03-11-2012, 05:03 PM
HDD EMBEDDED DSR
[attachment=38119]
INTRODUCTION
As the digital satellite broadcasting is developing, the needs for efficient management of various multimedia dates have been increased. The increase in the number channel makes it difficult to select channel that they want. Efficient digital data storage and management are the indispensable as the demand for multimedia increases. This paper presents a system, which embeds the HDD to record the broadcasting data and play them back whenever the user wants.
Nowadays, efficient storage and management of enormous broadcasting data are necessary, as the digital broadcasting is getting popular rapidly. According to the current situation, the international standards such as MPEG (moving picture experts group) –2, MPEG-3, and MPEG-7, have established efficient data storage and transmission. The standards such as DVB (digital data broadcasting) and ATSC (Advanced Television Committee) are established in order to apply these standards to the real broadcasting system. The characteristic of the digital broadcasting is multi-program emission through only one single physical channel so that the number of logical channels will be much more than that of analog TV channels. It is not easy to find the beloved program among a large number of programs because the number logical channels increases in geometric progress as the broadcasting environment changes from analog to digital. Therefore, the probabilities that the program the user wants can be broadcasted at the same time are increased.
SYSTEM OVERVIEW
This system contains the HDD interface for data transmission in addition to the basic DSR. Figure 2.1 shows the block diagram of the HDD embedded DSR. The received data from the satellite is demodulated and changed into the digital signal. Then it goes through the NIM (Network Interface Module) block. These digital signals contain multiple programs that are mixed into one transport stream. The single program that is selected by the user is filtered at the DEMUX (Demultiplexer) part and sent to the DSR inner buffer. If the user wants to record the program, the data in the buffer will be stored in the HDD, otherwise the data will be directly sent to the MPEG decoders to decompress. When the user wants to play the recorded program, the data is read from the HDD and sent to the MPEG decoders. The MPEG decoders decompress the MPEG PES (Packetized Elementary Stream), and then send them to the TV screen and the speakers through the video encoder and the PCM (Pulse Code Modulation) respectively.
DIGITAL VIDEO RECORDER
Here developed DVR (Digital Video Recorder) functions, i.e., record play random access trick mode play to give users conventional VCR options.
A/V Stream Save
The audio and video streams coming from the DEMUX are stored in the pre-buffer in the form of 184 bytes PES that excludes the 4 byte header information from 188 bytes TS (Transport stream). The stored size in the buffer can be less than 184 bytes as per PES contents. The buffers are needed because the HDD needs more access time than RAM. The audio and video streams in the pre-buffer are transferred to the HDD when the packet buffer level is larger than the size of the HDD writing unit, and then we can start storing additional header information along with the audio and video stream in the HDD. As the audio and video streams should be saved at the same time, it is necessary to separate buffering task and writing task for the real time processing. The GOP (Group of pictures) header location is also saved separately for random access and trick mode play.
A/V Play
For the play back, the audio and video streams saved on the HDD are read and classified using header information, and are transferred to the bit-buffers using the DMA (Direct Memory Access) respectively. The streams in the bit-buffer are decoded and played by the audio and video drivers. The basic idea of the architecture is to build flow control to avoid underflow and overflow by controlling delay time. Bit-buffer level should be checked before reading the audio and video streams from the HDD. To avoid overflow, few delay times are given to the tasks, if the buffer level is greater than the threshold. Here, we have assumed that underflow does not occur because the HDD access speed is much faster than the bit rate of the streams. While playing a saved file, for the ‘pause’ and ‘resume’ like a conventional VCR, we stop the task and restart it again respectively.
