Restoring lost THM file for an AVI

[barneagle]

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?

[simonaward]

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?

[barneagle]

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.

[barneagle]

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

[d10jedijonze]

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

[Simon_Gardner]

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