Transcoding to xvid creating huge files

[jmontana]

So for a while I was using the nightly encoding feature to create xvid files using the stock ffmpeg settings. These were taking my 1.9 GB MPEG files and creating avis that were about 600 MBs or so. This was great, but the problem was the fixed bit rate was causing issues when lots of action would happen.

After reading some other posts, I decided to try using -qscale instead of -b. With a -qscale setting of 6, I get great quality, but the file sizes are still too big, anywhere from 800 MBs to 1.1 GBs.

In one case, it generated a 3.1 GB file from a 1.9 GB MPEG!

I tried using -sameq instead of -qscale, but that created a file that was at least as big as the source.

So clearly, something is wrong. Can someone take a look at this setting and tell me if I'm doing something wrong? How can I get smaller file sizes?

Code:

<Conversion name="XviD" cmd="-y -i {SOURCE_FILE} -f avi -ab 224 -ac 2 -acodec mp3 -deinterlace -vcodec xvid -qscale 6 -vtag XVID {DEST_FILE}" targetExtension=".avi" />

Also, I'm viewing all of this on an SDTV, so I don't know if I need to specifically tell ffmpeg to use a 4:3 aspect ratio or not.

Thanks!

[sub]

Try a smaller qscale value. A qscale setting of 6 could give particularly large files.

[jmontana]

Try a smaller qscale value. A qscale setting of 6 could give particularly large files.

Really? I thought the lower the qscale value, the higher the quality. So a value of 1 is the best quality with largest file size, and 30 is worst quality with lowest file size?

What's a good value to use? Or should I just experiment?

Thanks!

[HtV]

It seems JMontana is right. From the ffmpeg documentation:

To have a constant quality (but a variable bitrate), use the option '-qscale n' when 'n' is between 1 (excellent quality) and 31 (worst quality).

http://ffmpeg.mplayerhq.hu/ffmpeg-doc.html

[sub]

Sorry, a higher value then

[jmontana]

Sorry, a higher value then

Okay. thanks. Sounds like I should just keep upping the value until I get something that works. Just wanted to make sure I wasn't missing some other parameter.

BTW, is there an answer to my question about aspect ratio?

[sub]

Sounds like I should just keep upping the value until I get something that works.

Correct.

BTW, is there an answer to my question about aspect ratio?

If you dont specify any special command line parameters to adjust the aspect ratio, then it'll use the source aspect ratio.