Why do RM files become so bloated when converting to Flash?

[flguy]

I am using Mencoder by command line to automatically convert RealMedia (.rm) files to Flash (.flv). How come the Flash file becomes so huge after converting RealMedia? The video quality is just fine, but the file bloat is crazy.

For example, my original .rm source is 4Mb, but after conversion to .flv it is now 24Mb. Even an 18Kb test file gets blown up to 94Kb, so we are talking 4-8x's the file size depending.

This is my argument string in case it helps:
-of lavf -oac mp3lame -lameopts abr:br=56 -srate 22050 -ovc lavc -lavcopts vcodec=flv:vbitrate=300:mbd=2:mv0:trell:v4mv:cbp:l ast_pred=3 -vf scale=320:240

I do not have this trouble with any other file format. In fact, all other file formats turn out to have a much smaller .flv file (using the same argument string as above).

By the way, this needs to be an automated processes so I CANNOT use any client converter programs (I know they are a dime a dozen).

Thanks for any insight.

[Baldrick]

Does it change if you lower the bitrate?
Or maybe something wrong with the runtime, have you tried play it and see if it's longer than the original?

[flguy]

Lowering the bit rate does not solve the file bloat problem. I think it has something to do with the way .rm files are created that .flv cannot handle properly, even though the video length and quality are just fine.

There is a third-party tool from SoThink media and they have a file upload demo site. You can upload a .rm and see the results for yourself once it converts to .flv: http://flashvideo.sothinkmedia.com/flash-video-encoder-command-line/aspnet-demo/upload.aspx

I'm attaching a file of the mencoder output for one of my .rm files that was 4Mb to start with and got blown up to 24Mb as an .flv. Maybe it will provide someone with insight.

I am just an end user, not a video expert. I think I am looking for a "theory" on why this is happening more than a fix, because I have a feeling a fix is not possible (please prove me wrong!).

Thanks.

rm-to-flv-mencoder.log

[flguy]

Anyone?? I am open to theories I can research, as well as fixes! Just don't know where to go from here. Thanks.