Used Avidemux to edit video, resulted in 2x higher bitrate?

[videoconverter11]

Hi everyone,

I used Avidemux to take out a 10 minute portion of a 2 hour long - 24 GB avi file I have. The original 2 hour long file had a Total Bitrate of 30513 kbps, a frame rate of 29 frames/sec. After using Avidemux, where the settings I used was "copy", my 10 minute portion of the video now has a Total Bitrate of 64000 kbps. Does anyone know why this is? Thanks!

[hech54]

So you used:
COPY(video)
COPY(audio)
AVI (in the drop-down box) ?

Did you get any warnings about cutting on key frames or any other "frame" warnings?

[videoconverter11]

Hi, yes, that is exactly what I did, the drop-down box said AVI muxer, but I think its the same thing. I didnt get any warnings, which makes me wonder if I messed up on a setting somewhere...

[Baldrick]

Can you post the full details of the avi? Use mediainfo (view->text) or mediainfoxp.

[hech54]

Hi, yes, that is exactly what I did, the drop-down box said AVI muxer

Avi muxer ?

I've never seen that on any of my versions of AviDemux.

[Baldrick]

Yep. Under output it says AVI Muxer. At least in version 2.6.

[hech54]

Yep. Under output it says AVI Muxer. At least in version 2.6.

I see said the blind man. Good to know. I don't upgrade unless something is broken.

[jagabo]

It's entirely possible that your sample has an average bitrate of 64 Mbps when trimmed and remuxed from a file with an average bitrate of 30 Mbps. If the source uses variable bitrate some parts will be encoded with more, some parts with less than the average. If you happened to pick out a section with lots of action, noise, etc. it will have a higher average bitrate.

It's also possible the software you're using to check the bitrate is wrong. Is the file size approximately correct for a 60 Mbps video? A 10 minute video at 60 Mbps should be about 4.5 GB. Try using Mpeg File Bitrate Viewer to check the bitrate and view a graph of bitrate.

[videoconverter11]

I just used bitrate viewer, and it says that the average bitrate is 28771 kbps with a peak of 28771 kbps. (this is with the original 2 hour long file)

the weird thing is, when I used bitrate viewer on the small trimmed file with the 60,000 kbps rate, it said something around 28,000 kbps.

where the 60,000 kbps came from was right clicking on the file -> properties -> details tab.

At this point I am not sure what is going on as windows reports something but bitrate viewer is doing another. any thoughts?

[jagabo]

Bitrate viewer isn't perfect. I've seen it mess up occasionally. But it's usually the most accurate at determining bitrates because it actually parses the entire file. Most programs just report what's in the header or estimate based on file size.

Since:

size = bitrate * running time

You can verify the bitrate by the file size. Of course the file includes audio and container overhead but with high video bitrates you can ignore that and come up with a reasonable estimate.