Qualcomm Qualcomm is the most well-known processor and chip solution hardware provider for ARM architecture on Android smartphones. The QSD8250 in Qualcomm's Snapdragon series is the first ARM processor to achieve 1GHz clock speed. In Android phones, Qualcomm's solution is the most common, and Qualcomm chipsets have relatively good compatibility in the confusing Android products. However, after testing our mobile phone with Qualcomm chips, it found that its audio subsystem was defective. And this flaw, in the Android system, is just and unfortunately ruthlessly enlarged. We tested a total of six Qualcomm chips including Motorola XT316, Huawei U8800, HTC Desire Z using the same chip, HTC Desire HD, Lenovo Le Pad, HTC Sensation and a special HTC HD2 [QSD8250 WM6.5WP7Android 3 operating system]. Mobile phone or tablet, covering Qualcomm from ARM11 to all series of Snapdragon chips [not including different models of mobile phone network standards, such as CDMA network]. They all have the same problem. What is the reason for the Qualcomm Snapdragon full range of such problems? What impact does it have? Why is the problem with Qualcomm products that match Android? Let's analyze them one by one.
Qualcomm + Android = sound quality tragedy?
Our test objectives and methods
Finding the flaws in the Qualcomm chipset audio system is certainly not the purpose of our testing. We have not been able to find chip-level design flaws for no reason. Since 2010, Soomal has been testing headphone amplifiers, sound cards, etc., and we have been insisting on using a fixed set of test methods to objectively analyze and test the signal output capabilities of test objects. Although this set of test methods cannot fully judge whether its system is excellent enough, the judgment of system defects is accurate from the principle, process and objective results. You can easily understand that if there is a major deviation from the spectrum of the 20Hz-20KHz frequency sweep signal we tested, its system must have problems, the sound performance is not good, and as to the seriousness of the problem, it can also be caused. Analyzed by some features. When we tested the first and even the third Qualcomm chipset phone, we did not determine its problem, but through Windows Phone 7, Windows Mobile system, we finally finalized the conclusion. Of course, we found that the problem was not to hit Qualcomm, and the mobile phone using Qualcomm chips, we just raised the question and fortunately found the cause of the problem. As Qualcomm, it is not too difficult to fix this defect.
In order to read the article better, we will next explain the reading method of the frequency sweep spectrum.
Frequency sweep test standard signal - 20Hz-20KHz
As shown in the figure, you can see two lines with a certain angle divided into upper and lower parts [representing left and right channels], which exist in a two-dimensional coordinate space whose abscissa is the time ordinate and the frequency is frequency. It represents an optical spectrum analysis of a standard test signal. It is a sine wave scan from 20Hz-20KHz, and we set the whole process time to 10 seconds. The intensity of light represents the strength of the signal. Because everyone saw this picture is the standard signal we generated, so we found that there are only two bright lines, and no other weak signals appear, and everyone notices that its background is very dark, which means the entire frequency range The noise is very, very small.
Let's look at another picture, which is an analysis of the results from the recording of the above test signals from the iPod Classic. Compared with the original signal, it appears a straight line with a different slope from the main signal. This is a harmonic, but everyone observes its color, which is light blue, indicating that the signal strength is very weak. Compared with the original signal, it is also found that some low-frequency red-light noise appears in the low-frequency part of the coordinate. You can also see a slightly larger harmonic distribution than the iPod Classic in our tested MP3 players, headphone amplifiers, etc., but all are within acceptable limits. Understand our test methods, let's take a look at the performance of Qualcomm's chipset.
Our tests were performed using professional-grade sound card entry and tested using both RMAA software testing and frequency sweep signal spectral analysis. Here, we do not list the test results of RMAA, we can refer to the sound quality evaluation report of each mobile phone, and we enumerate all the frequency spectrum analysis charts we have tested Qualcomm chipset. As the image scaling becomes smaller, we zoom in on one to illustrate their characteristics. It should be noted that these tests are all done under the 16bit 44.1KHz specification.
Qualcomm Qualcomm chip audio subsystem frequency scanning spectrum
HTC Desire HD [T-Mobile G10] Smartphone - Frequency Scan
It is easy to find from the pictures that the noise of all Qualcomm chips has the same special distribution law. This kind of law has never appeared in all the products we have tested in portable players, sound cards, amps, etc. This kind of law is mainly manifested in the fact that it will have a noise distribution parallel to the main signal, and the noise intensity is strong, and the noise distribution in the middle and high frequency parts also starts to be disordered. We were not sure at first that this was a problem with Android or a problem with Qualcomm. Until we do the following two tests. First, we found that the machine results of Tegra2, AML8706 and other chips tested under the Android system with 44.1KHz signal have no similarities with Qualcomm chips; secondly, from "God Machine" HTC HD2 in Windows Phone 7 and Windows Mobile 6. 5 test.
