Capturing To AVI vs MPEG1 vs MPEG2

[kinneera]

Show me a uncompressed AVI and Ill show you a Divx of equal quality, did you know they use compression on DVD's ?

Come on now, this really is badly misinformed. Do you have even the faintest understanding of lossy compression and data entropy? No Divx will ever have a comparable data fidelity to uncompressed AVI, especially not a realtime capture. Even if you think you can't tell a quality difference, there is - a HUGE one. Video with a data rate of maybe 4.5MB/min cannot even hope to compare to uncompressed video at ~1.2GB/min, it's just basic math. And your MPEG encoder will see something very different when it tries to encode from your Divx file, namely extremely large quantities of digital artifacts and only a tiny fraction of the original video data. Similar reasoning explains why studio masters produce better VCDs than even DVD rips. And why most videophiles would find the idea of transcoding Divx to SVCD laughable.

Divx is intended as an end-target format, not an intermediary capture format. If you don't intend to post-encode to MPEG1 or MPEG2, then by all means capture to Divx if you have a reason to and a sufficiently fast computer. But don't tell people to use it as a capture codec for VCD/SVCD/DVD encodes - then we'll just have people coming back complaining about how bad the final product turned out because they don't understand GIGO.

[KingJohn]

Ok so it matters to the person that there is a difference even if it cannot be seen ?

The point is, that some of the older computers with slow hard drives will loose more frames than they will capture, how good is the capture then ? compared to capturing with Divx on the same machine, where the processor might cope when the hard drive transfer fails.

I tell people to try capturing to Divx as a means of at leased achieving something, rather than get frustrated with the results they have.

I don't go around telling people DivX is the only way, and I don't expect someone to denounce as useless, when it produces good results.

Further more quite a lot of people don't want to produce VCD's and so want a means of storing large amounts of AVI on regular CDR, those people would benefit enormously by compression.

My statement points out that a divX file will "look" as good as an uncompressed file.

I guess you have not seen many good DivX movies, I suggest you have a look at some of them before you pass judgment, rather than point out technical merits of the two.

[kinneera]

I don't necessarily dislike Divx in and of itself. What I do disagree with is the following:

1. Use Divx as a capture format if you can't do uncompressed AVI without frame drops. No - if you can't handle uncompressed AVI, use a lossless AVI codec like Huffyuv. If you still can't handle it, try a high bitrate I-frame only MPEG capture. If you still can't handle it, you probably need to reconsider your hardware, as any computer with a hard drive so slow that it can't handle those formats probably doesn't have a processor anywhere near fast enough to produce a realtime Divx capture of anywhere near acceptable quality.

2. I'm not making a VCD anyway. If you're not capturing to make a VCD or SVCD, then its worth considering realtime Divx capture. You will absolutely need a fast computer (at least 1 Ghz) to achieve decent quality in realtime, in which case hard drive related frame drops probably aren't an issue anyway. Incidentally, the author of the thread clearly stated his target format is VCD/SVCD anyway, so I stand by my very emphatic recommendation that he not use Divx as the intermediary format. What you're essentially saying is throw away 80% of the info, then double the 20% that's left to get the target format. Not a winning solution.

3. Well, my Divx looks as good as uncompressed AVI. Making a truly good Divx requires non-realtime, 2-pass encoding with lots of parameters considered and tweaked. It sure as heck isn't going to happen in realtime, especially if the source is something like a noisy tape. Plus, like I said before, if it is being used as an intermediary compression, what your eyes see is very different than what an MPEG encoder sees. It is most assuredly not as good as uncompressed AVI. Divx encoding introduces more artifacts than any other method (lossy compression, simple math), its just much better at hiding them from our really quite imperfect sensory organ. Those artifacts will be of catastrophic significance to an MPEG encoder, though.

4. It sounds like you haven't seen a good Divx. I have seen what I would call decent/good Divx rips, but I'm sure they were produced very caringly under non-realtime conditions, like I addressed above. Even then, not even the good ones I've seen hold a candle to a well-produced SVCD, and are no-contest losers to DVD, much less uncompressed AVI.

Divx is good for what it does. I have no problem with that. But if you can't capture anything without resorting to Divx, then you probably need to reevaluate your hardware before delving into the video hobby. And realtime-captured Divx will sure as hell never look as good as uncompressed AVI, even if - as a format - Divx can be utilized to produce video that creates that illusion under different conditions.

[tjdmobile]

I use DIVx for all my captures destined for VCD. I set mine to 1-pass slowest, 6000. maximum 15 frames between I-Frames. Sure, it's not 100% identical to Huffy, but works great for most situations.

This said, I don't ever capture sports or fast action movies. For these, you really should cap uncompressed to get the best quality possible.

IMHO, that is!

TJD

[KingJohn]

Well its obvious that a better PC is needed, but not all people can afford to upgrade all the time, what works well on more powerful machines wont work very well on slower machines, so I suggest that those slower machines can handle DivX better than they would handle un-compressed AVI's. Quite a lot of the older machines have fast processors but are bottle necked with other poor components.

I have seen transfer rates on hard drives in kb/sec instead of Mb/sec, yes they also have on board 1Mb graphics cards.But usually have a good processor.

[drak23]

djnibler:

I also suggest you exchange the card. I was trying the same things you are with the USB version of the card you have. I ran into a lot of problems (partly learning curve) and eventually decided that it just wasn't going to capture at the resolution and quality I wanted. I upgraded to the 7500 and am much happier with the capture capability. I use MMC to capture w/ huffuv to an AVI file, then I have high-quality source (relatively speaking) to work with. You need a lot of hard disk space for this though (1 hour = about 10GB).

FYI I'm using a PIII 700MHz machine outfitted with a 100GB hard drive.

Drak

[Nelson37]

DJnibbler -
There is a tweak to the install file described here somewhere for setting hardware detection to 0, this seems to solve the no TV app problem, although for the AIW cards, don't know about the TV wonder.
ATI doesn't support MMC 7.5 or 7.6 for my AIW 128 but both worked just fine.
The TV wonder is a different beast and seems to have several issues - exchange it if you can.
On Divx - if it works and looks good for you, do it. Mathematical proofs are meaningless if they disagree with what your eyes tell you, though you might want to get a few friends (or better yet, enemies) to confirm that visual opinion.