UMC Mpeg-4 encoder bitrate question

UMC Mpeg-4 encoder bitrate question

Hi, I am using UMC Mpeg-4 VideoEncoder to encode uncompressed video into MP4 Part2 vidoes. I set the video output bitrate to 1.5Mbps. And most time it works fine. But when the input video is all noise, the output video data frame is huge. It is way over 1.5M per second. It overflows our output buffer (we do have a limited size of output buffer). Is there a way to control that, for example, set the MAX bitrate instead of average bitrate?


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Hello Wes,

I've made a request of the engineers for clarification.

In the meantime, have you tried the RateControl member? The UMC manual has the following description:



[in] The rate control algorithm.
0 - ConstQuality with quantIVOP, quantPVOP, quantBVOP
1 - Frame Level AVBR;
2 - Macroblock Level CBR


Hi Paul,

Thank you for the response. But we tried all three numbers, and still not working the way we hope it runs.


Okay. I spoke with engineering this morning, will post their feedback when it becomes available.


Sorry for the delayed reply, here is engineering's response to your question regarding control of the bitrate:

...there is no effective way to control the output stream bitrate. All parameters either operate [on the] average bitrate or dont relate directly to bitrate.

There might be two ways to overcome this situation

- application-wide algorithmic way. When the application sees MPEG-4 data not fitting into output buffer, this data must be dropped, or frame rate must be lowered down, or something else with quantization values.

- to increase the encoder output buffer. Ultimately, it must be capable to store uncompressed amount of video data. It hard to say without knowing of application details.

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