More Video Creation hacks

I believe that I've blogged before about my video creation on FreeBSD. Here's some interesting tips for DIVX players that I've found.

First, to recap: I tape a lot of hockey games with my DV camera. I use
fwcontrol -R name.dv -M dv
to read in the tapes. I then use the kino port to do some editing and convert the .dv files into mpeg 2 files for the DVDs of the games I make. I convert the mpeg2 files to dvds using dvdauthor. When I want to be fancy, I use dvdstyler to create themes for the DVDs.

Recently, I had my DVD player of many years die on me. It refused to play disks. So I went out gone one that would play DivX disks, as well as normal DVDs. This one also has a USB port on it. Through trial and error, I discovered that I could save myself a lot of disks by putting the videos I wanted to test on a flash drive.

DivX videos, for those that don't know, are basically MPEG-4 AVI encoded rather than MPEGE-2 encoded like DVD movies. While DVD movies can play as low as about 4 or 5kbps, they are generally encoded at more like 10kbps. At that rate, the average single layer disc can hold about 2 hours of video. DivX movies are encoded at more like 1-2kbps, so are about 3-6 times smaller than their DVD encoded counterparts. Of course, these are gross generalizations, but good enough for people to understand.

Now, my problem is that I have about 18 hours of hockey games that I'd like to distribute to the parents of the other players. For my son's benefit, I had made one DVD per game, but with 11 other parents, the thought of making 200 DVDs filled me with dread: it was too much time, too much hassle and it was starting to get expensive.

So, I started experimenting with DivX encoded videos. I tried to get ffmpeg working, but ran into a number of snags that I basically punted on. I had used mplayer for years to watch other videos and DVDs, so I thought about using mencoder. kino had a mode that would encode the DV movies to something else, so I played around with it. I created two test videos. One was at 854x480. This is what you get when you film in 16:9 aspect ratio with a DV camera that has a resolution of 720x480. Google for anamorphic for all the reasons for this, but they can be summarized as non-square pixels converted to square pixels. For the curious, I used:
mencoder sample.mpeg -cache 8192 -aspect 16:9 -vf harddup,pp=ci,scale=854:480 \
-ovc xvid -oac mp3lame -lameopts preset=192 -xvidencopts bitrate=2048 -ffourcc DX50 \
-o high.avi
to encode the DVD-quality images into divx. This encoding resulted in a factor of 3-4 saving in file sizes. This was fairly good, but didn't get my 40GB of mpeg's to fit on one DVD. In addition, the DVD player I bought didn't like this resolution at all. I figured other people's DVD players wouldn't like it either. Next, I tried a reduced resolution version. I used
mencoder - -demuxer rawdv -quiet -cache 8192 -aspect 16:9 -vf harddup,pp=ci,scale=426:240 \
-af-adv force=1 -srate 44100 -ovc xvid -oac mp3lame -lameopts preset=medium \
-xvidencopts fixed_quant=4 -ffourcc DX50 -o medium.avi
which resulted in a space savings more like 6-10, which puts the encoding project within striking distance of one DVD. It is well under the DL DVD range, and might be very close to the single layer limit of 4.7GB. We'll have to see how the encoding goes. It is moving about 4x faster than the previous encoding as well.

One of these days, I'll need to learn how to do the fancy two-pass encoding to ring every bit of quality I can out of my source material. But for now, I'm doing good to get things encoded. I also need to find some way to tame the insane complexity of this problem. The above commands were basically minor tweaks to ones I found in kino's scripts to encode the video.

As for the DivX disk, I just copied the files over, and they played in alphabetical order. No way I could see to create a menu. No way to encode them in the .divx format that has menus and such in it, since I couldn't find the equivalent to dvdauthor for divx movies (please leave comments if you know of one for FreeBSD/Linux). For the hockey games for the parents, this is likely good enough. For other things, I'd like to do better...

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