Limitations of AMD Xilinx acceleration with Wowza Streaming Engine transcoding

The Wowza Streaming Engine 4.8.22 and AMD Xilinx Alveo U30 integrated flow has several limitations with U30 usage. These will be addressed in the upcoming release versions of Wowza Streaming Engine.

The main features of an Alveo U30-based flow (decoding, scaling, encoding) are hardware accelerated, enabling high-density real-time transcoding for live streaming.

Note: If the integrated flow is run on a free-trial mode, the scaling is performed on the CPU. For more trial information, see Wowza Streaming Engine Free Trial.

Each AMD Xilinx Alveo U30 card has two devices. When a system is fully loaded or the number of simultaneously processed input streams is more than five per device, you may experience system instability. This may require you to restart Wowza Streaming Engine.


The following sections include limitations of using an Alveo U30 card in the Wowza Streaming Engine 4.8.22 and AMD Xilinx Alveo U30 integrated flow:

General limitations

  • During transcoding jobs, you may observe system instability, or some output streams may not be generated. To fix this issue and restart the transcoding jobs, restart Wowza Streaming Engine.

U30 decoder limitations in Wowza Streaming Engine

  • U30 does not support interlaced video streams. You can use the Wowza SW decoder for de-interlacing.
  • YUV 420 planar is not supported.
  • SEI message is not retrievable. For example, closed captions.

U30 scaler limitations in Wowza Streaming Engine

  • The input and output aspect ratio must be the same. For example, changing from 16:9 to 4:3 does not work.
  • Resolutions from 128x128 to 3840x2160 in multiples of four are supported. 
  • Using a stretch fit mode when configuring a transcoding template is recommended.
  • ABR ladder for 4Kp60 input streams is not supported (example: 4Kp60 -> 4Kp60, 1080p60, 720p60). However, ABR ladders for 4Kp30 input streams are supported (example: 4Kp30 -> 4Kp30, 1080p30, 720p30, 480p30).
  • Frame rate reduction is supported. The limitation is that the first output needs to match the incoming frame rate (example: 1080p60 -> 1080p60, 720p30, 540p30).
  • Input and output overlay is not supported.
  • YUV 420 planar is not supported.
  • Crop, rectangle, and letterboxing (black filling) are not supported.

U30 encoder limitations in Wowza Streaming Engine

  • SEI message metadata is not insertable. For example, closed captions.
  • YUV 420 planar is not supported.
  • U30 lookahead is not supported.
  • Keyframe insertion capability is not supported.
  • Profile propagation to the output stream is not supported. A high profile is always written to the output stream.