HCEnc overcompensating on bitrate?

[NerdWithNoLife]

I've had this issue on several encodes. HCEnc keeps saying "adjusting average bitrate," at a percentage that gets higher and higher as the encode goes on. On my latest, by the end it reported bitrate adjustments of 55%! The input AVS takes a 720p file, IVTC's and resizes to 720x480. Are these adjustments because I specify a max GOP of 14 with no B frames? Does anyone else do that?

I figured you'd want the log file so here's the whole whopping thing:
| HCenc - MPEG2 encoder - rel. 0.22.0.0 |


MPEG profile@level: MP@ML

input: c:\tv\fringe dvd\fringe.avs

output: C:\TV\Fringe DVD\fringeDVD.m2v



--------------------

| encoder settings |

--------------------



profile: BEST

frames: 0 136750

framerate: 23.976

aspect ratio: 16:9

bitrate Kb/s: 6600

max. bitrate Kb/s: 6600

pulldown: no

closed gops: no

VBV check: yes

scene change det.: yes

interlaced: no, BFF

goplen,B-pic: 14 0

dc_precision: 10

scan method: zigzag

bias: 0

chapter frames: 9

time code: 0 0 0 0

CPU: SSE3

priority: idle

SMP active: yes

matrix: MPEG

luminance gain: no



------------------

| source stats |

------------------



nr. of frames in source: 136751

width*height: 720x480

fps: 23.976

nr. of frames to encode: 136751

frames to encode: 0 - 136750



---------------------

| encoding - pass 1 |

---------------------



pass 1 encoding time: 1:27:59 (5278.80 s)

