mpeg2 vs. Divx

[grigory]

Well, obviously, I am a "newbie". I am just starting to capture video from VCR (I am not doing DVD ripping yet), and I want to preserve high quality (as high as possible on a VHS), because I have some priceless (at least for classical musicians, like myself) videos that are never going to be re-released, and I want to preserve as much fast-motion and sound detail as possible.

I have read all the guides, but I am still not clear on a simple point - which codec would give me better quality, if quality is more important for me than filesize.

If, for example, I want to fit a 45min. video on a 700MB CD, which would give me a better quality: mpeg2 (SVCD), or Divx (4 or 5)?
Of course, I understand that the higher the bitrate, the higher the quality with any codec, but still...

I understand that DivX is a more advanced codec, but is it designed for better quality at lower bit-rates, to be more easily downloadable, or is it in general better for archiving then mpeg2 as well?

I would appreciate any input.
Thanks!

[LotionBoy]

If you really want the best quality go with uncompressed Avi or something like HUFF-YUV, which gives you uncompressed video. But you're going to get a huge file. MPEG2 is very unwieldy for CDs. Personally, I would never try and fit anything to do with MPEG2 onto a CD. There is just not enough room. If you really just want to put video on a CD and don't care about the size, use Divx4 or Xvid and do a constant Quant. encode at DRF 2. This will give you a large file, with very good quality.

LotionBoy

[grigory]

Thanks for the help!
I just wanted to clarify - I thought I would get better quality by using VBR, rather than CBR, isn't that true?

I re-read my last post and realized I wasn't making much sense - what I meant was that I would rather NOT fit the file on one CD, but get a better quality.

I guess my real question is: with an original VHS which is already pretty noisy, is it feasable to get 45min video on 1 CD withought noticable loss of quality. If yes, which would be the best codec (and settings) for the job, if not - then assuming I would rather go for more CD's then loose more quality, which bitrate should I choose to get good results.

I assume that with VHS quality being what it is, there is no point in trying to do nearly-lossless compression, since the original quality is already rather low. I understand that the whole idea of lossy compression is that what we see (or hear) from a recording is already not "perfect" quality, and so there is a certain threshold of how much information can be "lost" further without noticable difference. I guess what I would really like to know from people with experience, who have dealt with VHS capturing, is where that threshold is.

If you can make any sense of my mumbling, I would appreciate further advice! Thanks again!

[LotionBoy]

VBR gives better quality than CBR when you are dealing with a bounded file size (Take 30 minutes of video and fit it into 200MB). When you do not care about the file size, CBR will give you the best possible quality. It might be possible to get the same quality in a smaller file with VBR, but probably not without a lot of work (if you want there to be any real filesize difference). A constant Quant encode at DRF 2x should be more than enough to deal with VHS quality material. As to whether it will fit on a CD, I can't tell you. That's the problem with Constant Quant: it is is kinda hard to predict the file size. If I had to guess, I would say yes, but that would be a very uncertain yes. The only way to find out is to try.

LotionBoy

[grigory]

Thanks again!

Just to try your patience more, I am a bit confused on the following:
you say that it is harder to predict the filesize with CBR than with VBR. Shouldn't it be the opposite? I mean a Constant Bit Rate means that there is a constant number of bits per second, which means that to calculate the bitrate you would simply need to multiply the desired final filesize (in bytes) by 8 and divide by the number of seconds, isn't that correct? Or did I misunderstand what you said?

One more thing: what is in your experience a good-enough (for VHS) quality bit-rate (if filesize is less relevant than quality)? (if I get it right, besides the DRF I also have to set the bitrate as well)?

Thank you!

[LotionBoy]

Alrightie, the confusion is my fault because I was mixing terms around. CBR has a predictable file size. But unpredictable quality (ie, some frames looks fine at 800, some frames need less than 800, some need more). Constant Quant encoding is what you want, and that has an unpredictable file size, even though it is constant quantizer (because different frames will come out different sizes, even if they have the same DRF). So you do not need to set a bitrate, just a constant DRF level (and you can do this with any codec you want. I would recomend Divx4/5 or Xvid).

LotionBoy

[grigory]

Got it,Thanks!