C66x H.264 HP encoder bitrate

Andrey Lisnevich

Hi,

We experience problems with configuring bitrate of H.264 HP encoder. Very often average bitrate goes higher than it is configured in encoder bitRate parameters.

As the example please review this docuements that contain encoder configuration, bitrate, sample input (MPEG-2 encoded), sample output (transcoded to H.264), etc:

https://drive.google.com/?tab=wo&authuser=0#folders/0B7aam1m6VieeRzh3am9lM1hxeEU

As you can see moving white text on black background causes 15 Mbit/s. It is almost 2x higher bitrate than configured 8 Mbit/s

Regards,

Andrey Lisnevich

over 12 years ago

0 Andrey Lisnevich over 12 years ago

Genius 3305 points

Also as I see old black and white movies cause higher bitrate than color ones. So problem in sample can be not in moving text, but in black and white palette of the frames. But it is only my guess.

Regards,

Andrey Lisnevich

0 Sudheesh over 12 years ago in reply to Andrey Lisnevich

Expert 1945 points

Hi Andrey,

HRD buffer size is given 5 times of target bit rate. This can cause big fluctuations in instantaneous bit rate.
Please check whether 16000000 or 20000000 as initial buffer level and HRD buffersize will be fine for your quality requirements.

Using CABAC and enableIntraPartition = 2 can improve further on bits consumption at the cost of increased cycles.

Please use for Level=40 as your input is 1080P.

Regards

Sudheesh

0 Andrey Lisnevich over 11 years ago in reply to Sudheesh

Genius 3305 points

Hi Sudheesh,

We applied your changes to configuration, you can see them in encoder_settings_updated file.

But bitrate still not good. Please check bitrate_updated.png file.

Regards,

Andrey Lisnevich

0 Sudheesh over 11 years ago in reply to Andrey Lisnevich

Expert 1945 points

Hi Andrey,

We further experimented with different config parameters and the attached params may be fine with your requirement.

We found significant drop in instantaneous bit rate in our test setup.

Major changes are using one B frame, QP changes and HRD buffer size changes, using CAVLC.

Thanks and regards

Sudheesh

0 Paula Carrillo over 11 years ago in reply to Sudheesh

TI__Mastermind 40580 points

Hi Andrey, please let us know if suggested changes worked for you

Thank you,

Paula

0 Andrey Lisnevich over 11 years ago in reply to Paula Carrillo

Genius 3305 points

Hi Paula,

Your configuration produces acceptable bitrate but I can't do 1080p30 in realtime on 4 cores using it. But after tweaking, using your hints, I was able to create configuration that runs on 4 cores.

Regards,

Andrey Lisnevich

0 Paula Carrillo over 11 years ago in reply to Andrey Lisnevich

TI__Mastermind 40580 points

Andrey, thanks for the confirmation.

Paula

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C66x H.264 HP encoder bitrate