D2sroba sizing?

[vifa]

I have been using d2sroba in transfering avi's to dvd. I have dome some reading in the forum but can't really find the answer. In this example:

- 2005-10-07 19:59:50
- Project dir: C:\Program Files\DVD2SVCD\Movie\
- Avisynth setup: LanczosResize
- Configured cond. filter: C:\Program Files\DVD2SVCD\Tylo\RoBaConditional.avs
- D2S ver. 1.2.2.3, CCE ver. 2.50.1.0
--------------------------------------------------------
- Movie length : 01:31:21 (131429 frames, 23.976 fps)
- D2S audio select : 192 + 0 kbps
- D2S video calc. : 6000 kbps, 1 CDs
- Select ranges : every 1200, select 12 frames
- Sample frames : 1320
--------------------------------------------------------
Calculations:
- 1 CD: video_br=6000 (6360) audio_br=192+0 video_sz=4111267517 fill=94.5% cbr=0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- Using num CDs : 1
- Target mpv br : 6000 (max 8000) kbps, size=4111267517 bytes
--------------------------------------------------------
Search for Q:
- Sample enc. Q=14 : 3129 kbps, err=-47.9%, size=2144616205, sample sz=21539336
- Sample enc. Q=6 : 4205 kbps, err=-29.9%, size=2881541795, sample sz=28940608
- Sample enc. Q=1 : 4445 kbps, err=-25.9%, size=3046065812, sample sz=30592996
--------------------------------------------------------
- Determined Q : 1 = Round(1 + (-25.9 - 1.4)/0.8)
--------------------------------------------------------
- 2005-10-07 20:01:34
- Start movie OPV encoding (Q 1)

--It estimates the target bitrate to be around 6mbps, so why then does it start the first iteration at 3.1 mbps? Why not 5.5?

--When the q gets to 1 does this mean that if the bitrate was increased to the max br to fill the disc, there would be no gain in quality?

--The reason I'm asking these questions is I have been getting some 3 gig movies that are over 110 minutes. I figure, any movie over 1 1/2" hours should be able to fill a 4.7g disc.

[ChickenMan]

What you have there is not unusual. A lot depends on the quality of the original AVI or VOB files. The initial Q value always starts at 14 for a 1hr 30min movie so I suspect its based on movie length. The bitrate of the first pass is calculated AFTER the pass and not before it. As it reaches Q = 1, then it achieves the max quality it can get for that particular file your encoding, and as the line says

- Sample enc. Q=1 : 4445 kbps, err=-25.9%, size=3046065812, sample sz=30592996

it is going to be 25.9% undersized. You will also notice that the next VBR pass achieves absoultely no gain in file size also (see the new ver of D2SRoBa to be released). You have reached the max quality achievable from that particular file and generally thay are undersized.

[vifa]

That is what I suspected but just wanted to make sure.

another question, Sometimes it goes to cbr mode, what variable causes it to enter this mode?

[ralphthedog]

d2sroba will go CBR when your target bitrate reaches the maximum bitrate you have set in DVD2SVCD (you have max 8000 in your log). It wouldn't be possible to do a VBR pass higher than max bitrate....