Higher-than-Expected Bitrate in VBR Encoding with Zeroed vbvBufferSize and vbvInitialDelay

AI & Data Science Computer Vision & Image Processing
1

Dear NVIDIA Support Team,

I am writing to seek assistance regarding an issue we’ve encountered with our video encoding process using NVIDIA’s encoding technologies. Despite configuring our encoder to use Variable Bitrate (VBR) settings, the actual bitrate exceeds our expectations. Additionally, our configuration sets both vbvBufferSize and vbvInitialDelay parameters to zero.

Issue Details:

  • Expected Behavior: Achieve target bitrate as specified in VBR settings.
  • Observed Behavior: Actual bitrate is consistently higher than the target.
  • Configuration Parameters:
    • RateControlMode: VBR
    • vbvBufferSize: 0
    • vbvInitialDelay: 0
    • avgBitrate:25Mbps
    • maxBitrate:30Mbps
    • Actual Bitrate received: 49Mbps

System Information:

  • Operating System: Windows 11
  • NVIDIA GPU Model: NVIDIA RTX A2000 8GB Laptop GPU
  • Driver Version: 553.62
  • Encoding SDK Version: NVENCAPI_MAJOR_VERSION 11, NVENCAPI_MINOR_VERSION 1

Steps Taken:

  1. Configured the encoder with VBR settings and zeroed vbvBufferSize and vbvInitialDelay.
  2. Initiated the encoding process on various video samples.
  3. Monitored the output bitrates, noting consistent elevation above the target.

We would appreciate any guidance or recommendations you can provide to help us achieve the desired bitrate control in our encoding process.

Thank you for your attention to this matter.

Best regards,
Mehul