DM8148 MPEG4 encoder problem

Hello,

What you are observing when the bitrate is low?

BR
Margarita

Hello,

We observed that all the length of the output bitstream are zero if we set the target bitrate is 99k, encode 4CIF@2fps.
or when target bitrate is 32k, encode CIF@15fps, the same problem happened in mpeg4 encoder.

if we increase the target bitrate upto 96kbps, then encode CIF@15fps is no problem.

thanks,

Hello,

Is there any feedback ?

thanks,

Hi Dwayne,

I tried to reproduce the issue for CIF with attached configuration but I am seeing always non-zero bytesGenrated for every frame.

Please share your configuration.

6567.encoder.cfg

Hi Ramprasad,

Thanks for your response !
Could you try again with setting below variable to 1 and using CBR rate control mode(rcAlg = 2)?

allowFrameSkip
XDAS_Int32 Input Controls the frame skip feature based on the bit
consumption.
 2 – Enabling early frame skip
 1 – Enabling late frame skip
 0 – Disabling frame skip

We found that if this variable is set to 0, encoder is working normally.
but if this variable is 0, output bitrate is always higher than our expected.

here is our configuration for your information.
if more information is needed for analysis, please let me know, thank you very much.
format = IVIDEO_MPEG4SP;
profile = 3;
dataLayout = IVIDEO_FIELD_SEPARATED;
fieldMergeEncodeEnable = FALSE;
maxBitRate = 10000000;
encodingPreset = XDM_USER_DEFINED
rateControlPreset = 1;
enableHighSpeed = 0;
enableAnalyticinfo = 0;
enableWaterMarking = 0;
numTemporalLayer = 1;
intraFrameInterval = 0;
interFrameInterval = 0;

targetBitRate = 32000;
mvAccuracy = 1;
rcAlg = 2;
qpMin = 2;
qpMax = 28;
qpInit = -1;
vbrDuration = 8;
vbrSensitivity = 0;

thanks,

Hi Dwayne,
With your settings, I am seeing only 6 bytes are generated from each frame from second frame onwards.
All frames are encoded as SKIP frames.

I had set useShortVideoHeader to 0 and observed 6 bytes in each frame.
With useShortVideoHeader=1, I am seeing bytesGenerated = 0 for all frames.

Hi Ramprasad,

Thanks for your promptly response !
After my trying, the result is the same as yours.
I have taken a look at UG and found that

useShortVideoHeader
XDAS_UInt32 Input Controls the encoding format.
1 - H.263
0 - MPEG4
Default value is 0.
If useShortVideoHeader is 1, MPEG4
Encoder automatically sets the
minBlockSizeP to
IMPEG4_BLOCKSIZE_16x16 . But can
have H.241 (resyncIntervalInbits) feature
with outputMode set to SLICE_MODE. See
more details about this in Appendix A.

But for our requirement, encoding H.263 header format is needed (useShortVideoHeader = 1),
Do you have any other ideas about this problem?

Big thanks for your supporting !

Hello,

any ideas to about the problems?

thanks,

Hi Dwayne,
Encoder's rateControl algorithm may have been implemented to behave this way at low bitrate.
Only encoder/RateControl algorithm team can answer if this is expected behaviour.

Hi Ramprasad,

Thanks for your replay.
codec forum is read-only right now, is there any other way to raise the question to codec team ?

thanks,

Hi,

any feedback ?

thanks,

Hi Johnson,

Could you please send the first frame size with your configuration?

Regards,
Karthick

If the first frame consumes more than your target bitrate then this behavior is expected. So please send the size of your first frame with your configuration where all the successive frames sizes are zero.

Also please let us know your codec library version that you are using.