Random Access and Forward/Backward Skip Play
Instead of playing the whole file consecutively for a long time, user wants to play specific random position where the users want to play using the random access ability of the HDD, which is the most distinguishable ability as compared to tape recorders. If users select the play position, the nearest GOP (Group of Pictures) header position is found at that point. The audio and video data are read at the GOP header position and transmitted to the decoder. The decoder searches a nearest intra-picture header and plays it at that point. Skip play is also done by moving the playing position forward and backward from the current position
Trick Mode Play
To implement trick mode play such as fast-forward, fast -backward and slow play, packs that include intra-pictures, are marked and saved in the table. Controlling decoder’s flow and using the characteristics of the MPEG video can implement fast and slow play. The decoder flow control method is as follows. For the normal speed play, the decoder decodes the frame at every vertical sync interrupt and wait until the next interrupt. For the fast play, this wait is removed and next interrupt is made instantly and then the decoding process speed is increased. For the slow play, if this interrupt accumulates up to the fixed time, the picture is decoded. The other method using the characteristics of MPEG video is that only marked packs are read from a disk and delivered to the decoder. The frames to skip decoding depend on the picture type. Fast play, less than 12 times speed, uses skipping method. Fast backward play can be implemented by searching the GOP header position in the reverse order, and then only intra-picture is decoded. To play all frames, memory is needed to store more than12-decoded frames.
FILE MANAGEMENT OF HDD
We design and implement the file system for efficient management of the saved data. This file system offers direct file access service to the application program.
As an HDD device is primarily designed to record burst data, it is suited for audio and video signals and other continuous data. So there are few problem associated with recording of high bit rate audio and video signals on a conventional file system designed for storing the computer data. To increase the disk access efficiency, a disk should be accessed at the optimal size that minimizes the rate of the overhead, such as head-seek time and latency of the occupation time. We designed efficient file management system, which is called ‘Simplified FAT Method’, when we store audio and video streams. We read and write 8 sectors at one time. Audio and video have there own header information per writing unit. One cluster consists of multiple of HDD writing units. File system finds the nearest cluster from the current writing cluster. By using the proposed file system, file copy, delete, move and directory management operations are also possible. There are three parts in the file system: disk management, file management and directory management. For the disk management, we have to design logical format of disk like PT (Partition table), BR (Boot Record), FAT (File Allocation Table) and directory entry.
[attachment=38119]
INTRODUCTION
As the digital satellite broadcasting is developing, the needs for efficient management of various multimedia dates have been increased. The increase in the number channel makes it difficult to select channel that they want. Efficient digital data storage and management are the indispensable as the demand for multimedia increases. This paper presents a system, which embeds the HDD to record the broadcasting data and play them back whenever the user wants.
Nowadays, efficient storage and management of enormous broadcasting data are necessary, as the digital broadcasting is getting popular rapidly. According to the current situation, the international standards such as MPEG (moving picture experts group) –2, MPEG-3, and MPEG-7, have established efficient data storage and transmission. The standards such as DVB (digital data broadcasting) and ATSC (Advanced Television Committee) are established in order to apply these standards to the real broadcasting system. The characteristic of the digital broadcasting is multi-program emission through only one single physical channel so that the number of logical channels will be much more than that of analog TV channels. It is not easy to find the beloved program among a large number of programs because the number logical channels increases in geometric progress as the broadcasting environment changes from analog to digital. Therefore, the probabilities that the program the user wants can be broadcasted at the same time are increased.
SYSTEM OVERVIEW
This system contains the HDD interface for data transmission in addition to the basic DSR. Figure 2.1 shows the block diagram of the HDD embedded DSR. The received data from the satellite is demodulated and changed into the digital signal. Then it goes through the NIM (Network Interface Module) block. These digital signals contain multiple programs that are mixed into one transport stream. The single program that is selected by the user is filtered at the DEMUX (Demultiplexer) part and sent to the DSR inner buffer. If the user wants to record the program, the data in the buffer will be stored in the HDD, otherwise the data will be directly sent to the MPEG decoders to decompress. When the user wants to play the recorded program, the data is read from the HDD and sent to the MPEG decoders. The MPEG decoders decompress the MPEG PES (Packetized Elementary Stream), and then send them to the TV screen and the speakers through the video encoder and the PCM (Pulse Code Modulation) respectively.