HTC HD2 Phone 7 - Frequency Scan @16bit 48KHz MP3
HTC HD2Mobile 6.5 - Frequency Scan @16bit 48KHz
The test chart seen here is different from the test environment of the previous two, but it is the same as the test environment in the above figure. It is the result of the HTC HD2 mobile phone playing the 16bit 48KHz test signal under Windows Phone 7 system. The same is the QSD8250 chip of the HD2 mobile phone, but the unique noise distribution of the Qualcomm chip disappears. We saw a very normal frequency sweep spectrum. The reason is very obvious, the Qualcomm chip has a 44.1KHz SRC problem in the hardware part. If you still believe that HD2 is because of cracking the running Windows Phone 7, then look at the performance of HD2 under the native system Windows Mobile 6.5, the result is consistent with Windows Phone 7.
Schematic diagram of Qualcomm audio subsystem in Android2.3
Schematic diagram of Qualcomm audio subsystem @Android2.2[and lower version]
You may have discovered how the problem happened. From the work flow chart, the software in the system plays the program source, and the signal is forwarded to the operating system driver layer. After the operating system outputs, the hardware part is finally output. In the Android phone of Qualcomm chipset, if the Android system encounters 48KHz signal, it will force SRC to 44.1KHz, and then hand it to Qualcomm chip. Qualcomm chip hardware encounters 44.1KHz signal, and then forces SRC to 48KHz output. This is the most tragic process. When you play a video, most of them will encounter this situation, because most of the audio tracks in the video currently use the 48KHz sampling standard. In another case, the program source of the software is 44.1KHz, Android support, naturally no problem, but the Qualcomm chip hardware layer does not support, it still has to force SRC to 48KHz output. So, I saw the tragedy of the test "family portrait" that we provided.
HTC Desire HD [T-Mobile G10] Smartphone - Frequency Scan @16bit 48KHz
Whether the Android operating system forces the SRC or the Qualcomm chip to force the SRC, it will bring significant signal loss and a lot of noise. Android SRC problem is obviously more serious than Qualcomm, but Qualcomm chip does not support 44.1KHz output, the forced SRC occurs, although it is far better than the Android operating system software from the SRC process, it is still obviously flawed and insufficient. As a chipset used by so many mobile devices, it is impossible to support the 44.1KHz standard adopted by the most common music products, and support is provided by SRC. All 44.1KHz signals are output through the SRC, which needs to be calculated by the processor. It must increase the power consumption of the chip. This design is really unrewarding. Maybe Qualcomm's chipset, I thought that my advantage is at 48KHz, then there will be no problem when playing video. unfortunately! Qualcomm chip hardware on Android is unable to get it.
Qualcomm chipset issues affect
Motorola Motorola XT316 Smartphone - Qualcomm Qualcomm MSM7227
HTC Sensation Z710e [G14] Smartphone - Disassembly - Qualcomm MSM8260 Processor
From the Qualcomm chipset design, perhaps Qualcomm is aware of the importance of support for the 44.1KHz specification [the average person will realize], but choose the wrong solution. In hardware, using SRC to achieve, not only consumes processor resources, but also does not get enough sound. In the native support of 48KHz, the Android system took the lead in SRC to 44.1KHz. Therefore, regardless of chip energy saving or output quality considerations, Qualcomm should change this approach.
From the existing Android phones or tablets using Qualcomm chipsets, due to Qualcomm chip hardware defects, their sound performance is not as good as a relatively low-end MP3 player with a relatively low performance of about 200 yuan. Compared with our evaluation of the Sigmatel STMP3770 player, there is a clear gap. And if the flagship model like HTC, Lenovo, the opponent is positioned on the Apple iPhone, iPad, it can only be powerless, and easily injured [I thought it was the design problem of Le Pad].
From the perspective of audio and video playback, although Qualcomm hardware is fully prepared [video file track is mostly 48KHz]. However, the problem of forced SRC will occur in the Android system. The degree of signal degradation is very obvious in this process, and it is more obvious than the Qualcomm chip to the extent of subjective hearing. As for those "Smart TVs" that are intended to be built on Android, such as Google TV, Samsung Smart TV, Hisense Smart TV and other smart TV products. They all play video content based on the network and the player inside the system, they will have good results? We are not sure, but the possibility of not having problems is small. If this problem really exists, is this not a fatal flaw in the Android smart video system?
to sum up:
There is no doubt that Qualcomm currently has audio system defects in its full range of chips. From an objective point of view, this gap is relatively obvious compared with competitors, and because the problem occurs at the hardware level, it brings downstream product design and manufacturing. Unable to solve the difficulties. In principle, it is not only of poor quality, but also not conducive to energy saving; from the subjective sense of hearing, its performance can not reach the level of entry portable player. The combination of Android system and Qualcomm chip makes this problem even worse. This shows that there are design flaws in the hardware and operating system of one product, which will make the related applications unable to expand. Regardless of whether Qualcomm or Android, such an error should not be, and the long-term uncorrected, even in the latest version of the hardware [MSM8260] and software [Android 3.0], the problem solving time is greatly delayed .
Although the deficiencies of Qualcomm and Android are not enough for most users to give up and choose other products, we also see that NVIDIA, TI, Marvel and other chips do not have related problems, and Windows Phone 7 is also ready. From the most basic point of view, for a function that already has and has a high usage rate, a low-energy solution should not occur from a design perspective; in the long run, if these details are not going to go To solve it, it will definitely cause a fatal blow when there is a product that is competitive enough.
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