Unstable bitrate while changing bitrate dynamically

Devang panchal

Hello TI,

We are using DM8148 based custom board and using ezsdk_dm814x-evm_5_05_01_04 from software perspective.

In one of our application it is required to change bit-rate dynamically which we achieve successfully, but when we change bitrate dynamically, bit-rate is not stable. For example, we set initial target bitrate to 200 kbps and the actual corresponding bitrate is accurate (equal to 205-210 kbps). However, after switching target bitrate to 600 kbps the actual encoder output bit-rate is approximately 450 kbps.

we attached video sample here with the 600 kbps bitrate after 100 frames of video for your reference.

8156.7181.sample.rar

Please suggest.

Thanks,

Devang

over 11 years ago

0 Pavel Botev over 11 years ago

TI__Guru**** 170625 points

Devang,

Please refer to the below E2E thread:

http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/288641.aspx

For more h264 codec (and other multimedia codecs) related questions, you can ask in our Multimedia Software Codecs forum:

http://e2e.ti.com/support/embedded/multimedia_software_codecs/f/356.aspx

Regards,
Pavel

0 Krunal Patel_11 over 11 years ago in reply to Pavel Botev

Expert 2250 points

Hi Pavel,

http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/288641.aspx is the thread in which we have discussed about the insertion of I-Frame when we change the bit-rate.

In the present issue when I encode a file with bit-rate of say 200kbps then the encoded file do have a varying bit-rate from around 150kbps to 600kbps.

So can you please explain why this happens?

Can we control this varying bit-rate and make it stable to the specified bit-rate?

Thanks

Krunal

0 Pavel Botev over 11 years ago in reply to Krunal Patel_11

TI__Guru**** 170625 points

Krunal,

Please refer to the below guidelines, might be in help:

http://processors.wiki.ti.com/index.php/DM36x_H.264_encoder_FAQ#How_to_change_rate_control_mode.2C_frame_rate.2C_bitrate.2C_dynamically_in_H.264_encoder.3F

DM814x Silicon Errata, advisory 3.0.13

{EZSDK}/component-sources/omx_xx_xx_xx_xx/src/ti/omx/docs/H264_Encoder_HDVICP2_UserGuide.pdf

Regards,
Pavel

0 Santosh Kumar Kandagave over 11 years ago in reply to Pavel Botev

TI__Intellectual 840 points

Devang,

Could you please try updating HRDBufferSize and initialBufferLevel (these two rate control parameters are part of H264 encoder configurations) along with the new bitrate? Formulae to update these parameters are given in encoder's user guide.

Thanks.

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Unstable bitrate while changing bitrate dynamically