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參數(shù)資料
| 型號： | TMS320AV220 |
| 廠商： | Texas Instruments, Inc. |
| 英文描述： | Video CD MPEG Decoder(視頻CD MPEG編碼器) |
| 中文描述： | 視頻CD MPEG解碼器（視頻光盤的MPEG編碼器） |
| 文件頁數(shù)： | 15/31頁 |
| 文件大?。?/td> | 612K |
| 代理商： | TMS320AV220 |
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TMS320AV220
VIDEO CD MPEG DECODER
SCSS016A – JUNE 1994 – REVISED JANUARY 1996
15
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
error handling
The CDERROR input signals an error in the compressed-data input stream. If the error is in the video portion
of the input stream, the ’AV220 handles the error by either blanking or repeating the frame. If the error is in an
audio frame, the ’AV220 instructs the TMS320AV120 to mute the offending frame. This is accomplished by
sending a zero value PTS to the ‘AV120.
video data (GOPs), audio-frame data, and audio bypass
The ’AV220 decodes full MPEG-1 system streams (pack layer) and MPEG-1 packet streams. In order to decode
non-packetized data [i.e., a video sequence (group of pictures, GOPs) or for the ’AV220 to pass audio-frame
data or PCM data to the ’AV120], a packet header must precede the data. The packet headers for video and
audio data, respectively, are 00 00 01 E0 XX XX FF 0F [data] and 00 00 01 C0 XX XX FF 0F [data], where
XX XX is the data length plus two bytes and [data] is the video or audio data. Since the data length is represented
by two bytes a header needs to precede at most every 64K minus two bytes of data. For reference, related
MPEG-1 start codes are listed in the following table.
HEADER TYPE
START CODES (HEX)
Pack
00 00 01 BA
Video packets
00 00 01 E0 thru 00 00 01 EF
Audio packets
00 00 01 C0 thru 00 00 01 DF
Video sequence (GOPs)
00 00 01 B3
MPEG decoding with the ’AV220/’AV120
Implementation of a decoding engine with the ’AV220/’AV120 is a fairly straight-forward process, but a few points
must be noted. In most consumer applications, such as video CD or Karaoke playback systems, a CD-ROM
decoder receives MPEG-system data from the CD-ROM transport mechanism and forwards the data onto the
’AV220. The popular Sanyo and Sony CD-ROM decoders contain a FIFO buffer to allow for ’AV220 rate
variations. In applications such as these, the receive rate is approximately constant at or about 1.2 Mbit/s to
1.5 Mbit/s. The ’AV220 does not accept data at an exact constant rate. The receive-data rate is slowed slightly
when processing system or packet headers. These small rate variations are handled by the logic upstream of
the ’AV220.
In other applications such as computer systems, a CD-ROM decoder is not necessarily used. CD data is usually
read by a system mechanism and data is stored in the main computer memory. MPEG data is then transferred
to the ’AV220 decoder under the main CPU or DMA control. In these circumstances, the MPEG data rate is not
constant but rather of a bursty nature. One problem with bursty data is that it potentially could fill the ’AV220
internal buffers. When this occurs, data is only accepted as space becomes available. If the ’AV220 buffers are
filled while receiving audio MPEG data, delays may take up to 30 ms for subsequent bytes; if the receiving data
is video MPEG data, delays may take from tens to several hundred ms. These delays are short term and depend
on the MPEG data and the requirements of the stream-decoding mechanism. These variations can be ignored
if the SONY (on-demand) transfer mechanism is used, but if the SANYO mechanism is used, the system must
ensure that these internal buffers are not overfilled or make provision for these long delays. If the SANYO mode
is used in computer systems, it is recommended that the psuedo-DMA method be used (see DMA_MODE
register for details about this mechanism).
Another problem with bursty environments is correlation of audio and video time stamps with the MPEG data
display. The default values of the ’AV220 work well for most applications, but in some environments modification
of the MPEG-stream time stamp handling may be required (see SYNC_CTL register for details about time stamp
control).
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相關代理商/技術參數(shù) |
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| TMS320AV220PCM | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Audio/Video Decoder for MPEG |
| TMS320AV410 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Color Encoder Circuit |
| TMS320AV410PJM | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| TMS320AV411 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Color Encoder Circuit |
| TMS320AV411PJM | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Texas Instruments 功能描述: |
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