Hey, everybody. I haven't written on this forum once, but I think you all know exactly who I am.
First, I want to thank everyone for using our custom kernel. Jkbuha and I appreciate your feedback and reasonable criticism. Also, we always try to listen to your requests and try never to refuse help if it is possible.
I periodically read messages in Head-Fi, but more often than not I can be found on the 4PDA forum. I decided to write because I noticed that some people had a lot of questions. Well, I can answer them.
I will answer briefly, because if I go into details, I will have to spend more than one day writing this details. I hope you're not offended by that.
1. Bluetooth Sound Transmission : Since the FiiO X5-3 does not support AptX HD codec, we are limited to the AptX codec. It's a pretty old, simple and computationally fast codec, without psychoacoustics, using Adaptive Differential Pulse Code Modulation (ADPCM) that was created in 1988. It differs from AptX HD (which is not present in the X5-3) in that it differs only in encoding parameters. The technology itself has remained the same. The codec has only one parameter - sampling frequency selection. AptX divides the audio into 4 frequency bands and quantifies them with the same number of bits at all times: 8 bits for 0-5.5 kHz, 4 bits for 5.5-11 kHz, 2 bits for 11-16.5 kHz, 2 bits for 16.5-22 kHz (digits for 44.1 kHz sampling rate). When creating the codec, the authors calculated ADPCM coefficients on a set of music files. The closer the audio signal is to the set of music on which the tables were based, the fewer quantization errors (noise) are created by AptX. Because of this, synthetic tests will always produce worse results than music. Despite this, AptX can be considered an acceptable codec for audio streaming. The maximum audio quality parameters for AptX are as follows: 48 kHz \ 16 bit. Is that enough to listen to high quality music without loss - yes. Is that enough for you? It's up to you. Is it possible to say that the majority of modern smartphones transmit sound via Bluetooth better than the FiiO X5-3 - yes. Bluetooth in the X5-3 is not its strong point, but just an extra option.
2. Comparison of sound quality over Bluetooth and wired connection : In this case, it's simple. No, even the newest Bluetooth codecs (Aptx-HD; LDAC; e.t.c) are capable of transmitting audio signal at the same level as wired analogues. For example, LDAC, quite new and actively promoted "Hi-Res" codec from Sony, supports sample rate up to 96 kHz and 24-bit bit rate, with bitrate up to 990 kbps. However, these are the maximum possible reference parameters, which can be achieved only on paper. In reality, things are a little worse. Besides, will come nearer to the maximum parametre of transfer, you can only in that case if both your source and your receiver, work under report Bluetooth 5.0. The maximum output parameters of the X5-3 are much higher than this. Whether it is heard in a real life - yes, as at processing of a sound under report Bluetooth, DACs do not participate.
3. V4A and Magisk questions: Guys, I honestly don't understand why you guys are having this conversation on this topic. I'll answer very quickly. Was it possible to install Magisk on the X5-3 - yes. It was possible a year and a half ago. Was it possible to install V4A on the X5-3, with or without new firmware, or without FiiO Music - yes. As an experiment, I did it myself six months ago. If you were interested in this topic, you could have asked me about it at 4PDA. However, I am glad that those who needed to figure it out for themselves. The only request is that you don't have to put so much pathos into it, because there's nothing more than an ordinary one. Projects V4A and Magisk created a long time ago and there are no problems with their launch on Android 5.1.
4. Deep Sleep Frequences : The frequency in this mode has no constant value. As a rule, it is several times less than the minimum frequency set in the kernel. It is not possible to determine the exact frequency in this mode because it is constantly changing. It changes under the influence of the whole cascade of kernel modules, its scheduler, etc.
5. Overheating on a custom kernel: It is necessary to determine at once that overheating of X5-3 is possible on any kernel. It can happen for many reasons and some of them can be very exotic. For example, the X5-3 may simply burn if you use the free version of the Neutron player. During neutron track playback, when using the free version, sooner or later, music playback will stop. If at this time your player has been locked and the screen has not worked, the neutron output process will hang and will be very heavy on the CPU. As a result, the player can operate at its maximum frequencies for several hours. All this leads to overheating of the player. In RK installed in X5-3, there is no CPU temperature sensor, therefore, there is no trottling mechanism. The temperature is monitored only by the thermo-sensor of the battery and when the battery reaches dangerous temperatures, the player will be immediately switched off and go into protective mode. I have witnessed many similar cases myself during the test.
Returning to the question of overheating on a custom kernel. Taking into account what I have described above, overheating is possible on the custom kernel as well. However, it is often the user's fault alone. Otherwise, they are the problems of the hardware part. We conducted a lot of tests and in terms of scenarios, the custom kernel operating at 1.7 GHz - 2 GHz was colder than the stock kernel operating at a maximum frequency of 1.4 GHz.
There were many more questions about kernel, system processes, hardware parts, etc. Unfortunately, I just can't spend any more time painting all these details now. Besides, I don't see much point in it, because the users asking these questions don't have the necessary knowledge to understand exactly what they're talking about. I beg you not to be offended by this statement. I do not want to offend anyone. Simply, if a person is an engineer or works in similar IT fields, he will not ask such questions, since he already knows how it works. If you really have questions for me about the work of the custom kernel (or any other) you can always ask them in personal correspondence.
The last thing I want to ask is to be a little kinder to each other. We created this project primarily for ourselves, but we do not mind sharing it with others. We do not require money, although we spent more than a year on development, testing, promotion, etc. We do not force you to use our product, for this reason everyone who for some reason does not suit it may not use it. This is exclusively your business. However, if you want to receive feedback from our side, then keep calm and do not go beyond pleasant communication.
I hope that I managed to convey to you my thoughts.
Thank you all again. You all are awesome
P.S. I apologize for the poor level of English. Many here are aware that I am Russian-speaking. However, I tried to be clear
