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Encoder Setting Tips

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List of settings

Video Scaling

Video scaling allows you to scale video input for lower bitrate streaming. Possible video scaling resolutions include: 320x180p, 480x270p 640x360p, 854x480p, 720x576p, 960x540p, 1280x720p, 1920x1080p, and 3840x2160p (VersaStreamer 4K and EdgeCaster only). 

The Passthrough option outputs the same resolution as the input.

Limit to 30 FPS

If Limit to 30 FPS is turned on, the input framerate will be cut in half. For example, if you have a 720p60 input with Limit to 30 FPS on, the encoded resolution will be 720p30. This is useful for low bitrate streaming.

If Limit to 30 FPS is turned off, the encoded framerate will be the same as the input.

Encoding Mode

Encoding Mode allows you to select the encoding bitrate mode for the MPEG-2 Transport Stream container.

  • For a constant video bitrate, select Constant Bitrate.
  • For a variable video bitrate, select Variable Bitrate.

Note: To achieve a Constant Bitrate stream (CBR) both the audio and video profiles must be set to Constant Bitrate encoding mode.

Keyframe Interval

Keyframe Interval controls the length of time between keyframes. It can be defined in seconds or in frames. For low bitrate streaming, choose a larger interval.

The keyframe interval is aligned with sub-GOPs, so it is possible the actual keyframe interval in the stream is slightly shorter than the configured interval.

Example:
Framerate = 60fps
Codec = H.264
Keyframe Interval = 1 second
Quality/Latency = Normal
GOP = IPBBPBB...PBB
Sub-GOP Size = 3 frames (PBB)
GOP Size = 58 frames instead of expected 60

Quality/Latency

Quality/Latency setting controls how many B-frames there are per sub-GOP for H.264 (AVC). Normal is the recommended value.

A B-frame is a tradeoff of quality vs. latency. B-frames offer better compression, so you'll get better quality video for your bandwidth. B-frames also add a frame of latency per-B-frame. 2 B-frames per sub-GOP = 2 frames of added latency. Having no B-frames can allow you to decrease latency by a small amount.

For H.264 (AVC), when Quality/Latency are set to:

  • High = 3 B-frames per sub-GOP
  • Normal = 2 B-frames per sub-GOP
  • Low = 1 B-frame per sub-GOP
  • Lowest = No B-frames 

When encoding 4K, B-frames are disabled for H.265 (HEVC).

Otherwise, for H.265 (HEVC), when Quality/Latency are set to:

  • High = 3-layer hierarchical B-frames, 9 B-frames per sub-GOP* 
  • Normal = 1-layer hierarchical B-frames, 2 B-frames per sub-GOP (recommended)
  • Low = 1-layer hierarchical B-frames, 1 B-frame per sub-GOP
  • Lowest = No B-frames

*3-layer hierarchical B-frames have compatibility issues with some players, Normal is recommended in these cases. Normal, Low and Lowest have no known compatibility issues. 

Video Encoding

Video Encoding allows you to set video encoding to H.264 or H.265. Note that H.265 is not supported for RTMP (limited by RTMP protocol, not Videon devices).

Video Encoding also allows you to set the target bitrate for your stream. Choose a lower bitrate for lower bandwidth streaming and a higher bitrate for higher quality streaming.

H.264 Profile

H.264 Profile allows you to set the profile to High (VersaStreamer/VersaStreamer SDI only), Main, or Baseline (VersaStreamer/VersaStreamer SDI only). As long as it is supported by the decoder, it is recommended to use either High or Main profile. This allows for lower bandwidth and higher quality video.  

 

H.265 Profile

When encoding H.265 the profile must be set at Main.

 

Audio Encoding

Audio Encoding allows you to set the audio encoding codec and bitrate value to use for the encoded audio.

Videon devices support MPEG-4 AAC LC at 64 kbps, 96 kbps, 128 kbps, 192 kbps, 256 kbps, 320 kbps, 384 kbps, and 512 kbps.

Note: For a Constant Bitrate (CBR stream) both the audio and video encoding profiles must be set to CBR. If one is set to CBR and the other to Variable bitrate (VBR) then the outputted stream will be VBR. 

 

 

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