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When talking about MP4 players, we first need to explain what MP4 is. MP4 (also called MPEG-4) is a type of MPEG format and a compression method for moving images. This compression provides higher image quality with smaller files and is currently one of the most popular video file formats, especially on the web. It is a compression standard for ultra-low bit-rate moving images and languages. It is used for real-time image transmission with a transmission rate lower than 64Mbps. It can not only cover low-frequency bands, but also develop towards high-frequency bands. MP4 provides a broader platform for multimedia data compression. It defines more of a format and an architecture rather than a specific algorithm. It can make full use of various multimedia technologies, including some tools and algorithms of compression itself, as well as image synthesis, speech synthesis and other technologies. MP4 has attracted widespread attention since the day it was proposed. Currently, the most popular compression methods used in MP4 are DivX and XviD. DVD programs that have been processed by MP4 technology represented by DivX or -ROM to save generated files. If the requirements are lowered, one disk can hold a movie of 100 minutes, and the picture quality at this time is still significantly better than VCD.
The concept of MP4 players is not completely unified. Some people call it PVP (Personal Video Player, personal video player), while others call it PMP (Portable Media Player, portable media player). Many manufacturers have launched of such products. But in general, it can be considered that an MP4 player is a device that can be carried in a jacket pocket and connected to a computer or camera through a USB or IEEE1394 interface. It is easy to download various streaming media to the device. And can smoothly play videos, view images and listen to music digital products. It can be said that MP4 players are the development direction of MP3 players. After adding the playback function of dynamic/static images, they are likely to become the ultimate weapon for people's entertainment life. In fact, many high-end PDAs can support video playback, and their functions include MP4 players. Just like some PDAs or mobile phones also include the function of MP3 players. With its dedicated functions, stable performance and low price, MP4 can also find suitable development space in the market.
What is MP4? MP4 concepts are fully explained in depth!
Observing the current development of consumer electronics (CE), the MP3 player has gradually expanded its territory in the CE market due to its mature technology and affordable price (now 256MB only costs less than 500 yuan). Whether it is diversified policies such as FM broadcasting, repeat playback, synchronization of lyrics and music, and recording, or the integration of OLED (Organic Light-Emitting Diode) screens, Bluetooth (Bluetooth) and other designs, the MP3 Walkman is even more powerful. However, with the rapid increase in shipments, the MP3 Walkman is bound to encounter problems such as market saturation and declining gross profit in the future. Moreover, it can only be used for listening to music and has not yet included the video part, making PMP (Portable Multimedia Player, handheld multimedia player) concept came into being.
When it comes to portable video browsing, with the help of MPEG4 technology, it is easier to strike a balance between storage capacity and playback quality, so much so that some mobile phones and PDAs can already provide it. However, after all, the former is still mainly based on phone functions, and with limitations such as screen size and power supply, multimedia playback can only be regarded as added value.
In fact, the reason why most portable devices such as MP3 players, mobile phones and PDAs use flash memory is simply due to size constraints, but it also has the disadvantage of high unit storage costs. However, thanks to advancements in hard drive technology, the problem of not being able to balance appearance size and capacity has long been solved, such as the Microdrive (miniature hard drive) launched by IBM that year. Today, not only 1.8-inch and 2.5-inch mini hard drives have a minimum of 20GB, but also products such as Apple iPod and Creative Zen Touch have overturned the shortage of MP3 player storage space, making it possible to design and produce PMP.
PMP hardware architecture
Since it is a full-time multimedia entertainment tool, although it looks similar to a PDA, in the face of numerous audio and video formats, the hardware encoding (Encode) and decoding ( Decode) ability is the focus of PMP design. At present, the development of PMP is still in a state of fragmentation, but major chip manufacturers such as Intel and TI (Texas Instruments) have released PMP demonstration architectures through their embedded processor technologies.
Among them, TI's reference design has been used by iRiver, and Microsoft, the leader of PC operating systems, also has attempts to intervene in this market, launching the so-called PMC (Portable Media Center), which is essentially the same as PMP and is in line with PMP. Innovation (Creative Labs) cooperation. In addition to the aforementioned brands, Freescale also has a PMP reference platform, named "Jazz", which has its own i.MX21 (MX=Media eXtensions) processor built-in, and the core of the processor is based on ARM ARM926EJ-S design.
Basically, at this stage, many of the internal core architectures of PMP use a CPU paired with a DSP (Digital Signal Processor). The DSP is responsible for Decode/Encode work; the CPU is responsible for file management and storage. Fetch, and process using interfaces, control of peripheral components, etc. However, DSP and CPU can only be regarded as the main units of PMP. In addition, components such as hard drives, memory cards, and LCD monitors need to be integrated, and the matching with external USB interfaces and control buttons are key considerations. At the same time, in order to move the PMP function towards diversified applications and support different image sources such as digital cameras, TVs and DVD players, it also increases the difficulty of PMP design.
