Bluetooth audio is gaining many followers today. The disappearance of the mini-jack headphone ports on some smartphones, such as the iPhone, has led to audio companies producing high-quality wireless devices. Among Bluetooth audio technology, Qualcomm aptX code ranks high. Besides aptX, SBC and AAC, you need to know Headphone Tech Specs before buying headphones.
What is a bluetooth Codec?
The word codec, when we talk about wireless audio, means the software method of encoding a stream of audio information that is sent wirelessly between two devices. In other words, it is the process by which the zeros and ones of binary digital data are formatted. It is used to transmit stereo audio through a source device, such as a telephone, a computer, television, etc., to a receiver, such as wireless speakers or headphones. Read our Best Gaming Headsets review.
Different codecs send the audio information using different formats, they can also introduce their own compression technologies to maintain a balance between the sound quality and the information package of the audio files. Compression may sound like a negative for lovers of high-quality audio, but it is necessary if we are going to send large files wirelessly.
This means that the variants between the Bluetooth codecs are compatible with different audio devices, as well as providing different connection and sound qualities. All Bluetooth devices support the standardized SBC (Low Complexity Subband Coding) codec, but SBC implementations have varied in quality throughout the history of this technology. To provide greater consistency to users of Bluetooth products, several companies have developed their own Bluetooth codecs, and then license them to other production houses. AAC is one of these formats, a successor to MP3, used by Apple and others. Sony has its LDAC codec and Qualcomm offers aptX.back to menu ↑
AptX, SBC, and AAC codecs, which one is the best?
Codecs are encoding algorithms that compress audio to handle sound packets for fast wireless transmission. The efficiency of the codec determines the quality of the audio information that will be sent. The SBC code is the standard algorithm for most Bluetooth devices. However, this codec has a relatively high latency and can be a bit noisy. The three main codecs that most users will come across are SBC, AAC, and aptX:back to menu ↑
It is the code that is found in most wireless devices and that all Bluetooth headsets that have the A2DP profile (Advance Distribution Profile) It is capable of transmitting up to 328kbps with sample rates of 44.1 Khz. It provides very decent quality audio and doesn’t require a lot of processing. However, the audio can be inconsistent in some situations. This is especially notable when using inexpensive Bluetooth transmitters.back to menu ↑
Similar to SBC but provides better sound quality. This codec is very popular thanks to the Apple iTunes platform. As against, we must mention that it is not very common to find it in headphones.back to menu ↑
Ideal for demanding audio applications as it encodes audio more efficiently and accepts more information than SBC. It has additional variations, such as aptX (LL) and aptX (HD), which dramatically reduce the latency over the wireless connection and improve sound quality. However, it is somewhat limiting because both the transmitter and the receiver must have aptX capability for this codec to work.
Since BestXpot does not have a reliable means to measure the AAC and LDAC formats wirelessly, we have compared the SBC and aptX codes using them with Plantronics Backbeat Pro 2 headphones.
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AptX and SBC sound quality
We find that the standard SBC codec works well for most audio applications. It is not particularly loud, although, in the signal-to-noise ratio, aptX has a greater range of optimal loudness. The audio differences are subtle from aptX but can be noticeable to both expert and critical ears. The resulting measurements, however, for both frequency response and harmonic distortion, are very similar between the aptX and SBS codecs.back to menu ↑
Latency in bluetooth codecs
Latency, or delay in wireless sound reproduction, is where the aptX codec breaks up. The SBS connection has about 100 ms lag, which is noticeable when watching videos and can ruin certain gaming experiences. On the other hand, CSR developed the low latency aptX code to fix these connection problems. The aptX improves the performance of the SBC, but it is the aptX-LL that has a greater impact in terms of results. The aptX-LL codecs were excellent when we tested them by watching some movies and playing some games. This makes the BackbeatPro2 and other headphones that have this technology, ideal options for these activities.
Based on our tests, we have found that codecs have a greater impact on latency than on sound quality. The aptX codec has subtle improvements in sound quality, but the differences are less noticeable than the improved speed when playing audio via Bluetooth.back to menu ↑
AptX codec, why should we use it?
The SBC codec is configured to work with low bitrates, such as 200kbps, which does not offer the best sound quality. In theory, the SBC codec can operate at bitrates up to 345 kbps, and the introduction of A2DP audio profiles enables wireless transfers of audio formats such as MPEG and ATRAC. However, support for these formats is optional and varies between headphones or wireless speakers.
The aptX codec, on the other hand, offers a better signal-to-noise ratio in important frequency ranges, as well as better performance in terms of delays in the Bluetooth connection. This codec exists, in part, to provide guaranteed quality audio on all products that support this format. AptX audio transfers are performed with a 352 kbps / 16-bit 44.1 kHz bitrate. This means 4: 1 compression compared to lossless files and includes enough information to wirelessly carry files equivalent to the best MP3 formats. In terms of smartphones, the standard aptX codec is found in a large number of devices as well as the improved aptX HD, which has appeared in newer wireless devices.
Another interesting aspect of the aptX codec is that it uses a technique called ADPCM (Adaptive Differential Pulse-Code Modulation). Essentially, it divides the audio frequency spectrum into four bands, each with its own bit depth and signal-to-noise ratio. This technology is also superior to SBC when sending audio that has already been compressed via Bluetooth, such as MP3 audio files. The aptX codec has, as we said, a better signal-to-noise ratio than the SBC, about 5kHz more capacity so that we can better perceive the fine details of voices and instruments when we listen via an aptX codec if our material of source has a good quality.
The Qualcomm codec also features a faster conversion speed than the algorithms used by the SBC and can transfer audio packets more efficiently. This means it handles lower latency, an important factor for wireless audio when watching movies or playing games with our favorite consoles. Qualcomm’s low latency technology handles a delay in the region of 40 ms, although this can increase to around 150 ms in older codecs. The SBC is measured with a delay of 100 ms and can increase to 150 ms. The AD2P varies between 40 and 150 ms, depending on the conversion requirements.back to menu ↑
What is aptX HD?
This new Qualcomm format was introduced to make use of fast Bluetooth profiles for better sound quality. It is an evolution of the same ADPCM technology but offers some extra bit depth and less noise when it comes to playback. HD version further improves to compression quality Qualcomm. Although the company claims that the aptX HD codec supports resolutions higher than 24-bit- 48 kHz, this codec is designed for wireless use, so it will not sound lacking in detail compared to uncompressed materials. However, its bit rate capacity is 576 kbps, which far exceeds that of the SBC.back to menu ↑
We can say that the Qualcomm aptX codec has a good number of advantages over the SBC and it is also supported by more than 70% of current Android devices. None of these codecs ensures a guarantee of sound quality if our audio files, as well as our headphones or speakers, are not also of good quality, however, they help to achieve the best possible quality when reproducing sound through Bluetooth technology.