Unlock official Dolby AC-4 and Atmos playback in your multimedia pipeline with the only certified, legal GStreamer plugin on the market. By integrating fluac4dec, you instantly gain full control over next-gen metadata, allowing you to automate dialogue enhancement and personalize audio experiences for your viewers. Bridge the gap between open-source flexibility and professional compliance to launch your certified broadcasting solutions ahead of the competition.
We provide the only Dolby-certified path to AC-4 within the GStreamer and FFmpeg ecosystems.
We enable high-performance software decoding on generic hardware, eliminating the need for expensive, specialized DSP chips.
We provide the only Dolby-certified path to AC-4 within the GStreamer and FFmpeg ecosystems.
We enable high-performance software decoding on generic hardware, eliminating the need for expensive, specialized DSP chips.
Decodes Dolby AC-4 bitstreams into high-quality, raw PCM audio. It supports multiple formats from standard stereo up to 5.1.4 immersive audio layouts.
Includes a built-in renderer component that downmixes or renders the decoded audio to specific target speaker configurations (e.g., 5.1, 2.0 LoRo).
The decoder is able to negotiate capabilities out of the box with downstream an upstream components. If a target speaker configurations is not selected by the user, it’s able to communicate with the audio sink and negotiate the number of output channels.
Dynamically extracts and exposes real-time stream metadata, such as average bitrate, frame rate, active language tags, and dialogue normalization (dialnorm). This metadata is accessible through readable GObject properties and downstream sticky events, making it ideal for professional broadcast monitoring workflows.
Provides granular control over the audio output by allowing users to adjust the Presentation (presentation-index) or the Dialogue Enhancement gain (de-gain).
Includes on-the-fly pipeline changes, ensuring correct and safe element reconfiguration and caps negotiation.
Includes a built-in renderer component that downmixes or renders the decoded audio to specific target speaker configurations (e.g., 5.1, 2.0 LoRo).
The decoder is able to negotiate capabilities out of the box with downstream an upstream components. If a target speaker configurations is not selected by the user, it’s able to communicate with the audio sink and negotiate the number of output channels.
Dynamically extracts and exposes real-time stream metadata, such as average bitrate, frame rate, active language tags, and dialogue normalization (dialnorm). This metadata is accessible through readable GObject properties and downstream sticky events, making it ideal for professional broadcast monitoring workflows.
Provides granular control over the audio output by allowing users to adjust the Presentation (presentation-index) or the Dialogue Enhancement gain (de-gain).
Includes on-the-fly pipeline changes, ensuring correct and safe element reconfiguration and caps negotiation.
our use cases
These use cases present conceptual examples of how our ideas and technologies could address real-world industry challenges.
As the digital broadcast landscape transitions toward the IP-based ATSC 3.0 standard (NextGen TV), the industry faces a critical infrastructure gap. Unlike legacy systems, this new framework utilizes the same Internet Protocol backbone as major OTT platforms, enabling a hybrid model of over-the-air signals and interactive internet content.
Within this ecosystem, Dolby AC-4 has emerged as the mandatory audio standard, offering advanced capabilities such as immersive Atmos metadata, dialog enhancement, and personalized audio streams.
The transition to Next Generation Audio (NGA) is moving from a premium feature to a global regulatory requirement: United States (ATSC 3.0 / NextGen TV), European Union (DVB-T2 & UHD), Brazil (TV 3.0), South Korea (UHD services).
The rapid adoption of AC-4 by major networks for live sports and high-profile events has created significant technical hurdles. Current hardware and monitoring tools risk obsolescence without a high-fidelity, legal decoding path. Furthermore, legacy decoders are unable to process the complex metadata required for modern audience measurement and immersive audio experiences. The reliance on “experimental” or uncertified decoders in commercial cloud-encoding SaaS environments introduces substantial legal and technical risks for broadcasters and hardware OEMs.
