What is the point of Nth pass?

unimatrixzer0 · 11th March 2004, 20:10

For a while now I've been doing First Pass, then Nth (+2) Pass, so a total of 3 Passes. The only reason I've been doing 3 is because I was under the impression that it produces a better looking video w/ Divx 5.x.

My question is do the extra passes deal with compression and trying to produce a more compressed file, or does it effect the quality of the video. Because if the 3rd pass doesn't make the video look any better and just helps make the output file small then I'd rather not have to waste that time on a 3rd pass.

Thanks.

Soulhunter · 11th March 2004, 20:59

Simple answer... Test it out !!!

Source:

Chaser Trailer - MPEG1 (CG) / 1:19 min / 25fps / 384x288

MultiPass 250 kbps / No Psy. / Bidi Enc. / Standard

Pass1:
Time: 03:02 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.24

Pass2:
Time: 02:52 min. / Size: 16.564.224 Bytes / Avg. PSNR: 40.46

Pass3:
Time: 02:51 min. / Size: 16.564.224 Bytes / Avg. PSNR: 40.55

MultiPass 250 kbps / Fast Psy. / Bidi Enc. / Standard

Pass1:
Time: 03:02 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.24

Pass2:
Time: 03:28 min. / Size: 16.566.272 Bytes / Avg. PSNR: 40.31

Pass3:
Time: 03:26 min. / Size: 16.562.176 Bytes / Avg. PSNR: 40.22

MultiPass 250 kbps / Fast Psy. / Bidi Enc. / Slowest

Pass1:
Time: 15:22 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.54

Pass2:
Time: 15:29 min. / Size: 16.562.176 Bytes / Avg. PSNR: 42.02

Pass3:
Time: 15:43 min. / Size: 16.560.128 Bytes / Avg. PSNR: 41.17

MultiPass 250 kbps / Slow Psy. / Bidi Enc. / Standard

Pass1:
Time: 03:20 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.24

Pass2:
Time: 04:18 min. / Size: 16.568.320 Bytes / Avg. PSNR: 40.19

Pass3:
Time: 04:28 min. / Size: 16.560.128 Bytes / Avg. PSNR: 40.10

MultiPass 250 kbps / Slow Psy. / Bidi Enc. / Slowest

Pass1:
Time: 15:32 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.53

Pass2:
Time: 15:50 min. / Size: 16.562.176 Bytes / Avg. PSNR: 41.93

Pass3:
Time: 16:51 min. / Size: 16.560.128 Bytes / Avg. PSNR: 41.09

But the results could change with other sources...

Bye

bond · 11th March 2004, 21:08

3rd pass makes sense quality-wise in divx5 (surely not speed-wise

)

but a good codec should be able to do the same thing with two passes (like xvid

)

Soulhunter · 11th March 2004, 21:17

Ok, my first sample could be misleading...

Here is another one !!!

Source:

The Matrix - Lobby Shootout / 3:07 min. @ 25fps / 1024x576 pix. (Lanczos)

MultiPass @2500 kbps / No B-Frames / No QP / No PVE / Standard
2nd Pass: Size: 58.718.208 Bytes / Avg. PSNR: 43.28 / Time: About 04:02 min. (2600XP)
3rd Pass: Size: 58.677.248 Bytes / Avg. PSNR: 43.29 / Time: About 04:11 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / No QP / Fast PVE / Standard
2nd Pass: Size: 58.673.152 Bytes / Avg. PSNR: 43.03 / Time: About 04:57 min. (2600XP)
3rd Pass: Size: 58.681.344 Bytes / Avg. PSNR: 43.04 / Time: About 05:02 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / No QP / Slow PVE / Standard
2nd Pass: Size: 58.742.784 Bytes / Avg. PSNR: 42.74 / Time: About 07:19 min. (2600XP)
3rd Pass: Size: 58.667.008 Bytes / Avg. PSNR: 42.74 / Time: About 07:26 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / QP / No PVE / Standard
2nd Pass: Size: 58.679.296 Bytes / Avg. PSNR: 42.76 / Time: About 14:13 min. (2600XP)
3rd Pass: Size: 58.703.872 Bytes / Avg. PSNR: 42.76 / Time: About 14:17 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / QP / Fast PVE / Standard
2nd Pass: Size: 58.726.400 Bytes / Avg. PSNR: 42.39 / Time: About 14:49 min. (2600XP)
3rd Pass: Size: 58.679.296 Bytes / Avg. PSNR: 42.39 / Time: About 14:52 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / QP / Slow PVE / Standard
2nd Pass: Size: 58.728.448 Bytes / Avg. PSNR: 42.12 / Time: About 16:27 min. (2600XP)
3rd Pass: Size: 58.710.016 Bytes / Avg. PSNR: 42.12 / Time: About 16:28 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / No QP / No PVE / Slowest
2nd Pass: Size: 58.673.152 Bytes / Avg. PSNR: 43.60 / Time: About 28:43 min. (2600XP)
3rd Pass: Size: 58.697.728 Bytes / Avg. PSNR: 43.61 / Time: About 28:45 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / No QP / Fast PVE / Slowest
2nd Pass: Size: 58.744.832 Bytes / Avg. PSNR: 43.15 / Time: About 28:48 min. (2600XP)
3rd Pass: Size: 58.679.296 Bytes / Avg. PSNR: 43.17 / Time: About 28:49 min. (2600XP)

