Netflix introduces various improvements from time to time to offer a better viewing experience on its platform. Last year they announced a new way of encoding the image that allowed to offer the same quality in half the bandwidth, and now the improvements will reach the sound section.
AAC , stands for Advanced Audio Coding , is a family of codecs that are part of MPEG , and are used in many devices, apps and platforms today. This format removes some audio data to provide the highest possible level of compression without noticeable loss. It was designed as the successor to MP3, offering more sound quality than this format at the same bitrate. Over time, improvements have been released to the AAC codec, such as:
- LC AAC – Low Complexity AAC
- HE ACC – High Efficiency AAC
- xHE ACC – Extended High Efficiency AAC
Each of these codecs offers improvements in the use of bitrate. HE AAC, for example, allows for good compression when the audio bitrate is very low. The most recent of all, xHE AAC, has also been developed by the Fraunhofer IIS, known for standardizing creating many of the coding standards that we use today.
xHE AAC: the ideal audio codec for Netflix
The last of these standards is xHE AAC, which improves the quality of the sound we listen to in streaming. The HE AAC codec works well at compressing frequencies related to speech, but it doesn’t do a great job with music. For this reason, xHE AAC uses two different codecs, one for the melody and one for the voice. In addition, it allows you to dynamically adapt the bitrate when you are receiving content, adapting it continuously without interruptions, making it even more suitable for streaming. If you have a mobile with Android 9.0 or later, your device supports this codec.
For this reason, Netflix has licensed the use of this codec from the institute to use it in its entire catalog of movies, series and documentaries. Netflix has set two of the characteristics of this standard to apply it on its platform.
The first is the possibility to enter specific metadata for the content and adjust the dynamic range of the sound by dividing the sound for different frequencies. Thus, in a living room you can enjoy the full range of sound, but on a mobile phone in a noisy environment such as a car or an airplane, there are frequencies that become more difficult to hear correctly. With the introduction of MPEG-D metadata, content can be tailored to be played in the best possible way on mobiles and televisions.
The second is the obvious improvement in sound quality when the bitrate is low , and being able to do it in an adaptive way as we have commented to reduce mobile data consumption .
The bottom line is that Netflix’s sound quality is now going to be better both at home and away, and with a lower bitrate, with a similar goal for implementing codecs like AV1 or HEVC .