diffrence between 1pass and 2 pass encodeing?

[sarmin]

hi i'm a noob but i think you already know.

is there a big diffrence in quality when making a 1pass encode compared to a 2pass encode?

cuz i though is there isn't a bigg diffrence then i can make 1 pass encodes and save 40min of encoding time. and when i say quality diffrence i mean when you are whatching a move in it's normal size not like making in 300% bigger just to see a diffrence. so my question is there a big diffrence? and how big is the diffrence?

[mats.hogberg]

IMO - There's a difference, but to me, rarely enough to justify twice the encoding time. But then again, so many factors are involved, it can't be answered with "Yes, 2-pass is twice as good" or anything like that. I think you'll have to try it yourself, and make up your own mind.

/Mats

[Nelson37]

If 40 minutes of encoding time is that important to you, then the improvement is probably not worth it to you.

As someone who used to do 4-pass re-encodes, IMO why not let the PC make the video as good-looking as possible while I am sleeping?

Unless you believe that someone else can tell you whether chocolate is better than pistachio, the only answer is try it for yourself and you decide.

[MOVIEGEEK]

The encoder makes a huge difference also(ie MainConcept vs. NeroVision).

[sarmin]

i'm useing virtualdub-mpeag2 and it convert files to xvid. so how big is the diffrence?

[lenti_75]

it is better

if you do 6000kbs or above, you won't "see" any difference on tv, 2 pass is still better, but your eye will never notice it.

now, there is CBR or VBR, constant bitrate and variable bitrate.....VBR is better again, especailly for fast moving action.

the best way (and my way), if you can wait, is VBR with 2 pass encoding. this way, the encoder alocates more bitrate for fast action when needed, and you get extra quality for 2 pass encoding, and I don't encode lower than 5000 no matter what, I better use 2 discs and 8000 bitrate than 4000 and 1 disc.

you still can do CBR with 1 pass, which is faster, if you encode above 6000 you won't see a difference on tv, but that is up to you.

[sarmin]

i wonder how cbr 1pass is compared to 2pass. i make 1 cd rips or less. so is the quality diffrence big?

[mats.hogberg]

CBR 2 pass is pointless. 2 pass is always VBR.

/Mats

[Nelson37]

The higher the target compression ratio, the greater the benefit to multi-pass encoding.

This is not a question that can be quantified, like "is 3 greater than 2?" Do it, View it, and YOU make the call.

If I were to tell you that pistachio is in fact better than chocolate, and I can prove it, would that make any sense to you?

[sarmin]

yes

[Nelson37]

OK then do multipass, it is ALWAYS worth the extra time and effort.

[lchiu7]

I was encoding some sports recorded off TV for a friend to be sent electronically so I was interested in the best compromise between quality and size. The video was captured off analogue cable using a WinTV card using IUVCR and mjpeg format.

He was going to watch on a PC so it had to be deinterlaced and I also applied some virtualdub filter to clean up the image a bit.

For 90 minutes of video, Athlon XP 2400+ (so modest machine) a one pass compress to xvid took 7 hours (maintaining same image size) with a final avi file of about 450MB! I thought about doing two pass and lowering the target bit rate so I could get a smaller file with the same quality but the thought of 14 hours just didn't appeal.

As a matter of interest I did notice if I dropped de-interlace (I was using the internal filter) times dropped to 3 hours! So maybe I should just not bother and let him de-interlace the video while he watches using a soft DVD player.

[guns1inger]

The other aspect that has not been addressed here is target size accuracy. I-pass VBR cannot guarantee the target size, whereas 2-pass VBR will give you the size you are after (assuming a good encoder, of course).