H.264 video codec as a new generation of technology, and compared to traditional MPEG-2, its superior compression performance, it can achieve a higher quality low bandwidth video transmission, the video data storage take up less storage space.
Traditional DVB-T market, MPEG-2 video codec is the mainstream format. In recent years, with the bandwidth and the frequency resources become increasingly valuable, new regions of Europe, Russia, Turkey and other regional operators select H.264 as video codec formats, formed a certain scale of the market, caused STB Manufacturer’s attention. Microelectronics Co., Ltd. Shanghai Fu Han
several years ago to see this demand, introduced H.264 decoder chip FH8601. This ASIC chip DVB-T already mature STB Chips combined into a two-chip solution. FH8601 as a co-processor can receive from the main chip (such as LSI9700, NEC61123) instructions and H.264 data stream, decoding the image and then sent back to the Lord through the 601/656 display interface chip, shown by the main processing chip to do. This program has been operating to discuss Russia’s DVB-T production use.
How traditional DVB-T set-top box platform based on the realization of next-generation H.264 video decoding capabilities with a solution? Engineers to achieve this combination of two-chips which solutions need to address critical technical issues? This paper will be focused on H.264 decoder chip FH8601 platform integration with the traditional process to note the following key technical points to make elaborate:
1. Control interface and video I / O interface;
2. To achieve video and audio (A / V) synchronization;
3. Response compatibility H.264 encoded stream;
4. Mainframe system software. Control interface and video I / O Interface
As shown, in a set-top box terminals, FH8601 as a co-processor for video decoding. It provides the main chip Communicate And data transfer interface that is the most basic LocalBus interfaces. As long as the main chip can provide access to RAM or Nor Flash memory data address bus, you can achieve FH8601 control and video data transfer. The main chip how to get FH8601 decoded video data is also a systems engineer needs to be considered a problem, FH8601 aims to provide a standard ITU601/656 video output interface.
Host interface LocalBus: FH8601-chip 16-bit or 8-by-bit data width to transmit data with the host, 8-bit or 16-bit width configuration. The operation of the host of the FH8601 include reset, configuration, download firmware, write the data stream and query status.
Video data output interface: compatible ITU601/656 standard video data, the host must be able to provide the appropriate video input interface. Video output interface of the synchronous clock phase can be 0 degrees and 180 degrees phase two choices.
Audio and video synchronization Audio and video synchronization is that all the development programs of audio and video set-top box application engineers should focus on an issue. Engineers are also the technical point of spending more energy to make the system get the best audio and video effect. FH8601 realized from the program based on the actual effect, the effect of its very good audio and video synchronization.
1. MPEG audio and video simultaneously to achieve the specification guarantees
MPEG specification provides an absolute guarantee can be audio and video (A / V) synchronization of appropriate tools. Audio and video frames each have a decoder synchronization allows the sound and image reconstruction show the time stamp (PTS). The PTS value from the multiplexer in MPEG encoder to give. Before these PTS decoder receives the audio and video data, can then use these values to synchronize the playback of video and audio. In the MPEG system, due to time-division multiplexing of the bit slot, road slot, with strict time frames relations between, which is synchronized. In order to restore programs, the first decoding of the ES. Sound, image signal to reproduce the need to synchronize display, which required sending and receiving ends of the data stream to achieve synchronization.
2.FH8601 synchronization mechanism provided by
FH8601 with automatic audio and video synchronization. This feature simplifies system software complexity. Specifically, the main chip will need to FH8601 in synchronization open. In the decoding process, the main audio chip needs to be addressed to the current PTS FH8601, FH8601 for automatic synchronization of video and audio. With streaming video PTS with the write data FH8601.
Encoded stream compatibility and scalability H.264 standard as early as 2003 have been set, but after all, still in the early stages of application, such as MPEG2 encoder far as mature, so decoder encoded stream must face not the question of standards and regular upgrades . FH8601 stage in the definition of chip to consider how to deal with these issues. Way through the firmware, we have the flexibility to change those standards part of the way of software to achieve. The firmware of all the changes, does not require the participation of design engineers, but simply to replace the original firmware and download online can be.
Stream Compatibility: In addition to the current FH8601 stream through all ITU compatibility testing, but also with all major encoders docking.
Online update firmware: you need to upgrade the firmware, the only Fullhan a new firmware data file, the user directly replace the original file can be recompiled easily complete the upgrade.
System software design For DVB-T/H.264 this new solution, any one not willing to give up their resources and code software engineers will think of the accumulation of software reuse. Obviously, for those who have had DVB-T set-top box design program, the two-chip solutions for systems engineers to bring the convenience of one of the most direct, is that all the system resources can be placed directly on the new project. In the following, we also need to consider the reuse of existing software resources. In fact, the host has not changed circumstances, the original software and the code will not be any waste, unless you think that they themselves are outdated. We just need to increase under the new H.264 decoding, to transplant a small amount of drive and interface function call test.
Comparison of different options
Market Risk: From a technical point of view, the FH8601 and mature form of DVB-T chip-chip program and other support for H.264 decoding program of single-chip SoC comparison, in the R & D investment, the development cycle, program maturity has significant advantages, can greatly reduce product