Question regarding CQ and CBR encoding

[noaht1980]

I have converted like 4 DVD2SVCD now and i have always used a CQ template well with CQ i always have to guess on what CQ # to use so i am gonna do a DVD2SVCD today and i wanna try CBR

can someone tel me exactly how to encode using CBR i mean i need to know how to tell what bitrates to use so i can make sure the final SVCD i get from it is nice quality and so i can make sure to get exactly 2 800mb files and also do i need to download tepmplate for it?,

If anyone can shed some light on this for me i would appreciate it

[snowmoon]

CBR bitrate or VBR average bitrate =

((output file size in kbytes / #of seconds in video) * 8) - audiobitrate - overhead

overhead is about 20-50kbpx

So to put a 60 minute video on an 80 minute disk as SVCD...

output filessize = 800mb = 819200kb
lenght in seconds = 3600 seconds
audio bitrate = 160

819200 / 3600 * 8 - 160 - 30 = 1630kbps CBR or VBR average

[noaht1980]

Thanx for the info

I just have one question the DVD is 98 mins so what min and max bitrates should i use to get the SVCD on 2 discs?

also do you think the quality will be better this then CQ ?

[snowmoon]

No CQ will produce better quality.

VBR is only really acceptable when the bitrate is about 2300 or so.

[Vejita-sama]

CBR - constant bitrate. During a CBR encode you set a bitrate and that bitrate is used for the entire video. It's easy to predict file size of your encoded MPEG. bitrate x runtime = filesize (Aside - notice that the bitrate is the only thing that affects file size, not motion search, size of your source file, or resolution).

The problem is that CDRs only hold 800MB (which is pretty small). And people want to put as much video as possible, at as high a quaility as possible, on each disc. The higher the bitrate the higher the quaility. But if I raise the bitrate I increase the file size, and that means less video (runtime) per CDR.

But when you think about it, a lot of the video is just people standing around doing nothing. Those low motion scences don't really need a high bitrate. I only really need to high bitrate during fast/motion scences.

(multiple pass) VBR - variable bitrate. Enter VBR, for a VBR encode you set a min bitrate, a max bitrate, and an average bitrate. The encoder will then lower the bitrate in low motion scences (but not below the min) and raise it in high motion scences (but not above the max). But do so such that the average bitrate works out to what you entered.

This means you can still predict file size. ave bitrate x runtime.

The first pass is normally a CBR encode, and the 2nd alliquots(sp) out the bitrate. Most people find that you get the best results encoding with multipass VBR by setting:

max = standalone players max (normally 2520kbit/s or so)
min = 300 or 500 (ie. REALLY low, to let the encoder play)
ave = # from bitrate caculator for desired final size of encode

TMPGenc only allows for 2pass VBR, the motion search setting tells TMPGenc how 'hard' to look for high vs. low motion scences. CCE allows for 5 (or is it 9) but most agree that anything about 3 (or 4) is just a waste of time.

TMPGenc also has CQ_VBR (constant quaility _ VBR) encoding. This sometimes called 1pass VBR encoding. Basically the VBR encoding is done on the fly to maintain 'constant quaility.' The problem is you CAN NOT predict the final file size using CQ_VBR encoding (yeah you can quess, but it varies depending on the motion in your source video).

If you use the max bitrate, just use CBR, for less than max bitrate encode VBR might be an option. How much less than max? Opinions vary. For VCD/CVD/SVCD the max video bitrate is 2520kbit/s (for most standalones). I use CBR for encode > 2200 kbit/s and VBR is the bitrate gets below that. I try not to let the bitrate drop below 1000 kbit/s (this is from memory I've got a DVDR drive now )

[poopyhead]

No CQ will produce better quality.

VBR is only really acceptable when the bitrate is about 2300 or so.

isn't CQ also a form of VBR...as the encoder tries to maintain Constant Quality throughout the video, meaning some scenes will require more/less bitrate to be perceived as the same quality as other scenes.

multi-pass VBR is still pretty good if your avg. bitrate goes below 2 mbit/s, but i don't think much lower. as long as the max bitrate is set to the max of 2520 kbit/s, then hopefully....those action scenes won't look too nasty

personally, i stay around 2.2 mbit/s for avg....i prefer quality over # of CDs