Bitrate goes too high??

[Big_Jit]

I just got done making an SVCD of Antitrust, Quality is perfect. Here's the problem:

When I set the bitrate for the video I get a movie with a higher bitrate then I selected. All I've done so far is Disc 01 because I don't wanna have the movie across three discs. Current File size is: 904 MB

I set up TMPGEnc using these settings:

Video:
480 x 480 MPEG-2
4:3 aspect ratio
23.976fps (internally 29.97fps)
Constant Quality - Max: 2417 kbps
Min:876 kbps
Padding Enabled
Quality Slider @ 100%
vbv buffer size = 112
MP@ML
NTSC
3:2 Pulldown When playback
YUV Format 4:2:0
DC Component Precision 10bits
Motion Search Precision High Quality (Slow)
Video Source Type: Progressive
Field Order: Top Field First (Field A)
Source Aspect Ratio: 16:9 525 line (NTSC)
Video Arrange Method: Full Screen (keep aspect ratio)
Number of I picture in GOP: 1
Number of P picture in GOP: 5
Number of B picture in GOP: 2
Output interval of sequence header: 1 GOP
Max number of frames in a GOP: 18
Detect Scene Change: Enabled
Use Floating Point DCT (while using SSE, Always on): Enabled
No motion search for still picture part by half pixel: Enabled

Audio: Converted with 2lame using BeSweet
192kbps Stereo
48khz
Error protection: Enabled

Multiplexed as Super VideoCD using BBMPEG
_______________________________________

Bitrate Viewer Gives me the following output

Peak bitrate: 3168 <-- Way too High
Average bitrate: 2547 <-- " "
Minimum Bitrate: 1033 <-- " "

Num. of picture read: 75638
Stream type: MPEG-2 MP@ML VBR
Resolution: 480*480
Aspect ratio: 4:3 Generic
Framerate: 29.97
Nom. bitrate: 2417200 Bit/Sec
VBV buffer size: 56
Constrained param. flag: No
Chroma format: 4:2:0
DCT precision: 10
Pic. structure: Frame
Field topfirst: Yes
DCT type: Frame
Quantscale: Nonlinear
Scan type: ZigZag
Frame type: Progressive

Why does this happen and how do I fix It?

[sterno]

tmpgenc CQ mode doesn't do a very good job of honoring the maximum bitrate setting. If you want to try to keep your maximum in the right range for SVCD you should probably set your maximum down to around 2000k, or maybe down to 1800k. Also, when you have quality set to 100% you'll probably find that the average bitrate is pretty close to the maximum you set.

[sterno]

Oh, and just for the record, if you want your MPEG file to be a particular size you should use 2-pass VBR. If you don't mind doubling your encoding time you can exactly fill a CD.

[Big_Jit]

Thanks for the reply!

I'll keep that in mind when I do Future Encodes...

[DJRumpy]

I'm more curious about the audio. It should have been 44.1Khz, not 48Khz. As far as the max bitrate is concerned, I've heard it said that spikes above the max bitrate are not uncommon, and most players will handle them without a problem. If your really concerned, you can always use CBR, and remove any chance of variation.

If you standalone player supports it, make a small test using rewritable media to see if your player has a problem.

[Big_Jit]

I use 48khz because my player supports it so I see no use in converting to 44.1khz.

The problem isn't with the playability of the disc. It plays PERFECT Picture is PERFECT the problem was that I wanted to spread the movie across 2 discs and as it turns out it'll be going across 3 anyway. But next time I'll probably go with either the CBR or 2-pass routine even though I think CQ gives GREAT results in quality.

Thank's for your input!...

[BJ_M]

i see even huge spikes on CBR with TMPGEnc ...

also you have CQ set at 100% which will cause even larger spikes .. CQ at 100 is treated as CBR more or less.

81 - 84 seems resonable and works well ..

but as others mentioned VBR also is a possability ..

[DJRumpy]

I'm sold on VBR. I've been downloading so many movies lately, that that extra disk saved is becommnig substantial.

[Kevin Henry]

Yeah, TMP & CBR is a bit of a joke I've had a CBR of 2.8 and seen it spike every few seconds above 2x the 'constant' bitrate setting!

CCE solved that problem in hurry - much better. Pity it's a pain in the ass to use ...