewtopic.php?f=14&t=153993

But obviously if for any reason (including vlc bugs) the conversion fails, your source file is partially overwritten and thus very likely unrecoverable.

I responded to that, I asked them if there was a valid scenario in VLC where such as situation is used