TV series DVDs to DivX at 'similar' quality

[broaddd]

I was interested in people's approaches to converting tv series DVDs to DivX while maintaining 'similar' quality. I've started to experiment with this task for the first time, and have been reading up on this site lately.

I'm motivated by thinking it would be nice to backup my DVDs of various TV series to half or less the number of DVD-Rs of DivX files at a quality such that I'd hardly notice the difference (and retain 5.1 sound where the source has it). I'll be playing them on the Xbox Media Centre player.

I've started with my PAL Star Trek Voyager discs. They're full-screen (720x576), 5.1 AC3 (384kbps). I've been using ffmpegX to take them to 640x480 with AC3 5.1 passthrough with reasonable results.

Should I compress the audio stream more? I know I should know this - but I should I deinterlace if I'm going to be playing back on TV? And I could do them at 768x576 I suppose, but I guess with 640x480 I'm at least getting the vertical resolution NTSC-people live with everyday

I know this task is nothing new, but look forward to any comments people feel like leaving

B

[spectroelectro]

Divx produces compression artifacts that can't be as easily eliminated by upping the bitrate as MPEG-2. Considering how cheap DVD-Rs are getting, it might not be a good idea to downconvert from DVD to DiVX. If you want identical video quality (as seen on an analog TV anyway) with half the number of discs, try downconverting from DVD MPEG-2 to SVCD MPEG-2 and author the SVCD video streams onto DVD. You can easily get 5 to 6 TV episodes in superb quality on one DVD using SVCD with out-of-spec bitrate -- 300 min, 2000 av 6000 max, then run ReJig to squish down each SVCD file to just under 700 megs.
Divx is okay but I'm not a big fan of the format. No matter how high you push the bitrate, the visible compression artifacts always seem to be there and it takes a L*O*T of virtualdub filtering to tone 'em down. Divx video artifacts are not subtle stuff. With Divx you get particularly bad video compression artifacts on near-monochromatic backgrounds -- it's really distracting to watching blocks of pixels keep shifting around like snakes on a barbecue in a background that's supposed to be one solid color. I find it distracts significantly from the video viewing experience on my TV series. Also, to get high-quality divx encoding you must start with the straight AVI (not from the already-comrpessed MPEG-2 stream on a DVD) and let even a very fast 2.8 Ghz p4 crank for a loooooooooooooooooooong time.

[broaddd]

Thanks,

I'm having a bit of difficulty understanding the practical effect of that, although I'm sure that's just me not understanding the difference between DVD and SVCD variations on MPEG-2.

A similar strategy seems to be joining the 5-6 episodes into one DVD image, and then re-encoding that at 352*576? But this no doubt demonstrates my ignorance

B

[xtreemkareem]

On the contrary broadd, you're taking the right path. By resizing to 352X576, you have resized to a 1/2 D1 resolution DVD, which is whithin the DVD standard for PAL. Authoring as SVCD-DVD would be pretty stupid if you ask me b/c:

1) Compatibilty - 1/2 D1 (aka D2, 352X576) DVD is 100% compatible. Only a number of players will play back SVCD-DVD (480X576)
2) At the same bitrates, D2 DVD resolution looks better than SVCD-DVD (more bits/pixel).

As for DivX, I'm pretty fond of it. The issues with DivX comes from DivX3, which causes so many crappy artifacts, especially with DVD ripss with too low a reolution. In which case you're better off vomiting on the TV set Newer versions of DivX (4.12 and 5.X) give really good results if done properly, and XviD can give pretty amazing results (with the ocasional bug). A faster machine helps, nut I think any computer you buy today, willencode DivX and amazing speeds. I'm not the hugest audiophile, so to save space, I always downsample audio tp 44 khz 112 kbps CBR MP3 (sounds just fine to me!). For video, try downsizing the reolsution a bit to get more data per pixel. Interlaced DivX content takes up twice as much space as progressive, but makes sure you have ALLl the data (usually no biggy for me). Hope this helps.

[Suntan]

All I can give you is what I use, not saying it is better than other approaches, but it looks great to me.

Koepi's Xvid rev 1.01 all default settings except set minimum I, B and P quantizers to 2 and use the "mpeg" quantizer matrix instead of the H263 matrix. Set the bitrate to 1500kbps

For audio convert to 2 channel Prologic II (surround2) Ogg Vorbis at quality 4 with Headac3he.

You get a 45 min episode at about 500 to 600 MB.

Some TV episode DVDs start out with less than the best quality (Alias Season 1 for example) so it is difficult to get great quality with them no matter what you choose.

-Suntan