If it is not Sony's loyal fans, or audiophiles, I am afraid I don't know what LDAC is. Therefore, Xiaobian thinks it is necessary to talk about LDAC, because it is likely to have a major impact on the future of wireless headphones, speakers.
What does ldac mean? What is ldac technology?LDAC is a wireless audio coding technology developed by Sony. It was first unveiled at the 2015 CES Consumer Electronics Show. At the time, Sony said that LDAC technology was three times more efficient than standard Bluetooth encoding and compression systems. In this way, those high-resolution audio files will not be over-compressed when wirelessly transmitted, which will greatly degrade the sound quality.
The reason why Sony's decision is quite interesting is that LDAC technology used to be almost "Sony-only" in the past, only on its own mobile phones, players, headphones, Bluetooth speakers. Because LDAC technology relies on the simultaneous support of audio and speaker systems, this makes the technology a unique highlight of Sony devices. Nowadays, as long as it is a mobile phone with Android O installed, you can use LDAC to let users enjoy wireless HD music on the playback system that supports this technology.
We all know that the sound quality of Bluetooth headsets is generally inferior to wired headsets, where insufficient transmission bandwidth is an important reason. But Zhijun Jun wants to say that the transmission bandwidth is not enough to blame Bluetooth, because after Bluetooth 3.0, the transmission bandwidth has been increased to more than 24Mbps, even if the actual rate is more than half of the loss is much higher than CD lossless music (1.41Mbps) ) requirements. However, the current Bluetooth sound quality still stays at the loss level of MP3, and the main culprit is the transmission protocol.
Bluetooth transmission audio mainly relies on the A2DP protocol, which was established in the early days of the Bluetooth standard. At that time, the current situation was not taken into account, and the amount of data during transmission was limited, so that the audio data could only reach about 328 kbps. So even if the new Bluetooth standard brings more speed, the A2DP protocol is not updated.
Since the A2DP protocol cannot be changed, if you want to improve the sound quality of Bluetooth, you can only start with the optimization of compression and encoding. Based on this, the SBC, AAC, and apt-X coding specifications are generated. Among the three specifications, SBC is the most common, and basically all smartphones, Bluetooth headsets and speakers are supported. The maximum allowable rate of SBC is mono 320kbit/s, dual channel 512kbit/s audio transmission, the algorithm is not good enough, so the sound quality performance is not ideal.
AAC is currently mainly used by Apple. The iPhone and iPad support AAC. Although the supported rate is not much better than SBC, the algorithm is better and the sound quality is improved.
Unlike traditional Bluetooth encoding technologies such as SBC, LDAC does not undergo any degradation when transmitting high-resolution audio content, and allows the device to transmit more data wirelessly for better sound quality. Sony said this is mainly because of "more efficient coding and optimized information packaging."
When transmitting LPCM high-resolution audio, LDAC technology maintains its maximum bit depth and frequency response range, enabling high-quality transmission even at 96 kHz/24 bit audio. In contrast, the traditional Bluetooth audio transmission technology, before transmitting LPCM audio, the first thing to do is to "degrade" the high-resolution video to a CD quality of 44.1 kHz/16 bit, and then transmit it through 328 kbps. In the case of two large loss of information, the final quality is far from the quality of the CD.
LDAC transmission modeLDAC offers three modes of transmission, starting with the quality-first 990 kbps mode, followed by the default 660 kbps normal mode, and finally the 330 kbps mode, which is similar to the normal Bluetooth standard, primarily to ensure connection quality. In the screenshot of the Android O Developer Preview, we can see that LDAC also provides these three transfer modes in the system.
It should be noted that the LDAC transmits the same lossy audio, not lossless. Sony does not deny that it means that the audio after transmission is not "high resolution" and it is called " High quality "audio. However, the official claims that even the loss of information caused by the transmission of LDAC is still much less than the traditional Bluetooth transmission.
The biggest feature of LDAC technology is that it ensures that wireless audio transmission can also have enough information, which is implemented into the actual music sense, that is, the sound is more full. The traditional Bluetooth transmission is dry and poor because of the lack of information, just like listening to the voice without emotion, only some identifiable melody. With the support of LDAC technology, the density and intensity of the sound are higher, the music details are much richer, and the low frequency is more deep, not only the empty amount, but the "texture" is stronger.
Of course, you can't expect the LDAC's sense of hearing to match the wired connection. Considering the difference between the transmission rate and the anti-interference ability of the two, this is not realistic. However, the quality of wireless music in the LDAC environment is indeed very close to wired.
It is worth noting that LDAC transmission does not mean that it can be magical to allow low bit rate audio to exceed its own level, because this technology solves the problem of wireless transmission bandwidth. Therefore, the higher the audio code rate within a certain limit, the more potential of LDAC can be exerted.
However, LDAC has some flaws that have to be said in terms of experience. The first is that its power consumption will be significantly higher than normal Bluetooth. In addition, the quality priority mode of LDAC is easily interfered by wireless signals such as Wi-Fi, and the sound will appear intermittent. At this time, we had to choose a mode with a lower transmission rate.
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