Getting a 700MB avi and not less

[yonidass]

I've recently been backing up commercial DVDs (which I own) to MPEG4 avis, usually using the XVID codec. I follow all the steps in the Video_TS to DIVX guide, substituting the XVID codec. I go for the 700MB size and normally it works well, but every now and then a movie will be significantly less than 700MB. It still looks fine but if it's only 589MB then 700 should look that much better. I know this has to do with the difficulty of predicting video content and what not.

My question is, is there a way to ensure the final output is not significantly less than 700MB?

[thoughton]

Are you calculating your bitrate at all? Or just using the default number? I cant remember if the tutorial has a section on that or not (I think it does).

[yonidass]

Yes, I'm calculating the bitrate with the 'auto' option as per Major's tutorial. Also, I should have mentioned, I'm just doing a single pass encode.

[Case]

I'm just doing a single pass encode.

There you have it. Use two pass or three pass encoding. Note that the more accurate three pass encoding is available for DivX (libavc), but only two pass is available for XviD.

[yonidass]

That's what I was afraid of. It's not really worth it for me to do 2 or 3 pass encoding since I have a G3 and single pass takes long enough. I was hoping that tweaking the settings in some way might do it.

Thanks for the info anyway.

[thoughton]

Also double check your bitrate calculations. Even with single pass, encoding to 580MB when you were aiming for 700 is pretty inaccurate. Maybe you got the movie duration wrong or something.

[qshartle]

im back everyone(sorta) I can only give info because I dont have a mac in japan.....yet. What I used to do was encode the audio and video separately. Such as encode the audio first. Usually at 128 or 162, then see what that size was. Then set the auto bitrate by the time and 700-size of audio. That gave me much better results. Then mux it together with AVItool. I would try this way with a movie you want good quality on(such as Kill Bill or The Matrix).



Q

PS: I am starting to have engrish!

[Mr.Ash]

What about the Qmin and Qmax settings? Qmin should always be 2. The higher you set the Qmax, the bigger the compression but quality gets lost. The compression can be high even when you chose Qmax 3! This depends of how much movement the movie contains. A movie with low motion can be compressed very efficient without big qualityloss.

[Wibbler]

Long before getting ffmpegX or even a Mac, I have been using the mplayer/mencoder programs to create the 700MB avi's, and even now that I have the Mac I find that my old command-line method is still easier and more reliable.

I actually use the utilities as a 4 pass encode, with the first pass to dump the DVD stream to the hard disk and encode from there, that way I'm not hogging the DVD drive for the rest of the process, and also can encode more that one DVD stream at a time.

The second pass is to scan through the DVD stream and produce an Audio only output which the bitrate calculation is based on for the remaining two passes.

The third pass is to produce a Video only output along with a log file of video settings for each frame in the DVD.

The final pass is to integrate the Audio and Video data and fin-tune each frames video to give a clean output file.

The whole process does take time but would usually finish if left running overnight (867MHz G4 laptop) but on my 1.4GHz Celeron Linux system the whole process takes around 5 hours for all 4 passes.

The laptop DVD drive is one stumbling block as the Linux box can dump most DVD streams in around 12 mins.

If you want better Video quality then use MP3 Audio rather than AC3 as AC3 can take up more than twice the space of MP3, even though the encoding time for AC3 is a lot lower.

W.I.Bler