I am trying to convert some "raw" webcam footage which I believe is mjpeg format. The only video editing software that I have been able to find that can recognize the file I am trying to convert is Videopad Professional by NCH Software. The file loads into the editor, but the problem is it plays back way too fast, and appears to be missing a lot of frames. Also, the audio is not recognized by the editor.
The video file I am trying to convert is over 60 GB in size, and is actually a .tmp file which I have renamed the file extension to .mjpeg in order to get the editor to even recognize it. The .tmp file is all that was left behind by the Logitech Webcam Software application running on Win 7 after the computer crashed while capturing footage from a Logitech c615 webcam.
From what I am able to gather, the webcam captures video according to the UVC protocol, which I am trying to become more knowledgeable about. I believe there is more than one possible format a UVC webcam can use, but I cant seem to find out what format this specific webcam really uses for video and audio prior to the Logitech Webcam Software encoding it to a wmv file after recording is stopped properly by the normal means. Since one possible format is mjpeg, I tired renaming the .tmp file to a .mjpeg extension which seems to kind have worked (except the video plays too fast and audio is lost), but I am not sure that is what I should really be doing to try to recover the footage.
I am somewhat new to video conversion, so any help anyone can offer would be greatly appreciated.
Thanks in advance for any advice on this.
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I tried that already, unfortunately, doing so gives me nothing but the file size.
Even with a known good file?
Perhaps you should contact Logitech to see if they have any advice. I just realized a "known good file"
would probably have been saved as a WMV - I've made videos from a Logitech webcam, I don't remember there being
much of a delay between the time you stop the recording and the appearance of the WMV file -
suggesting the "raw" file must be very close to the finished file. ie. it wasn't re-encoded
Last edited by davexnet; 11th Dec 2019 at 21:54.
Its not corrupt, like I said I am able to get the file to load successfully into a video editor, it just plays back too fast and effectively is at a very low frame rate if slowed down (missing frames). What I am looking for help on is understanding the UVC format better, especially how audio is recorded by a webcam like this that takes nearly as long to re encode a completed recording that is stopped normally to WMV/WMA format as the original recording duration was?
What other codecs could a UVC compliant webcam be using on a hardware level to initially apply compression to the output stream? Mjpeg I believe is one, but what others could it possibly be using? And how about audio? I have been able to get the file to load into an editor simply by renaming the file extension to .mjpeg, so I am wondering what other file extensions could I try that may allow the file to playback at the correct speed and not be missing frames, as well as hopefully having the audio stream also?
BTW, the computer crashed while it was in the middle of the lengthy re-encoding process to WMV, so it did actually create a partial length duration WMV file which plays back at normal speed and frame rate, and has audio. So, I am sure the data is there in the .tmp file, I just don't know how to convert it correctly. Would it be possible to perhaps analyse the .dll file that the webcam software uses to re-encode the .tmp file to WMV to tell me how I need to re-encode it properly like the webcam software would have done if the computer hadn't crashed while it was in the middle of re-encoding?
Logitech has been of zero help. If no one on this forum is familiar with how these webcams work and can't offer me any advice, no problem, I was just hoping someone might.
Thanks for the responses thus far.
Uvc webcams are NOT vfr, as that hasn't been part of the spec. The apps that control & capture them may be making them vfr, however.
Not sure why you still don't get the bit about the long converting time, as I mentioned why in that other thread. Total re-encoding.
Again: uvc uses either uncompressed rgb or yuv (4:4:4 or 4:2:2 or possibly 4:2:0), or mjpeg, or mpeg2, or avc. They may have recently added hevc to that, but haven't checked the spec lately.
Audio may be other codecs but it is unlikely. Though mp3 and aac are probably options, the vast majority send out lpcm (possibly adpcm too). Most have single mics, so mono.
Sounds like you should have mjpeg vid & lpcm aud in that stream, so it's more a matter of picking framerates&rez, and samplerates&bitdepths, and figuring out packet frame sizes and cadence.