Chrome Receiving Support for EAC-3 (Dolby Digital Plus) Passthrough
Chrome will receive support for Dolby Digital Plus (also known as Enchanced AC-3) passthrough in an upcoming update, as can be seen on the Chromium Gerrit. This is a huge addition for those using Android TVs with a sound system which uses Dolby Digital Plus. Dolby Digital Plus is an advanced surround sound audio technology that has found its way into many home devices, including home theaters and car sound systems.
The commit description is as follows:
When the connected HDMI receiver supports (E)AC3 passthrough, we can directly pass raw compressed (E)AC3 bitstream to AudioTrack.
This addition is beneficial to audio enthusiasts, as this means you no longer need to rely on the device running Chrome to decode it. Instead, you let your preferred audio system do all of the decoding and rendering of the audio data that it needs to do. This should usually lead to enhanced audio quality, as the device will be optimized by the manufacturer for the best audio quality on the Dolby Digital Plus device. This upgrade is especially important for Android TVs, as they are the most likely to be outputting to a sound bar or other Hi-Fi devices supporting this.
The raw audio part refers to audio before it’s processed. When the system processes audio, sometimes it may apply equalization, compression or loudness-boosting in certain frequencies. These are to provide a “better audio experience” but may actually be a detriment to the enjoyment of someone with a high-end system that can do its own decoding and processing. Providing the already-processed audio to an EAC-3 enabled device would be defeating the purpose of such a device. Dolby Digitial Plus, for example, supports up to 5 audio channels at 640kbps, while Android TV if playing from an older version of Chrome will feed 320kbps in a single audio channel to the device, as the device will do the processing and then output to the sound system. For audio enthusiasts this is a huge addition, and also means anything using Chrome custom tabs will get the same treatment.
Source: Chromium Gerrit