Enabling Constant Bitrate Encoding (CBR) in Wowza Transcoder

The Wowza Trasncoder uses the MainConcept SDK. To check the encoder capabilities enable the logVideoEncodingParameters option in <Encode><Properties> the section of the transcoder template (WowzaStreamingEngine/transcoder/templates):

<Property>
    <Name>logVideoEncodingParameters</Name>
    <Value>true</Value>
    <Type>Boolean</Type>
</Property>

Restart the application to apply the new changes. The supported bitrate modes are listed in the Wowza access log:

# long: bit_rate_mode: bit rate stuff: 0=H264_CBR, 1=H264_CQT, 2=H264_VBR or 3=H264_TQM

To enable constant bitrate (CBR) add the following parameters to the <Encode><Video><Parameters> section of the template:

  • mainconcept.bit_rate_mode (0=H264_CBR)
  • mainconcept.bit_rate
  • mainconcept.bit_rate_buffer_size (VBV)

Example for H264_CBR 1000 kbps, sizes are in bits:

<Parameter>
    <Name>mainconcept.bit_rate_mode</Name>
    <Value>0</Value>
    <Type>Long</Type>
</Parameter>
<Parameter>
    <Name>mainconcept.bit_rate</Name>
    <Value>1000000</Value>
    <Type>Long</Type>
</Parameter>
<Parameter>
    <Name>mainconcept.bit_rate_buffer_size</Name>
    <Value>40000</Value>
    <Type>Long</Type>
</Parameter>

Restart the application once again to apply the parameters. The chosen values should show up in the Wowza access log. Don’t forget to disable the parameter logging once everything is in place.

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