[Mp4-tech] [H.264] strange rates

[Stéphane PECHARD]

> Maybe a simplistic selection of BasicUnit=TotalMBsInPicture would be a
> good start.

Thanx for this, I have "more logical" QP now. But the bitrate is still way
too much in the first GOP. Here is the result of a sequence coded at
4Mbps, the first frame (an IDR) is more than 4Mb in itself !
Is RC that bad in the codec ?
Following I put the Rate control part of the codec configuration file.
Do you see where it can come from ?
Best Regards,
Stéphane
-------------------------------------------------------------------------------
  Frame  Bit/pic    QP   SnrY    SnrU    SnrV    Time(ms) MET(ms) Frm/Fld Ref
-------------------------------------------------------------------------------
0000(NVB)     184
0000(IDR) 4646640   24  38.746  41.417  42.346    262750       0    FRM    1
0002(P)   2589144   24  36.641  40.568  41.922    406813  133127    FLD    1
0001(B)   2315984   23  37.184  40.953  41.997    678656  360966    FRM    0
0004(P)   2420272   24  36.678  40.594  42.005    502485  230955    FLD    1
0003(B)   1302240   25  35.453  40.652  41.858    646719  361664    FRM    0
0006(P)   1725304   26  35.331  40.291  41.642    475844  231024    FLD    1
0005(B)    730480   27  34.186  40.523  41.599    614188  359320    FRM    0
0008(P)   1151880   28  33.994  39.910  41.242    458672  234749    FLD    1
0007(B)    477096   29  33.395  40.107  41.233    594360  359971    FRM    0
0010(P)    854824   30  32.636  39.578  41.016    443391  232447    FLD    1
0009(B)    369560   31  32.291  39.709  41.065    582438  360746    FRM    0
0012(I)   3365712   26  37.142  40.990  42.101    231515       0    FRM    1
0011(B)    386008   31  32.319  39.203  40.984    584781  361285    FLD    0
0014(P)   1643480   26  35.257  39.673  41.389    478859  231344    FLD    1
0013(B)    336888   32  31.423  39.605  40.850    580032  361981    FLD    0
0016(P)   1800504   26  35.246  39.889  41.379    481860  232067    FLD    1
0015(B)    536848   30  32.165  38.836  40.722    596828  362036    FRM    0
0018(P)   1309904   28  33.833  39.232  40.895    463250  230504    FLD    1
0017(B)    550616   29  32.993  39.028  40.982    598781  361426    FRM    0
0020(P)    873656   30  32.530  38.846  40.851    444516  231419    FLD    1
0019(B)    441440   31  31.653  39.010  40.790    586875  360287    FRM    0
0022(P)    744536   32  30.882  38.077  40.198    434516  228781    FLD    1
0021(B)    282840   33  30.171  38.084  40.243    573640  360156    FRM    0
0024(I)   3035440   28  35.436  39.488  41.187    220172       0    FRM    1
0023(B)    265912   33  30.757  38.439  40.490    572141  361016    FRM    0
0026(P)   1250688   28  33.807  38.976  40.859    461765  231844    FLD    1
0025(B)    164880   34  30.652  38.570  40.644    563922  359951    FLD    0
########################################################################################
#Rate control
########################################################################################
RateControlEnable    =      1   # 0 Disable, 1 Enable
Bitrate              =  4000000   # Bitrate(bps)
InitialQP            =     24   # Initial Quantization Parameter for the
first I frame
                                # InitialQp depends on two values: Bits
Per Picture,
                                # and the GOP length
BasicUnit            =     8160   # Number of MBs in the basic unit
                                # should be a fractor of the total number
                                # of MBs in a frame
ChannelType          =      0   # type of channel( 1=time varying channel;
0=Constant channel)
--
~ stéphane péchard
~ phd student | irccyn-ivc | france
~ http://www.irccyn.ec-nantes.fr/~pechard
~~~~~~ pgp : hkp://subkeys.pgp.net ~~~~~~