In a bid to deliver better audio, Netflix is upgrading its existing HE-AAC audio codec with the extended HE-AAC codec which is xHE-AAC.
The Extended HE-AAC audio codec is said to fix three prime problems associated with the audio experience.
- Sudden Volume Change
- Sound in Noisy Environments
- Audio Quality on Slower Mobile Data Connections.
Okay, let me explain these three to give you an idea of what the xHE-AAC audio codec is doing.
Sudden Volume Change
While some of you might not know, let me tell you, the Dynamic Range of Different programs varies from one to another.
What is Dynamic Range?
The Difference between the quietest and loudest sound of a program is called Dynamic Range.
For example, the dynamic range of an Action movie is different from that of a Drama Movie.
In the below figure, you can see the dynamic range of different genres.
In the figure you can see that the dynamic range of an action genre, say a movie ranges from 0 to -60 dBFS. The same for the documentary is from -5 dBFS to say -65 dBFS and so on.
In the above figure, do you see the black lines?
Well, that indicates the Dialogue Level.
Now, what dialogue level is, it is the most important element in the program from the viewer’s perspective.
Now, in the above figure you can also see the dialogue level also varies from one genre to another leaving room for the user to burden for switching up and down of their device’s sound while viewing one genre to another.
The xHE-AAC codec overcomes this issue by normalizing the loudness of dialogue level in different genres like as shown in the figure below.
Improving the audio in Noisy Environment
Above we talk about Dynamic Range that counts the lowest and highest sound of different genres.
Now, let me tell you that, Different Devices also have different dynamic ranges.
Sometimes, the dynamic range of the content is higher than that of the user’s device.
That leads to open space for Noise. In that case too, the xHE-AAC codec has been made such as to cover that issue.
The xHE-AAC codec solves these issues with a good Dynamic Range Compression Algorithm.
Maintaining the Audio Quality in Slower Mobile Data Connection
In India, where most users are on the Mobile plan or Streaming the Netflix content on their Mobile, the xHE-AAC codec is also said to help them to get better audio quality.
The xHE-AAC codec is said to adapt the quality of Internet Connection.
In slower internet connections, it adjusts the audio bit rate in such a way to provide the best sound quality to the user.
The above all the three improvements of the audio quality in Netflix is part of improving the loudness management of the content available on Netflix.
The xHE-AAC audio codec which is also called the MPEG-D DRC is said to overcome all the three issues.
Source: Netflix Tech Blog