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Transcoder Settings

The following tables list the Kraken Transcoder settings.

Basic Parameters

Transcoder Setting


Transcoder Name

Enter a unique name for the transcoder. This name will be selectable from the list of Transcoders when you define a stream.


(Optional, to enable hardware acceleration on qualified hardware, if detected) Select the encoding type, either: 

  • Software (default, Kraken legacy): CPU-based encoding
  • Hardware (QSV): Video encoding will be hardware accelerated using the Intel Quick Sync Video capabilities of the processor.
  • Hardware (<name #n>): Enables encode processing from the Kraken transcoder to be handled by NVIDIA GPUs. Assumes Kraken is running as a VM in an ESXi 6.5+ environment. Offloads the transcoding processing to the NVIDIA GPUs so that the server CPU remains free to be utilized by other applications. See Kraken OVA Deployment Guide.


    Capabilities of the particular NVIDIA card dynamically affect available (basic) parameters, for example, NVIDIA does not support Intra-refresh or B-frames.


Select the video compression standard for the outbound stream, either:

  • H.264 (AVC) (default)
  • H.265 (HEVC)
  • MPEG-4 (Part 2)
  • MPEG-2: The stream will be transcoded to MPEG-2 Video (ISO/IEC 13818-2) and MPEG-1 or MPEG-2 audio with closed captioning pass-through. This allows Kraken to inter-operate with legacy systems.

Codec Profile

(Format must be MPEG-2 or MPEG-4) Select the video profile for the encoder:

  • Auto: Defaults to Main profile.
  • Simple: Specifies that the output encoded video will adhere to the ISO/IEC 13818-2 / MPEG-2 Simple Profile.
  • Main: Specifies that the output encoded video will adhere to the ISO/IEC 13818-2 / MPEG-2 Main Profile.

Video Bitrate

Type in the Video Bitrate in kbps for the outbound stream, for example, 1024. Range = 1..100000


Select the resolution for the outbound stream:

  • Auto (Detect Continuously) (default)
  • Auto (Detect on Stream Start)
  • Custom: Type in a horizontal and vertical (W x H) resolution, for example, 1280x720. 


To maintain the resolution of the outbound stream that was detected at stream start (even if the input resolution changes), select “Auto (Detect on Stream Start)”.

720x576 or lower is considered SD resolution.


With NVIDIA encoders, Kraken provides validation of custom resolutions and notification when a stream exceeds supported resolutions.

KLV Metadata

Check this checkbox to enable KLV metadata passthrough.


Disabled if KLV isn’t licensed.

Frame Rate

Select the coded picture frame rate per second (fps):

  • Auto (Detect Continuously) (default)
  • Auto (Detect on Stream Start)
  • Select a frame rate from the list: 60..1


In previous releases, selecting “Auto” caused the frame rate of the outbound stream to be what was detected at stream start. The legacy “Auto” setting has been renamed “Auto (Detect on Stream Start)” since it does an early detection of the input frame rate and uses that as the fixed output frame rate for the transcoder.

The new default “Auto (Detect Continuously)” is an additional encoding/transcoding mode where the output Frame Rate follows the source frame rate. This mode monitors the incoming frame rate and if it can detect a steady frame rate that differs from the one it is currently using, it resets the video encoder and configures it accordingly.


Select the number of B-frames and B reference frames per P-Frames to allow in the output stream:

  • Auto (default): The Kraken software decides how many B-Frames and B reference frames to allow
  • IP: I and P frames only (lowest delay; lowest quality)
  • IBP: I, B and P frames
  • IBBP: I, BB (two B-frames and B reference frames in sequence) and P frames (higher delay; higher quality)
  • IBBBP: I, BBB (three B-frames and B reference frames in sequence) and P frames (highest delay; highest quality)


B-Frames improve the quality by increasing the efficiency of the encoding, thus allowing higher quality at the same bitrate. But B-Frames increase the encoder processing overhead, e.g., higher CPU utilization of the encoder.

GOP Size

Type in the GOP (Group of Pictures) Size for the outbound stream, for example, 30.

Range = 0..1000


You may choose to adjust the GOP to get different video quality on the outbound stream or to make the stream compatible with a different system than the original stream was intended for.


Increasing the GOP size can increase the time required for a player to tune into the stream. Reasonable GOP sizes tend to range from half the frame rate to up to 5 times the frame rate. A GOP size equal to the output frame rate is a good rule of thumb.

Intra Refresh

Check this checkbox to enable Intra Refresh for X.264 and X.265. This is an advanced feature that puts the encoder into a mode where it does not generate I-Frames. Instead the individual macro blocks are refreshed and over time all of the picture is refreshed.

This eliminates I-Frame bitrate spikes and smooths the bitrate over the GOP interval. The GOP parameter is still used as a basis for the refresh interval.


Not all decoders may support this feature so it can be enabled/disabled as desired.

Audio Parameters

Transcoder Setting



Check this checkbox to enable audio on the outbound stream.


Kraken will automatically insert a silent audio stream into the output when the input source has no audio (see “Silent Audio Insertion” under Recommended Start Settings for Advanced Shaping Settings).


When audio is removed on the outbound stream, the PID for the audio track is removed, as is the reference to it in the PMT.

