avidemux doubles file size when doing copy only??

[ryoaska1]

I tried to cut about 25% out of an AVI file and noticed that while the original file was about 1.9GB, the cut file was over 3GB. It's an AVI, and I used the AVI Muxer in output format, and 'copy' for both the audio and video sections. I tried it again without cutting anything and the file was about double in size. Why would it do this- copy means it doesn't re-encode so it should be (roughly) the same right?

EDIT:
Used MediaInfo and found that the larger sized file has a much higher 'overall bitrate'- about 20 Mb/s more. I'm not sure how to tell what coded the original uses or how to make avidemux/virtualdub use the same, is that the issue? Both the original and copied files have a "First video stream" of about 35 Mb/s which is almost exactly the 'overall bitrate' of the copy.

[ryoaska1]

I got the same results in virtualdub with both audio/video set to direct stream copy ... I had to install ffdshow and activate M-JPEG decoding to get virtualdub to even read the file, I don't know if that's useful info or not.

[jagabo]

It sounds like there is something wrong with your source file that's causing programs to misinterpret the length.

[hech54]

I tried to cut about 25% out of an AVI file and noticed that while the original file was about 1.9GB, the cut file was over 3GB. It's an AVI, and I used the AVI Muxer in output format, and 'copy' for both the audio and video sections. I tried it again without cutting anything and the file was about double in size. Why would it do this- copy means it doesn't re-encode so it should be (roughly) the same right?

You didn't cut on a key frame?

[jagabo]

I'm not sure about AviDemux, but VirtualDub in Direct Stream Copy mode will move the cut to a keyframe when you save.

Any chance you have two consecutively numbered file names as the input? Like File0001.AVI and File0002.AVI? VirtualDub FilterMod can be set to automatically append such files. Check the running time of the output file. Is it longer than the input file. Play the input and output files side by side. Do they match (aside from your cuts)?

[poisondeathray]

But if it was mjpeg, every frame is a keyframe. And it doesn't make sense because vdub has an internal mjpeg decoder, you shouldn't need to install ffdshow just to decode. So something doesn't seem right

Open the original in mediainfo (view=>text) and post the report back here

[jagabo]

it doesn't make sense because vdub has an internal mjpeg decoder, you shouldn't need to install ffdshow just to decode.

Maybe it used a fourcc that VirtualDub's internal decoder didn't recognize?

On the other hand, 1.9 GB is pretty small for an MJPEG video.