In view of this, in order to meet the above requirements, the PMP design also needs to have a built-in video encoding/decoding chip for conversion between analog and digital signals. In addition, the bus used to connect the video decoder and DSP, the drive circuit of the LCD display, or the communication between the IDE interface and the hard disk control chip, these design points are also indispensable. The following will be based on the block diagrams proposed by Intel and TI.
Intel Demonstration Architecture
The demonstration platform proposed by Intel is centered on its own XScale PXA255. The processor was released in March 2003 and is available in three different timing versions: 200, 300 and 400. It is produced using a 0.18 micron process and is packaged in a 256-pin PBGA. At the same time, in 400MHz mode, the system bus clock can reach 200MHz, which enhances computing performance.
In addition, it has a built-in memory controller with internal and external bus widths of 16 and 32 bits respectively, and supports 2.5V SDRAM. This example uses 64MB PC100 SDRAM, and the PXA255 is not as common as the PXA26x series. It has flash memory itself, so you can also find external 32MB StrataFlash or 2MB Boot Block Flash.
Then look at the peripheral compatibility section, including memory card specifications such as SD, MMC, and CF, as well as support for PCMCIA and MiniUSB (USB2.0) interfaces.
In terms of sound, the Philips UCB1400 integrated chip is used, which covers AC97 sound encoding/decoding and touch screen (Touch Screen) controller, and then the LM4880 chip is used to amplify the audio signal. Then output it to the headphone or speaker. In addition, the controller that drives the LCD screen belongs to the QVGA (1280×960) standard and provides LED backlight. As for the TV output, a Chrontel chip is selected to convert the signal to the NTSC standard, using an RCA connector.
TI Reference Platform
TI’s PMP design features focus on TMS320DM342, integrating C5409 and ARM926. In other words, the CPU and DSP are simultaneously integrated into the DM342 core Inside. Overall, the structure is similar to Intel's design. It also uses 32MB or 64MB capacity SDRAM and 4MB flash memory to load and store the operating system. The difference from the Intel architecture is that DM342 itself has built-in LCD driver and USB2.0 OTG interface controller, and allows CCIR-656 format signals to be transmitted between the video decoding chip and DM342 through the bus. And because the NTSC/PAL encoder is also integrated, composite video output can be directly performed.
On the other hand, DM342 can also support the connection of CCD/CMOS photosensitive components, making it easier to introduce DSC, DV and other functions into PMP in the future. As for the compatibility of memory cards, in addition to the current mainstream CF, SD and MMC, it also includes Memory Stick. In addition, it provides 2 sets of RS232 serial ports and 1 set of JTAG interfaces to complete the support for peripheral devices.
In addition, in addition to computing power, power consumption is also an important aspect to consider for the CPU and DSP used in portable devices. Since the existing x86 technology cannot meet the requirements, embedded cores such as Intel XScale PXA255 and Freescale i.MX21 are all ARM designs. From different perspectives, power consumption not only represents the length of battery life, but also reflects stability and cost. For example, in order to be portable, PMPs are often required to be thin, light, and short. If the processor consumes too much power and causes heat to rise, additional R&D costs will inevitably be spent on heat dissipation. Therefore, how to control power consumption has become another challenge for DSP manufacturers.
Generally speaking, the most direct way to reduce power consumption is to improve the semiconductor manufacturing process and achieve power saving through more advanced transistors and logic components. In addition, when performing I/O operations, the required voltage is usually higher than that of the processor core. Therefore, when the bus is idle, it can also be obtained by turning off the external clock in a timely manner and cutting off the power supply of peripheral components. Considerable power saving effect.
MPEG-4 Codec
Almost all PMP products born today claim to support MPEG-4. Putting aside the numerous format disputes on the side, in terms of encoding and decoding methods, in addition to relying on the powerful computing power of DSP and CPU to complete it in pure software mode, there is also a solution to match the MPEG-4 Codec chip. In fact, the current MPEG-4 Codec market is full of contention, such as existing MPEG-2 manufacturers such as LSI, CirrusLogic, ESS, Broadcom, or consumer electronics-based companies such as Philips, STM, Panasonic, Toshiba, NEC, etc. All. Of course, there are also many new entrants in this market, such as WIS, Vweb, Divio and SandView.
Next, we will explain the products of WIS, TI, Toshiba and Vweb.
1. WIS: Since the MPEG-4 chip launched by WIS tends to be simplified in structure, the price is relatively low, and its compression and decompression are not mainly for entertainment, so the main focus is on In the field of Surveillance. The picture output of WIS's MPEG-4 Codec is WISmp4 specification, and it also supports Divx. It can provide DVD pictures at a bandwidth of 2Mbps. Even at 40Kbps, it can reach the level of QCIF (176×144 pixels), and is monitored by multiple System manufacturers all use WIS's G07007 chip.
2. TI: TI’s MPEG-4Codec product is famous for its encoding/decoding quality, and can execute 3 D1 Channels at the same time, and even covers the TV Encode function, claiming that the picture level is not inferior. in MPEG-2.
