AN1482 ST Microelectronics, Inc., AN1482 Datasheet - Page 6

• Manufacturer Part Number: AN1482
• Description: Mpeg2 Main Profile Video Decoding on St100
• Manufacturer: ST Microelectronics, Inc.

AN1482 - APPLICATION NOTE
3 - PERFORMANCE OF THE DECODER
In this paragraph are presented and analyzed the performance measures of the Main Profile decoder in
a real case. The sequence considered is made of 25 frames of renata (in PAL format), coded with M=3
(distance between consecutive P images) and N=12 (distance between consecutive I images). The
encoder used to generate these test bitstreams uses recursive motion estimation. Several different
bitrates have been considered, also in order to understand the dependency of the functions from the
bitrate (Table 5).
Table 5 : Profiling of the code (Mcycles/s) for PAL format
Once measured these data, the computational cost for the different video formats is obtained
proportionally (Table 6). The bitrate indicated is referred to PAL format, and it must be scaled for the other
formats.
Table 6 : Different video formats (Mcycles/s)
Table 7 shows a summary of the code size of the different modules.
Table 7 : code size of the complete application
The total size does not include the I/O libraries (printf, fread, fwrite etc.), the functions used for dma
emulation (module dma.c), the functions used to store to file the decoded sequence (store.c) and the
startup code (crt0.o-456 bytes).
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Function
Wang IDCT
Add Prediction
Temporal prediction
Huffman dec/IQ/inv scan
Others (parsing, main)
TOTAL
PAL
2/3D1
1/2D1
CIF
Huffman decoding
Wang IDCT
Add prediction
Temporal prediction
Parsing
Headers
Others
TOTAL
Resolution
(720x576)
(544x576)
(352x576)
(352x288)
Module
Bitrate
PAL@2Mbps
2 Mbps
64.65
21.55
29.8
26.6
21.2
86.2
86.2
43.1
0.5
8.1
Code Size (Bytes)
PAL@4Mbps
34836
11136
4392
2100
5524
2336
8736
612
4 Mbps
119.8
119.8
89.85
29.95
46.5
29.5
18.2
22.1
59.9
3.5
PAL@10Mbps
10 Mbps
194.8
194.8
146.1
85.3
30.2
47.8
22.6
97.4
48.7
8.9
SLIW/GP32
Code Type
GP32
GP32
GP32
SLIW
SLIW
SLIW
SLIW
PAL@15Mbps
15 Mbps
228.4
228.4
171.3
114.2
94.8
10.4
30.2
70.4
22.6
57.1