Audio Codec

Select the audio compression algorithm:

  • Auto: Defaults to MPEG1 Layer II
  • MPEG1 Layer II: Encodes audio using the ISO/IEC 11172-3 / MPEG-1 Layer II algorithm.
  • MPEG2 AAC ADTS: Encodes audio using the ISO/IEC 13818-7 / MPEG-2 AAC-LC algorithm with an ADTS header.
Audio BitrateType in the Audio Bitrate in kbps for the outbound stream, for example, 128. Range = 14..576 Kbps

Advanced Parameters

Transcoder Setting


Performance Control System(Video Format must be HEVC) Check this checkbox to enable the Performance Control System, an HEVC encoder feature that dynamically monitors the runtime performance of the encoder and adjusts the video encoder quality based on the instantaneous performance of the encoder. The goal is to provide optimal quality of the video encoder based on the performance of the system. It is particularly useful on small form factor (i.e., lower power) systems such as Kraken CR.

Transport Stream Shaping

Check this checkbox to enable Shaping on the outbound stream.

Checking this checkbox also displays advanced settings (see Advanced Shaping Settings).


Traffic Shaping is used on some networks to smooth the traffic and respect the absolute upper limit configured. When Shaping is enabled, you can set the Maximum Bitrate for the Transcoder Stream (see Transport Stream Bitrate in Advanced Shaping Settings).


When Shaping is enabled, the Video Bitrate becomes the ceiling video bitrate target. When Shaping is disabled, this parameter represents the average video bitrate.

Output Pacing

(Kraken appliances only. Transport Stream Shaping must be disabled.) Check this checkbox to enable Output Pacing on the outbound stream.


Output Pacing is used to make the traffic more or less smooth on the network, to allow the stream traffic to leave the Kraken in a more even manner.

When pacing is enabled, you can set the Output Pacing Buffering Interval (see below).

Output Pacing Buffering Interval

(Output Pacing must be enabled) This Buffering Interval defines the depth of the Output Pacing in milliseconds (ranging from 0 to 1000ms). It is used to define the latency and smoothness added by the output pacing.

You can either type in a value between 0 and 1000 ms. in the text box, or move the slider to the desired value.


The higher the buffer is set, the more smooth the traffic is on the network. However, the optimal buffer setting will depend on the “spikiness” of the source stream.

Interleave Adjustment

(Optional) Type in the number of milliseconds to delay audio before multiplexing (“muxing”).

Range = -5000, 5000ms

  • 0 (Default Value).  No interleaving adjustment.
  • > 0 specifies the number of milliseconds to delay audio before muxing.
  • < -1 Number of milliseconds to delay video before muxing.


Interleave adjustment is actually a muxer interleave adjustment of the packets without touching timestamps and does not affect AV sync.


The latency within the transcoder pipeline is higher for the video than the audio, so users typically want to delay the audio so that the video comes out of the muxer before the corresponding audio. By default, the transcoder attempts to adjust the interleaving to some appropriate value. This control allows you to override that when desired.

PCR Delay

(Optional) Type in the number of milliseconds to delay the  PCR  (Program Clock Reference) behind the STC (System Time Clock). The  PCR  is the clock reference that is contained in the  MPEG transport stream . It is used to signal to downstream decoders a consistent clock by which to time other media essences (such as audio, video, closed captioning, and metadata).


This setting may be used to fine-tune stream timing for sensitive downstream decoder systems on streams with high relative delay between audio and video data within an MPEG2 Transport Stream.

Range =   0, 10000ms

  • 500 (Default Value) 
  • Target Ranges: 

    • IPTV: 2,000 <=> 5,000

    • ISR: 300 <=> 1,000

  • Increasing the value may incur additional latency at the player (i.e., larger buffers at the player):

    • Greater than 5000 may cause unintended issues with remote players.

    • Lower than 300 may introduce unstable audio playback issues.

Jitter Buffer

(Optional) Type in the Jitter Buffer for the inbound source/stream. A jitter buffer may be applied to video streams coming in at irregular intervals to help output the video in a steady stream (default = 250 ms).

Range = 0, 5000ms


Transcoding latency will be affected proportionately.

KLV Decimation

Transcoder Setting



(KLV Metadata pass-through must be enabled) Select "By Factor" to frame-decimate ingested KLV messages to reduce the bandwidth used by the metadata service.

  • None
  • By Factor: 1/2..1/60


1/2 means divide the amount by half, etc.

Factor ("By Factor" must be selected) Select the decimation factor.

UAS KLV Tag Filtering

Transcoder Setting


UAS KLV Tag Filtering

(KLV Metadata pass-through must be enabled) Specifies a list of tag numbers/labels from the UAS Datalink Local Set that are allowed to be streamed. Tags not included in this list will be discarded. Select either:

  • None
  • Minimum Set: the set of metadata objects as define in MISB 0902.
  • All: the set of metadata objects as defined in MISB 0601.
UAS KLV Security Tag Filtering

Specifies a list of tag numbers/labels from the Security Local Data set inside the UAS that are allowed to be streamed. Tags not included will be discarded. Select either:

  • None
  • Minimum Set: the set of metadata objects as define in MISB 0902.
  • All: the set of metadata objects as defined in MISB 0102.


#48 must be included under UAS KLV Tag Filtering.


An asterisk (*) next to a field indicates that it is required.

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