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FORUMS Canon Cameras, Lenses & Accessories Small Compact Digitals by Canon
Thread started 06 Apr 2005 (Wednesday) 01:56
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Restoring lost THM file for an AVI

 
barneagle
Hatchling
3 posts
Joined Apr 2005
Apr 06, 2005 01:56 |  #1

We've lost the THM file which accompanied the AVI file for one of our videos and we have realised that the camera does not recognise the existence of an AVI unless there is a THM to go with it.

We would like to be able to put videos back onto the camera from time to time because the camera provides an excellent portable viewing screen. (The display is far smoother, albeit much smaller, than the display on either of our PCs.)

I've discovered that the camera can be fooled into playing AVI #1 if I copy the THM file relating to a different video (AVI #2), then rename it to match the name of AVI #1. The camera seems to take the duration from the THM file, so if #2 is shorter than #1, the display of #1 is truncated. If #2 is longer than #1, we can watch the whole of #1 but the camera then gets confused.

Is there any way we can recreate a THM file that properly matches an AVI?




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simonaward
Junior Member
23 posts
Joined Apr 2004
Apr 07, 2005 04:20 |  #2

Which camera do you have?

I have used the technique you've described before with no problems using an old IXUS V. I couldn't remember ever doing this using my newer IXUS 400, so I've just had a go.

I took a very short video of a peice of paper with 'Test' written on, and then another longer video panning around the room. I then used a card reader and deleted the THM of the longer video and copied & renamed the THM of the shorter video.

The IXUS 400 played back the video fine! The only difference is when in preview mode and you zoom out to see multiple thumbnails, both videos had 'test' as their thumbnail.

From memory, the older IXUS V used the THM as the image to display when browsing through images/videos and you didn't see the real video until you pressed play. The IXUS 400 seems a bit smarter than that though, and does use the first frame of the video when browsing, and only the THM when in multiple thumbnail mode. It wouldn't display the video at all if you don't have a THM file.

Unfortunately my old IXUS V is dead (RIP), so I can't test it. Perhaps it did decide on the length of a video based on the THM (but this seems strange to me).

Out of interest, you say "If #2 is longer than #1, we can watch the whole of #1 but the camera then gets confused" - what do you mean by "confused"? What is it doing?




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barneagle
THREAD ­ STARTER
Hatchling
3 posts
Joined Apr 2005
Apr 08, 2005 11:21 |  #3

Hello Simon,

Thanks for your reply.

I'm sorry I used the rather vague expression "gets confused". What I meant was that the camera thinks that there is more video footage to come (because it's taking the duration from the THM file) but finds that it has reached the end of the video data in the AVI file.

I shall try to describe in more detail if movie #2 ( the one from which we have borrowed the THM file) is longer than movie #1 (the one whose THM file we have lost.)

When we turn the camera on and go into Browse mode the correct full-screen thumbnail is displayed. If we zoom out the incorrect small thumbnail (i.e. the thumbnail borrowed from video #2) is displayed.

When we play the video it plays correctly, but as soon as it reaches the end the display changes to show a small incorrect thumbnail (relating to video #2) in the centre of the screen with the words "Unidentified Image" underneath.

Originally I thought we had to turn the camera off and and on again to recover from this situation, but I now find that toggling to the thumbnail of the next or previous video, then back again, returns us to a full-screen display of the correct thumbnail.

From Browse mode we can go into Edit mode successfully, but as soon as we try to move to "Cut End" the display changes to show a small thumbnail of video #2 with "Unidentified Image" underneath.

In conclusion, the technique of borrowing the THM file from a longer video works up to a point, but results in the display of incorrect thumbnails, the inability to edit and the display of an error message when we play to the end of the video.

If there were a way of recreating a THM file that correctly matched the thumbnail(s) and duration of a video it would avoid these problems. It would be even better if a THM file could be created for an AVI file such as an edited video, since the edited video could then be displayed on the camera.




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barneagle
THREAD ­ STARTER
Hatchling
3 posts
Joined Apr 2005
Apr 08, 2005 15:50 as a reply to barneagle's post |  #4

Sorry. I should have mentioned that we have an Ixus 40.




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d10jedijonze
Hatchling
1 post
Joined Jan 2011
Jan 29, 2011 17:57 as a reply to barneagle's post |  #5

having the same issues myself - i want to replay video on my D10 for which I have deleted the thm files. Ie reinstall the videos to my camera from my laptop. I want to do this to by pass lenghthy rendering in premier pro 7. Also would be good for other reasons. I tried the method you did also but it does not seem to work for any length of video - shorter or longer.... CAN WE FIND A BIT OF SOFTWARE PLEASE CANON or someone TO RECREATE MISSING AND LOST THM'S..... PLEASE..... oh my files are MVI NOT AVI




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Simon_Gardner
Goldmember
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1,301 posts
Joined Mar 2010
Twitter @Simon_Gardner
Jan 31, 2011 07:17 |  #6

Stop deleting the tiny THM files? Just a thought...


@Simon_Gardner | Since 27 Nov 1987 | Tripod fetishist - moi?

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J5hort
Hatchling
1 post
Joined Aug 2017
Aug 16, 2017 11:17 |  #7

Pretty old thread, but found via Google search. Last post was not helpful as files may have been corrupt and lost. In my case the SD card was corrupt then I was able to restore with a disk utility. Some if the .THM files were missing or did not have the extra data on he files when restored resulting in the same undefined image when attempting to play back in camera. I am using Canon TX1.

As it turns out, the extra data associated with the .THM files do not seem to be specific. I think the extra data gets lost when copying file from Camera SD to PC. The file number seems to be what needs to match. So, I needed to get an THM file back that would work with a corresponding .AVI. Here is what I did. I had a MVI_1234.avi file and a corrupt MVI_1234.thm file on the SD card. I placed SD card in camera and took a short 1 second video. A new .avi and .thm were created (MVI_1235.avi and MVI_1235.thm). I presume that the new .thm has all the extra data as it was created by the camera. I then deleted MVI_1234.thm and renamed MVI_1235.thm to MVI_1234.thm effectively replacing a corrupt file with a good one. This appeared to have solved the problem as the undefined image error is no longer displayed.

Bad news is that I have a graduation video I am trying to transfer from the camera to mt DVR and it includes many, many corrupt .thm's that need to be fixed. But at least there is a solution. This should work to restore missing or lost .thm files.




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Restoring lost THM file for an AVI
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