3.TOSHIBA: TOSHIBA's product in this area - TC35280XB, is suitable for mobile devices, digital broadcasts and video phones. TC35280XB is produced using a 0.13 micron process and has four built-in RISCP processors, two of which are used for encoding and decoding audio and video data, and the other two are responsible for streaming multi-tasking and filtering noise. When the operating frequency is 60MHz, this chip can encode/decode the QCIF format up to 15 frames per second, and simultaneously perform AMR voice encoding and multi-task processing of H.233 audio and video data. If applied to an MPEG-4 browser, it will have a 125MHz operation speed for CIF data, and also have a 15/S encoding/decoding speed.
4. Vweb: Take Vweb's VW2010 as an example, it uses a 0.18 micron process and supports full-screen MPEG-4 video, including MPEG-1, MPEG-2, H.263mMP3, AAC and Dolby AC- 3 and other audio and video formats. In addition, the output supports MPEG-1 System Stream, MPEG-2 PS/TS, MPEG-4 encapsulated in MPEG-2 TS, PES, ES, and the internal design is relatively complex, equipped with 4 RISC processors, and is locked in entertainment applications, Consumer electronics market.
Storage media
At the hardware level, in addition to embedded processors and MPEG-4 Codec, the growth of hard disk technology has also contributed to the realization of PMP. At present, small hard drives, whether 2.5-inch or 1.8-inch, generally provide a capacity of 20 to 40GB, solving the storage problem of accommodating large amounts of audio and video data. Microsoft once said that with a 40GB capacity, PMC can play 175 hours of videos or 600 hours of songs.
Today's technological development of small hard drives such as 1.8-inch and 2.5-inch is almost exclusively based on Japanese brands such as HITACHI, FUJITSU and TOSHIBA. Not long ago, HITACHI released a new 1.8-inch hard drive, emphasizing features such as small size and easy installation, and focusing on the consumer electronics market. Among them, the Travelstar C4K60 series uses the ZIF connection specification to replace the long-standing IDE interface. The area is 54×70mm, which is about 10% smaller than the previous generation product, and weighs only 46 grams.
Since ZIF connectors are connected to devices via wire sets, they allow PMP manufacturers more flexibility in assembly. Not only that, the ZIF connector is made of soft material, so it is suitable for folding design, which separates the PCB board from the hard drive, integrates the PCB board and LCD panel in one place, and configures the operation buttons and hard drive on the other side, thus Made more frivolous.
As for another microhard drive manufacturer - TOSHIBA, Toshiba focuses on capacity. MK6006GAH was born in the third quarter of this year, reaching 60GB in one fell swoop, with the same rotation speed of 4200RPM and a 2MB buffer. On average The seek can reach 15ms, supports ATA100 specifications, has a size of 78.5×54×8mm, and a weight of only 62 grams. However, from the perspective of PMP manufacturers, they may have a wait-and-see attitude towards this hard drive to avoid any impact on production costs and selling prices, thereby reducing market acceptance.
Indispensable element - embedded operating system
Strictly speaking, PMP can be regarded as a multimedia version of PDA. Not only is the design architecture similar, but even from a technical level, if it is not Limited by factors such as market positioning and production costs, the audio and video playback functions possessed by PMP can be realized by PDAs. Therefore, PMP is also equipped with an embedded OS platform. In addition to the existing Windows CE .NET, BSD, Symbian/EPOC and QNX options, it can also be based on Linux.
The currently released PMP operating systems are mainly Windows CE .NET and Linux.
31》What is MP4? What are PMP and PMC?
New technology is always developing. A few years ago, the MP3 Walkman quickly occupied the market of portable music players due to its compact size and ease of use. This trend of upgrading continues to emerge in the digital market. The early MP3 Walkman replaced tapes, CDs and other products, and this kind of machine that can only listen but not watch will eventually be replaced by a new generation of portable products. Of course, this cannot be called a Walkman. Combined with video and other playback, the new generation of products can be called personal digital entertainment terminals. The representative of this type of product is the MP4 player that is currently undergoing continuous development. What are the advantages and disadvantages of MP4? Where will the future of MP4 products go? Let’s read this article to explain it to you one by one.
What is MP4?
The first thing you need to understand is, what is MP4? MP4 is the abbreviation of MPEG-4 compression format. MPEG-4 is a video format that can provide different resolutions from 320×240 to 1280×1024. Portable media players are named MP4 players because such products can support the playback of MPEG-4 format files.
What is PMC?
Most of the MP4 products on the market today are named PMP, PMC, etc. What is going on? PMC is the abbreviation of "Portable Media Center" in English, that is, "Portable Media Center". Microsoft has unified the hardware specifications of PMC. The CPU uses XScale provided by Intel, and the overall software framework is Microsoft's "Windows Portable Media Center" operating system. It seems that this time the WIN-TEL camp will enter portable media again. market, creating the standard for portable media players. The overall architecture of PMC is open, and application software can be expanded by itself based on the operating system.
What is PMP?
Like PMC, PMP is also the English abbreviation, and its English name is "Portable Media Player", which is "portable media player". Unlike PMC, PMP does not have a unified standard. In terms of application software and configuration, manufacturers can choose according to their own needs. In this way, PMP becomes more flexible and easy to expand software and so on.