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AC-4 Decoder

Certified Dolby AC-4 audio decoder by Fluendo

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.

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Bringing Dolby AC-4 codec to the open world

legal-compliance

We provide the only Dolby-certified path to AC-4 within the GStreamer and FFmpeg ecosystems.

integration

Seamless Integration

We simplify the complexity of Next Generation Audio, providing a solution for the most widely used multimedia frameworks (GStreamer/FFmpeg).

cost-reduction

Cost Optimization

We enable high-performance software decoding on generic hardware, eliminating the need for expensive, specialized DSP chips.

FEATURES

Dolby AC-4 decoding

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.

Integrated Dolby Renderer & Bypass

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).

Automatic caps negotiation

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.

Real-time UI-Metadata Extraction

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.

Audio Customization (Presentation selection, de-Gain & drc)

Provides granular control over the audio output by allowing users to adjust the Presentation (presentation-index) or the Dialogue Enhancement gain (de-gain).

Runtime Reconfiguration

Includes on-the-fly pipeline changes, ensuring correct and safe element reconfiguration and caps negotiation.

About AC-4 Decoder

How the AC-4 decoder works

Hierarchy

GObject
└── GInitiallyUnowned
    └── GstObject
        └── GstElement
            └── GstAudioDecoder
                └── fluac4dec

Pad Templates

  • sink
audio/x-ac4

Presence – always

Direction – sink

Object type – GstPad

  • src
audio/x-raw:
         format: { S32LE }
         layout: interleaved
         rate: 48000
         channels: [ 2, 16 ]

Presence – always

Direction – src

Object type – GstPad

Example launch line

 gst-launch-1.0 filesrc location=sample.ac4 ! "audio/x-ac4" ! fluac4dec ! autoaudiosink

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Bringing Dolby AC-4 to GStreamer: the journey to decoding

Bringing Dolby AC-4 to GStreamer: the journey to decoding

gstreamer, codecs, upstreaming, the-lab, open-source, ac4-decoder, ffmpeg-enabler-dolby-professional

Discover how Fluendo integrated Dolby AC-4 decoding into GStreamer through a complete ecosystem.

Read more