Exploring Qualcomm’s aptX Bluetooth codec Part 1

Exploring Qualcomm’s aptX Bluetooth codec Part 1

Not only we love listening to music on our smartphones, we also love the convenience that we are speaking on a microphone connected to Bluetooth earpiece and our phone is kept on table few steps away.

Bluetooth audio is gaining traction in smartphone space. 3.5 mm audio jack is passé for some models. Manufacturers continuing to produce better and more advanced wireless headphones.

Hence, it is normal to hear and expect updates about unique upgrades being made to various wireless audio technologies.

Qualcomm’s aptX codec is something that can be quoted as a relevant example to discuss this phenomenon. In this part of this two-part series, we will understand the concept of Bluetooth codec and aptX.

What is Bluetooth codec?

Codec is defined as a device or program that compresses data in order to enable faster transmission and decompresses received data. In the present context, this word is being used in the context of audio compression.

Audio codec is a software method of encoding and decoding digital data that is sent being exchanged wirelessly between two devices. The digital data sent is in the program language of 1 and 0. Once received, it is decoded into the language that person using the receiving device understand.

Variations of Bluetooth codec

There are different formats and standards used by different codecs to send audio data to compatible devices. Codecs can also introduce their own compression technologies that enable them to balance sound quality against package size. Bluetooth is a slow wireless standard. That is why, the need for audio compression can never be denied when the data has to be sent over Bluetooth.

Majority Bluetooth codecs are compatible with different hardware. They can also affect (or cause differences in) latency, audio quality and connection quality. All Bluetooth devices are compatible with standard Low Complexity Sub-band Coding (SBC) codec by default.

However, there have been wide variations in the quality of historical implementations of codecs. Some companies have developed their own Bluetooth codecs in order to ensure more consistency to users. Many times, these codecs are licensed out to other hardware companies. For example, Apple offers AAC as successor to MP3. Sony offers LDAC and Qualcomm offers aptX.

Apprehensions surrounding aptX

Qualcomm’s aptX has been helpful in addressing some of the consistency problems because its default SBC codec is supported by all devices. Now SBC has been configured for low variable bitrates. 200 kbps for audio does not provide the best sound quality.

Better bitrates like 345 kbps are required for the smooth functioning of SBC. Now that A2DP profiles have been introduced, direct wireless transfers of ATRAC and MPEG audio formats has become possible. Support for these features is anyways optional and varies from device to device, including wireless speakers and headphones.

aptX provides consistent audio quality, along with guaranteed feature set across all compatible products. It has the ability to transfer audio at a set 352 kbps bitrate for a 16-bit 44.1 kHz stereo file. Sending a compressed file (instead of an uncompressed one) with a 4:1 compression ratio and enough data is almost equivalent of top notch MP3 file over the air.

Comparison of bitrate is not a sure-shot way consider the feasibility of sending the audio as other factors that are needed to be considered are compression methods and every type of compression does affect the audio quality.

Share your thoughts about codec and aptX by posting comments below.

In the next part of this series, we will explore aptX HD, compression technologies used by aptX and the compatibility of aptX.

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