fps: 25.9



--------------------------------

| encoding - intermediate pass |

--------------------------------



bitrate set to: 6589 kb/s

est. outfile length: 4587895 kB

intermediate encoding time: 42.3 s



---------------------

| encoding - pass 2 |

---------------------



*** INFO, adjusting average bitrate: -0.36 %

*** INFO, adjusting average bitrate: -0.74 %

*** INFO, adjusting average bitrate: -0.89 %

*** INFO, adjusting average bitrate: -1.09 %

*** INFO, adjusting average bitrate: -1.70 %

*** INFO, adjusting average bitrate: -2.18 %

*** INFO, adjusting average bitrate: -2.52 %

*** INFO, adjusting average bitrate: -3.09 %

*** INFO, adjusting average bitrate: -3.50 %

*** INFO, adjusting average bitrate: -3.91 %

*** INFO, adjusting average bitrate: -4.39 %

*** INFO, adjusting average bitrate: -4.94 %

*** INFO, adjusting average bitrate: -5.41 %

*** INFO, adjusting average bitrate: -5.73 %

*** INFO, adjusting average bitrate: -6.22 %

*** INFO, adjusting average bitrate: -6.49 %

*** INFO, adjusting average bitrate: -6.91 %

*** INFO, adjusting average bitrate: -7.49 %

*** INFO, adjusting average bitrate: -8.06 %

*** INFO, adjusting average bitrate: -8.63 %

*** INFO, adjusting average bitrate: -9.24 %

*** INFO, adjusting average bitrate: -9.87 %

*** INFO, adjusting average bitrate: -10.67 %

*** INFO, adjusting average bitrate: -11.28 %

*** INFO, adjusting average bitrate: -11.80 %

*** INFO, adjusting average bitrate: -12.47 %

*** INFO, adjusting average bitrate: -13.16 %

*** INFO, adjusting average bitrate: -13.74 %

*** INFO, adjusting average bitrate: -14.30 %

*** INFO, adjusting average bitrate: -14.64 %

*** INFO, adjusting average bitrate: -14.80 %

*** INFO, adjusting average bitrate: -15.41 %

*** INFO, adjusting average bitrate: -16.10 %

*** INFO, adjusting average bitrate: -16.68 %

*** INFO, adjusting average bitrate: -17.29 %

*** INFO, adjusting average bitrate: -18.01 %

*** INFO, adjusting average bitrate: -18.49 %

*** INFO, adjusting average bitrate: -18.68 %

*** INFO, adjusting average bitrate: -19.23 %

*** INFO, adjusting average bitrate: -19.91 %

*** INFO, adjusting average bitrate: -20.78 %

*** INFO, adjusting average bitrate: -21.58 %

*** INFO, adjusting average bitrate: -22.51 %

*** INFO, adjusting average bitrate: -23.38 %

*** INFO, adjusting average bitrate: -24.05 %

*** INFO, adjusting average bitrate: -24.96 %

*** INFO, adjusting average bitrate: -25.62 %

*** INFO, adjusting average bitrate: -26.37 %

*** INFO, adjusting average bitrate: -26.80 %

*** INFO, adjusting average bitrate: -27.16 %

*** INFO, adjusting average bitrate: -27.75 %

*** INFO, adjusting average bitrate: -28.46 %

*** INFO, adjusting average bitrate: -28.98 %

*** INFO, adjusting average bitrate: -29.61 %

*** INFO, adjusting average bitrate: -30.48 %

*** INFO, adjusting average bitrate: -30.97 %

*** INFO, adjusting average bitrate: -31.39 %

*** INFO, adjusting average bitrate: -32.14 %

*** INFO, adjusting average bitrate: -33.10 %

*** INFO, adjusting average bitrate: -34.01 %

*** INFO, adjusting average bitrate: -34.60 %

*** INFO, adjusting average bitrate: -35.05 %

*** INFO, adjusting average bitrate: -35.67 %

*** INFO, adjusting average bitrate: -36.67 %

*** INFO, adjusting average bitrate: -37.11 %

*** INFO, adjusting average bitrate: -37.88 %

*** INFO, adjusting average bitrate: -38.79 %

*** INFO, adjusting average bitrate: -39.51 %

*** INFO, adjusting average bitrate: -40.65 %

*** INFO, adjusting average bitrate: -41.72 %

*** INFO, adjusting average bitrate: -42.45 %

*** INFO, adjusting average bitrate: -43.21 %

*** INFO, adjusting average bitrate: -44.31 %

*** INFO, adjusting average bitrate: -45.23 %

*** INFO, adjusting average bitrate: -46.16 %

*** INFO, adjusting average bitrate: -46.82 %

*** INFO, adjusting average bitrate: -47.22 %

*** INFO, adjusting average bitrate: -47.93 %

*** INFO, adjusting average bitrate: -48.58 %

*** INFO, adjusting average bitrate: -49.62 %

*** INFO, adjusting average bitrate: -50.83 %

*** INFO, adjusting average bitrate: -51.75 %

*** INFO, adjusting average bitrate: -53.19 %

*** INFO, adjusting average bitrate: -54.37 %

*** INFO, adjusting average bitrate: -55.01 %

pass 2 encoding time: 2:13:39 (8019.12 s)

fps: 17.1



------------------

| encoding stats |

------------------





intra matrix used

8 16 19 22 26 27 29 34

16 16 22 24 27 29 34 37

19 22 26 27 29 34 34 38

22 22 26 27 29 34 37 40

22 26 27 29 32 35 40 48

26 27 29 32 35 40 48 58

26 27 29 34 38 46 56 69

27 29 35 38 46 56 69 83



non-intra matrix used

16 17 18 19 20 21 22 23

17 18 19 20 21 22 23 24

18 19 20 21 22 23 24 25

19 20 21 22 23 24 26 27

20 21 22 23 25 26 27 28

21 22 23 24 26 27 28 30

22 23 24 26 27 28 30 31

23 24 25 27 28 30 31 33



nr. of gops: 10823

nr. of frames: 136751

nr. of I-frames: 10823

nr. of P-frames: 125928

nr. of B-frames: 0

average bitrate: 4234

minimum bitrate: 123

maximum bitrate: 6599



bytes in bitstream: 3019697148

bits in bitstream: 24157577184



average Quantizer: 3.351



total CPU time: 5:44:02 (20641.75 s)

total elapsed time: 3:42:21 (13341.08 s)

[45tripp]

bitrate Kb/s: 6600

max. bitrate Kb/s: 6600



.....

[blutach]

What 45tripp is trying to say in a very shorthand manner is to increase your max bitrate. 8500 should give the encoder room to move on high BR scenes.

Also, read this post (http://forum.doom9.org/showthread.php?p=1002957#post1002957) and the one following.

Regards

[NerdWithNoLife]

When I set the max bitrate to 8000, it caused a buffer underflow according to Muxman. I've had spikes up near 11000 at a max bitrate of 8000! The audio is 448k BTW.

In this particular video, bitrate viewer reports a peak of 7308 and an average of 3967. I suppose I'll have to settle for b-frames if the encoder can't handle it.

[hank315]

A buffer underflow reported by Muxman means a VBV issue.
Reading your log it shows you're using HC022, this version sometimes had VBV problems, this was fixed in HC023, please update...

With 448k audio, a maxbitrate of 8500 should be OK.

Is there a specific reason you don't want to use B-frames?

[45tripp]

What 45tripp is trying to say

"Try not. Do, or do not."

Know thy audience
:devil:

[NerdWithNoLife]

Excellent - it's great to see the VBV issue addressed in the new version.

Regarding b-frames, when I first began the quest to learn more about compression, I associated them with low bitrate video. The way I saw it, I could go with a low bitrate and use b-frames to salvage a little quality, or skip b-frames all together and use a higher bitrate for higher quality. B-frames are sort of a yoyo between reference frames that could be 2 or more frames apart, whereas p-frames just work from the frame immediately before, right? But perhaps b-frames are nothing to fear - and judging by my bitrate issue it's not working to do without them.

You sure know more about this than I do, Hank.:o

[blutach]

They are certainly nothing to fear.

Regards