GObject └── GInitiallyUnowned └── GstObject └── GstElement └── GstAudioDecoder └── fluac4dec
audio/x-ac4
Presence – always
Direction – sink
Object type – GstPad
audio/x-raw:
format: { S32LE }
layout: interleaved
rate: 48000
channels: [ 2, 16 ]
Presence – always
Direction – src
Object type – GstPad
gst-launch-1.0 filesrc location=sample.ac4 ! "audio/x-ac4" ! fluac4dec ! autoaudiosink
“active-presentation” gint
Index of presentation decoded by the Dolby AC-4 decoder
Flags : Read
Default value : 0
“ad-gain” gfloat
Gain of an Audio Description audio program component in dB (-120.0 = -inf)
Flags : Read
Default value : 0
“average-bitrate” gint
Average bitrate estimate in bps
Flags : Read
Default value : -1
“complete-main-gain” gfloat
Gain of a Complete Main audio program component in dB (-120.0 = -inf)
Flags : Read
Default value : 0
“crc-error” gboolean
Indicates CRC error presence in the Dolby AC-4 stream
Flags : Read
Default value : false
“de-gain” gint
Dialogue enhancement gain in dB
Flags : Read / Write
Default value : 0
“decoder-speaker-config” GstFluPadsDecoderSpeakerConfig*
Output speaker configuration of the decoder component
Flags : Read / Write
Default value : DLB_PADC_AC4_SPEAKER_CONFIG_5_1_4 (0)
“dialnorm” gfloat
Dialogue normalization value in dB
Flags : Read
Default value : 0
“dialogue-gain” gfloat
Gain of a Dialogue audio program component in dB (-120.0 = -inf)
Flags : Read
Default value : 0
“dolby-sdk-description” gchararray
String with information about the Dolby Pro Audio Decoder SDK used in this decoder
Flags : Read
Default value : Dolby pro audio decoder component (PADC) v2.8.0.2113848202 Dolby pro audio renderer component (PADMX) v3.6.0.2113848202 Dolby pro Audio metadata interchange format component (PAMIF) v4.0.0.179906733 Dolby pro audio input/output structures component (PAIO) v1.2.0.0
“drc-mode” GstFluPadsDecoderDrcSetting*
Dynamic Range control mode for the decoder component.
Flags : Read / Write
Default value : DLB_PADC_AC4_DRC_NONE (0)
“frame-rate” AC4SupportedFrameRates*
AC-4 stream frame-rate
Flags : Read
Default value : DLB_PADC_AC4_FRAME_RATE_23_44 (13)
“iframe-interval” gint
I-frame interval
Flags : Read
Default value : 0
“loudness-practice-type” AC4LoudnessPracticeType*
Indicates the loudness regulation type for the applied loudness correction
Flags : Read
Default value : DLB_PADC_AC4_LOUD_PRAC_TYPE_NOT_ INDICATED (0)
“max-upper-bitrate” gint
Maximum value of upper bitrate estimation to the current Dolby AC-4 configuration, reset by split in the bitstream
Flags : Read
Default value : -1
“music-and-effect-gain” gfloat
Gain of a Music and Effects audio program component in dB (-120.0 = -inf)
Flags : Read
Default value : 0
“num-presentations” gint
Number of presentations in the Dolby AC-4 frame
Flags : Read
Default value : 0
“output-ref-level” gfloat
Target output level in dB, 0 if deactivated, otherwise -7 to -31 dB
Flags : Read
Default value : 0
“presentation-id” gint
Presentation ID
Flags : Read
Default value : 0
“presentation-index” gint
Index of presentation to be selected
Flags : Read / Write
Default value : 0
“presentation-language” gchararray
Presentation language
Flags : Read
“presentation-level” gint
Presentation complexity for the decoder
Flags : Read
Default value : 0
“presentation-summary” gchararray
Short summary of the presentation, combining channel modes, types, and language
Flags : Read
“renderer-bypass” gboolean
Indicates whether or not to bypass the renderer component, and only process buffers through the decoder one
Flags : Read / Write
Default value : true
“renderer-speaker-config” GstFluPadsRendererSpeakerConfig*
Output speaker configuration fo the renderer component
Flags : Read / Write
Default value : DLB_PADMX_TARGET_SPEAKER_CFG_5_1_4 (5)
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Discover how Fluendo integrated Dolby AC-4 decoding into GStreamer through a complete ecosystem.