DIGITAL VIDEO RECORDER
Here developed DVR (Digital Video Recorder) functions, i.e., record play random access trick mode play to give users conventional VCR options.
A/V Stream Save
The audio and video streams coming from the DEMUX are stored in the pre-buffer in the form of 184 bytes PES that excludes the 4 byte header information from 188 bytes TS (Transport stream). The stored size in the buffer can be less than 184 bytes as per PES contents. The buffers are needed because the HDD needs more access time than RAM. The audio and video streams in the pre-buffer are transferred to the HDD when the packet buffer level is larger than the size of the HDD writing unit, and then we can start storing additional header information along with the audio and video stream in the HDD. As the audio and video streams should be saved at the same time, it is necessary to separate buffering task and writing task for the real time processing. The GOP (Group of pictures) header location is also saved separately for random access and trick mode play.
A/V Play
For the play back, the audio and video streams saved on the HDD are read and classified using header information, and are transferred to the bit-buffers using the DMA (Direct Memory Access) respectively. The streams in the bit-buffer are decoded and played by the audio and video drivers. The basic idea of the architecture is to build flow control to avoid underflow and overflow by controlling delay time. Bit-buffer level should be checked before reading the audio and video streams from the HDD. To avoid overflow, few delay times are given to the tasks, if the buffer level is greater than the threshold. Here, we have assumed that underflow does not occur because the HDD access speed is much faster than the bit rate of the streams. While playing a saved file, for the ‘pause’ and ‘resume’ like a conventional VCR, we stop the task and restart it again respectively.
Random Access and Forward/Backward Skip Play
Instead of playing the whole file consecutively for a long time, user wants to play specific random position where the users want to play using the random access ability of the HDD, which is the most distinguishable ability as compared to tape recorders. If users select the play position, the nearest GOP (Group of Pictures) header position is found at that point. The audio and video data are read at the GOP header position and transmitted to the decoder. The decoder searches a nearest intra-picture header and plays it at that point. Skip play is also done by moving the playing position forward and backward from the current position
Trick Mode Play
To implement trick mode play such as fast-forward, fast -backward and slow play, packs that include intra-pictures, are marked and saved in the table. Controlling decoder’s flow and using the characteristics of the MPEG video can implement fast and slow play. The decoder flow control method is as follows. For the normal speed play, the decoder decodes the frame at every vertical sync interrupt and wait until the next interrupt. For the fast play, this wait is removed and next interrupt is made instantly and then the decoding process speed is increased. For the slow play, if this interrupt accumulates up to the fixed time, the picture is decoded. The other method using the characteristics of MPEG video is that only marked packs are read from a disk and delivered to the decoder. The frames to skip decoding depend on the picture type. Fast play, less than 12 times speed, uses skipping method. Fast backward play can be implemented by searching the GOP header position in the reverse order, and then only intra-picture is decoded. To play all frames, memory is needed to store more than12-decoded frames.
FILE MANAGEMENT OF HDD
We design and implement the file system for efficient management of the saved data. This file system offers direct file access service to the application program.
As an HDD device is primarily designed to record burst data, it is suited for audio and video signals and other continuous data. So there are few problem associated with recording of high bit rate audio and video signals on a conventional file system designed for storing the computer data. To increase the disk access efficiency, a disk should be accessed at the optimal size that minimizes the rate of the overhead, such as head-seek time and latency of the occupation time. We designed efficient file management system, which is called ‘Simplified FAT Method’, when we store audio and video streams. We read and write 8 sectors at one time. Audio and video have there own header information per writing unit. One cluster consists of multiple of HDD writing units. File system finds the nearest cluster from the current writing cluster. By using the proposed file system, file copy, delete, move and directory management operations are also possible. There are three parts in the file system: disk management, file management and directory management. For the disk management, we have to design logical format of disk like PT (Partition table), BR (Boot Record), FAT (File Allocation Table) and directory entry.