MultiPass @2500 kbps / No B-Frames / No QP / Slow PVE / Slowest
2nd Pass: Size: 58.730.496 Bytes / Avg. PSNR: 42.98 / Time: About 30:59 min. (2600XP)
3rd Pass: Size: 58.740.736 Bytes / Avg. PSNR: 42.99 / Time: About 31:00 min. (2600XP)

Bye

DigitAl56K · 12th March 2004, 01:54

The benefit of Multipass is not so much that you expect better PSNR, but that you expect a greater quality consistency throughout the entire file. I.e. you do not watch it and think "Wow you can see a lot of blocks in this scene, but the last scene looked really good..." - which can happen in 1-Pass mode.

You should read through the Multipass section of the DivX Users Guide, it explains some of the principles behind multipass and the benefits you will typically see from it.

Sharktooth · 12th March 2004, 12:05

3rd pass is also useful to reallocate bitrate manually thru the EKG.
As D56K said it smoothes out the blockiness and weird stuff that may happen in a 1-2 pass encoding.
3rd pass is "optional" and should be used only when needed (if you care about the encoding time).

11th March 2004, 20:10	#1 \| Link
unimatrixzer0 Registered User Join Date: Jan 2003 Posts: 61	What is the point of Nth pass? For a while now I've been doing First Pass, then Nth (+2) Pass, so a total of 3 Passes. The only reason I've been doing 3 is because I was under the impression that it produces a better looking video w/ Divx 5.x. My question is do the extra passes deal with compression and trying to produce a more compressed file, or does it effect the quality of the video. Because if the 3rd pass doesn't make the video look any better and just helps make the output file small then I'd rather not have to waste that time on a 3rd pass. Thanks.

11th March 2004, 21:08	#3 \| Link
bond Registered User Join Date: Nov 2001 Posts: 9,770	3rd pass makes sense quality-wise in divx5 (surely not speed-wise ) but a good codec should be able to do the same thing with two passes (like xvid ) __________________ Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau) I know, that I know nothing (Socrates) MPEG-4 ASP FAQ \| AVC/H.264 FAQ \| AAC FAQ \| MP4 FAQ \| MP4Menu stores DVD Menus in MP4 (guide) Ogg Theora \| Ogg Vorbis use WM9 today and get Micro$oft controlling the A/V market tomorrow for free

12th March 2004, 01:54	#5 \| Link
DigitAl56K Registered User Join Date: Nov 2002 Location: San Diego, CA Posts: 936	The benefit of Multipass is not so much that you expect better PSNR, but that you expect a greater quality consistency throughout the entire file. I.e. you do not watch it and think "Wow you can see a lot of blocks in this scene, but the last scene looked really good..." - which can happen in 1-Pass mode. You should read through the Multipass section of the DivX Users Guide, it explains some of the principles behind multipass and the benefits you will typically see from it. __________________ DivX Plus Web Player 2.0 (MKV & AVI) (Embed generator) DivX H.264 Decoder with DXVA support Developer portal

12th March 2004, 12:05	#6 \| Link
Sharktooth Mr. Sandman Join Date: Sep 2003 Location: Haddonfield, IL Posts: 11,768	3rd pass is also useful to reallocate bitrate manually thru the EKG. As D56K said it smoothes out the blockiness and weird stuff that may happen in a 1-2 pass encoding. 3rd pass is "optional" and should be used only when needed (if you care about the encoding time). __________________ MPEG-4 ASP Custom Matrices: EQM V1(old), EQM AutoGK Sharpmatrix (aka EQM V2), EQM V3HR (updated 01/10/2004), EQM V3LR, EQM V3ULR (updated 04/02/2005), EQM V3UHR (updated 17/12/2004) and EQM V3EHR (updated 05/10/2004) Info about my ASP matrices. MPEG-4 AVC Custom Matrices: EQM AVC-HR Info about my AVC matrices My x264 builds. Mooo!!!

