Recovering a corrupted AVI from a digital camera

[debest]

So I'm taking pictures of my daughter's performance on stage with my Canon S1 IS, and I switch over to movie mode to record her singing a song, which is immediately followed by another. I shoot these as a single, continuous movie, with the camera set to 640x480 and 30fps. The normal format for video files from this camera is a "RIFF" video within an AVI container.

About half-way into the second song (about 4-5 minutes of recording), the recording abruptly stops and I am presented with the dreaded Canon "E18" message. This has happened once before, but I didn't really care that time. Thankfully, I can shut the camera down and restart with no other apparent ill-effects.

I try to replay the movie: the camera presents "Unidentified file" (or words to that effect). I copy the files off the card to my computer and I've got an AVI file, about 450MB in size, that WMP won't play, either. Neither can VirtualDubMod open it: when I try to open it, the VirtualDub Error box says "Cannot detect file type of (filename).AVI". (BTW, VirtualDubMod has no problem opening video files from this camera when my camera doesn't crash.)

I would dearly love to be able to recover this file, if only for the first song. Has anyone experienced this before, and are there any tools that may be able to retrieve my movie? There seem to be a bunch of shareware tools that can be found by Google, but I've heard of none of them and I really don't like installing random crapware on my machine. Just trying to separate the wheat from the chaff, you know? Thanks!

[aedipuss]

first - your camera doesn't shoot in "riff" video format. there is no such thing. it shoots in motion jpeg format. a riff is a type of file header if you need to know.

second - if it's listed in the tools section here then it isn't crapware.

third - start at the top of the list in the tools section/video-repair/ if it can be fixed one of those tools will most likely do it. start with just the free ones. like the first one on the page looks promising.

[ropdoh]

Try opening the video file in a Hex editor. If all you see are 00s, then the file doesn't contain any data, and you aren't going to be able to recover anything.

Try: HxD, its freely available from http://www.mh-nexus.de/

Its worth a quick check to ensure you don't waste too much time trying to recover the video if there truly is no data in the file.

[debest]

ropdoh, the first several hundred bytes of the file are 00, but then the remaining is looking "data"ish. ''

aedipuss, thanks for the clarifications, and for guiding me to the tools section (which I had not seen). I tried the Digital Video Repair utility, and it came back with "Unknown or not Supported Format" when I tried to load the file. The rest of the tools don't appear to be suited (DivX, Xvid, DVD, etc) to my format of video.

Just for fun, I made a copy of the file, then deleted all the 00 entries at the beginning of the file, hoping against hope that would do something. Alas, as expected, the results were identical.

Do you think that my video data is there, and can it be recovered?

[guns1inger]

I would try to open the file with VLC. It has been designed to read partial and damaged files, and may be able to play back any undamaged portions. If it can find any content that it can play, you can use the streaming function (File -> Wizard for the simplified version) in VLC to transcode this to a new file.

[debest]

guns1inger, thanks for the idea. Actually, I tried VLC yesterday. I got "odd" results: no error messages on opening the file, but when it played the file I got a 5-6 second long playback of silence and no video window.

Then, just for kicks, I tried the copy where I deleted out the blank bytes (see earlier in thread). It refused to open, saying "unrecognized file" or something.

Am I looking at something more "forensic" to do this?

[aedipuss]

if you want to play around you could try taking the header out of a known good video and pasting it into the bad file with the hex editor. the header is how a video file is identified by programs. no guaranty of any results. the file may still be totally blank.

[debest]

How many bytes is the header of a "good" video file? Is it custom to this camera, or do motion jpegs all have the same format. Forgive my ignorance, this is all technically over my head. Thanks.

[aedipuss]

heh. do you know what a byte is? sorry, had to ask. take a look at a couple of known "good" files. compare the first portion of text and see how far they are the same. copy that portion to the bad one and give it a shot. i'm not optimistic but who knows......

p.s - it's 4 bytes long

[debest]

I presume that in hex a byte is 2 characters long. Therefore, you are saying that the header would be 8 characters (4 groups of 2 characters) long? And that these should be the very first 8 characters of the file? Thanks.

Darren Best

[guns1inger]

The header could be many bytes long. You will have to look at the information in the file and try to make a determination.

[debest]

Okay, I examined the first several dozen lines of the data in some "good" files made by this camera. The hex editor includes an ASCII translation. Some was english-readable, some not. Most of the information was identical from file to file, but some was not (owing likely to different lengths of clips, date stamps, etc.). Here's an example from one:

RIFF..{.AVI LIST
F...hdrlavih8...
5‚..Œ1$.........
Í............/..
€...à..........
.........LISTt...
strlstrh8...vids
mjpg............
5‚..@B......Í...
./...'..........
€.à.strf(...(...
€...à.......MJPG
................
....LIST\...strl
strh8...auds....
................
"V......“D..D¬..
.'..............
strf........"V..
D¬......IDIT....
MON DEC 24 15:15
:39 2007..LIST..
..INFOISFT....Ca
nonMVI02..JUNK~.

This was followed by several hundred blank bytes, then (presumably) the "movie"

I copied over verbatim the above data from one of the "good" files, plus the blank bytes, and pasted it into the front of my damaged file. I fired up VLC, and it said that it was corrupted and offered to repair it (progress!). The "repair" took a nano-second, then started to play. No video window, but I heard about one second of the audio! Then all that comes out is white noise static. Also, VLC seems to think that the file is 10hours, 24minutes, and 19seconds long! Huh?

I'd like to think that my movie is still there. But, I just don't know the "language" of the headers. Can anyone link me to anywhere that explains this for Canon cameras (or AVI files in general)? My quick Google search turned up nothing obvious, but then I don't really know what I'm looking for.

Thanks again for all the help!

[mech001]

dear friend

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