Exploring Qualcomm’s aptX Bluetooth codec Part 2
In the previous part of this series, we talked about Bluetooth codec and aptX. In this part, we will talk about aptX HD and some compatibility issues surrounding aptX.
Bluetooth codec have various variations and nowadays, aptX is very popular. So let us have a look at aptX HD.
Qualcomm has introduced new aptX HD format. This format is useful for faster Bluetooth profiles, offering superior audio quality. ADPCM technology has evolved into something bigger, faster and greater. However, it offers noise performance in each of the sub-bands by offering extra bit-depth.
By increasing the bit-depth of these frequency bands by 2 extra bits, aptX HD has improved the quality of Qualcomm’s compression. It has ushered the the bit-depth in the four bands up to 10, 6, 4, and 4 bits, respectively.
Despite claims by Qualcomm of aptX HD supporting higher resolution 24-bit and 48 kHz sample rate audio files, this codec is still based on average compression technology. Apt HD can manage 576 kbps, surpassing the capabilities of Sub-band Coding (SBC).
Compression technologies used by aptX
aptX’s compression technology uses a technique called split-band Adaptive Differential Pulse-Code Modulation (ADPCM). This technique splits the audio frequency spectrum into four frequency bands. Each band has its own bit-depth and therefore, signal-to-noise ratio. This technology also facilitates the transmission of quantization difference between the original sample and the next predicted sample. In the end, ADPCM is more transparent technology for sending audio.
ADPCM is very different from masking models used by masking models used by audio formats (like MP3) and SBC. There have been tests that prove show that aptX has a better signal to noise ratio below 5 kHz than SBC, frequencies housing the majority of musical audio content.
Qualcomm’s codec can have a conversion rate, faster than the modeling algorithms that are used by SBC. It can transfer data packets more efficiently. In simple words, now users can convert their audio into aptX format, send it and decode it at a faster rate now. This causes lower latency for wireless audio when it comes to watching video content that requires lip syncing.
Latency falls somewhere in the region of 40ms if the codec is not totally compatible.
Compatibility issues surrounding aptX
Some smartphone handsets do not support Qualcomm’s Bluetooth standard, even though the hardware may appear same as the hardware of other models. Although, Snapdragon platforms have included all of the integrated Bluetooth codecs, many Android phones are yet to expand their horizon of compatibility.
Ease of enabling the features in software is also an important issue. The licensing situation is similar with Qualcomm’s WiPower, Quick Charge and in-house camera features.
Apart from Qualcomm, Sony’s LDAC also faces similar issues. No technology guarantees good quality if the user’s source material (speaker/headphone) is not good. However, aptX ensures that Bluetooth is not a bottleneck.
Have you ever faced any compatibility issues? Post your comments, expressing your thoughts and the remedies you know.
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