Is There Much Difference Between Quantizer 1 And 2 In Divx?

[Anakin]

I been playing around recently and doing some tests and I am just wondering. What is the main advantage of using 1? I have used 2 for some time now but played around with 1. Except for the file size going WAY up, I can not see any improvement.

Just for my own needs, does anyone have any detail in what the actual difference is? Is 1 loseless and 2 just a bit compressed?

[Anakin]

Or even 3?

[PuzZLeR]

Q=1: Lossless in visual quality. But still not lossless. A good option if you're archiving big acquisition formats, such as DV-AVI, and want a smaller file size instead (but do your edits first before encoding).

Q=2: Like Q=1, but more toned down - a smaller file size for an acceptance of the fact that some more detail is indeed lost, which may be more noticeable in motion scenes. Still good quality retention.

Q=3: This is what you should be encoding to for good small file sizes with an acceptable quality loss. This should be for the viewing of most of your special stuff. It should not be an archival format, only a good viewing one.

Q=4: Like Q=3, but for your not-as-special stuff. Some more quality loss, but smaller file size. Again, not an archiving format, only a good viewing one.

Q>4: Although file size shrinks, the quality begins to noticeably suffer. I would avoid.

At the DivX forums, we recommend 3 and 4 for typical DivX stuff - the best compromise of good quality and smaller file sizes. 1 and 2 should only really be for archiving source.

I would say Q=2 is a "reduced Q=1" and Q=4 is a "reduced Q=3".

[Anakin]

That is great, thank you for that. Also, just looking at the other settings. Can you tell me anything about Masking and Shaping? Also, what is Enhance I Blocks?

[jagabo]

Can you tell me anything about Masking and Shaping?

http://labs.divx.com/node/90
Both of these reduce the quality of the output when using constant quality encoding.

Also, what is Enhance I Blocks?

Normally I and P frames are encoded at the same quality (same quantizer), B frames at lower quality (higher quantizer). Enhance I Blocks will encode I frames with a higher quality (lower quantizer) than P frames. At low quantizers (1-3) the difference won't be very noticeable. At lower qualities I find this causes strobing. The I frame is nice and sharp, the picture degrades as you get further and further into the GOP. The picture sharpens up again at the next I frame, then degrades again...

I would avoid all those settings with constant quality encoding. But why don't you just run some test encodes and see for yourself?

[Anakin]

Hmm, very interesting. I must admit I try and avoid filters all I can as I like to keep faithful to the original. I have decided to test encode The Dark Knight DVD at Q3 with no filters. I will let you know how it goes when it have finished.

Thanks for the replies, appreciate it.

[jagabo]

Don't encode an entire movie. Encode a short segment with different settings then compare the results.

[Anakin]

Am I allowed to post screenshots of commercial films here? I do own the original DVD by the way?

[poisondeathray]

You are allowed to post small sample as per fair use rules (at least in North America, not sure about England). But what matters is how it looks to YOU, not someone else.