11th March 2004, 20:59	#2 \| Link
Soulhunter Confused Join Date: Apr 2003 Location: Euroland Posts: 2,820	Simple answer... Test it out !!! Source: Chaser Trailer - MPEG1 (CG) / 1:19 min / 25fps / 384x288 MultiPass 250 kbps / No Psy. / Bidi Enc. / Standard Pass1: Time: 03:02 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.24 Pass2: Time: 02:52 min. / Size: 16.564.224 Bytes / Avg. PSNR: 40.46 Pass3: Time: 02:51 min. / Size: 16.564.224 Bytes / Avg. PSNR: 40.55 MultiPass 250 kbps / Fast Psy. / Bidi Enc. / Standard Pass1: Time: 03:02 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.24 Pass2: Time: 03:28 min. / Size: 16.566.272 Bytes / Avg. PSNR: 40.31 Pass3: Time: 03:26 min. / Size: 16.562.176 Bytes / Avg. PSNR: 40.22 MultiPass 250 kbps / Fast Psy. / Bidi Enc. / Slowest Pass1: Time: 15:22 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.54 Pass2: Time: 15:29 min. / Size: 16.562.176 Bytes / Avg. PSNR: 42.02 Pass3: Time: 15:43 min. / Size: 16.560.128 Bytes / Avg. PSNR: 41.17 MultiPass 250 kbps / Slow Psy. / Bidi Enc. / Standard Pass1: Time: 03:20 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.24 Pass2: Time: 04:18 min. / Size: 16.568.320 Bytes / Avg. PSNR: 40.19 Pass3: Time: 04:28 min. / Size: 16.560.128 Bytes / Avg. PSNR: 40.10 MultiPass 250 kbps / Slow Psy. / Bidi Enc. / Slowest Pass1: Time: 15:32 min. / Size: 14.090.240 Bytes / Avg. PSNR: 40.53 Pass2: Time: 15:50 min. / Size: 16.562.176 Bytes / Avg. PSNR: 41.93 Pass3: Time: 16:51 min. / Size: 16.560.128 Bytes / Avg. PSNR: 41.09 But the results could change with other sources... Bye

11th March 2004, 21:17	#4 \| Link
Soulhunter Confused Join Date: Apr 2003 Location: Euroland Posts: 2,820	Ok, my first sample could be misleading... Here is another one !!! Source: The Matrix - Lobby Shootout / 3:07 min. @ 25fps / 1024x576 pix. (Lanczos) MultiPass @2500 kbps / No B-Frames / No QP / No PVE / Standard 2nd Pass: Size: 58.718.208 Bytes / Avg. PSNR: 43.28 / Time: About 04:02 min. (2600XP) 3rd Pass: Size: 58.677.248 Bytes / Avg. PSNR: 43.29 / Time: About 04:11 min. (2600XP) MultiPass @2500 kbps / No B-Frames / No QP / Fast PVE / Standard 2nd Pass: Size: 58.673.152 Bytes / Avg. PSNR: 43.03 / Time: About 04:57 min. (2600XP) 3rd Pass: Size: 58.681.344 Bytes / Avg. PSNR: 43.04 / Time: About 05:02 min. (2600XP) MultiPass @2500 kbps / No B-Frames / No QP / Slow PVE / Standard 2nd Pass: Size: 58.742.784 Bytes / Avg. PSNR: 42.74 / Time: About 07:19 min. (2600XP) 3rd Pass: Size: 58.667.008 Bytes / Avg. PSNR: 42.74 / Time: About 07:26 min. (2600XP) MultiPass @2500 kbps / No B-Frames / QP / No PVE / Standard 2nd Pass: Size: 58.679.296 Bytes / Avg. PSNR: 42.76 / Time: About 14:13 min. (2600XP) 3rd Pass: Size: 58.703.872 Bytes / Avg. PSNR: 42.76 / Time: About 14:17 min. (2600XP) MultiPass @2500 kbps / No B-Frames / QP / Fast PVE / Standard 2nd Pass: Size: 58.726.400 Bytes / Avg. PSNR: 42.39 / Time: About 14:49 min. (2600XP) 3rd Pass: Size: 58.679.296 Bytes / Avg. PSNR: 42.39 / Time: About 14:52 min. (2600XP) MultiPass @2500 kbps / No B-Frames / QP / Slow PVE / Standard 2nd Pass: Size: 58.728.448 Bytes / Avg. PSNR: 42.12 / Time: About 16:27 min. (2600XP) 3rd Pass: Size: 58.710.016 Bytes / Avg. PSNR: 42.12 / Time: About 16:28 min. (2600XP) MultiPass @2500 kbps / No B-Frames / No QP / No PVE / Slowest 2nd Pass: Size: 58.673.152 Bytes / Avg. PSNR: 43.60 / Time: About 28:43 min. (2600XP) 3rd Pass: Size: 58.697.728 Bytes / Avg. PSNR: 43.61 / Time: About 28:45 min. (2600XP) MultiPass @2500 kbps / No B-Frames / No QP / Fast PVE / Slowest 2nd Pass: Size: 58.744.832 Bytes / Avg. PSNR: 43.15 / Time: About 28:48 min. (2600XP) 3rd Pass: Size: 58.679.296 Bytes / Avg. PSNR: 43.17 / Time: About 28:49 min. (2600XP) MultiPass @2500 kbps / No B-Frames / No QP / Slow PVE / Slowest 2nd Pass: Size: 58.730.496 Bytes / Avg. PSNR: 42.98 / Time: About 30:59 min. (2600XP) 3rd Pass: Size: 58.740.736 Bytes / Avg. PSNR: 42.99 / Time: About 31:00 min. (2600XP) Bye