MNEMEE - Electronic Systems - Technische Universiteit Eindhoven

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5. Abstract Embedded software applications use statically and dynamically allocated data objects for which storage space must be allocated. This allocation should take the access pattern to these data objects into account in order to minimize the required storage space. This deliverable presents several techniques to analyze the access behaviour to statically and dynamically allocated data objects. The aim of these analysis techniques is to identify the different scenarios of data usage and to highlight optimization opportunities for WP2 and WP3. The deliverable also presents a strategy to model the application with the identified scenarios in a dataflow graph. This dataflow model can be used to map an application onto a multi-processor platform while providing timing guarantees and minimizing the resource usage of the application within each scenario. Public Page 8 of 87
6. Introduction Multimedia applications constitute a huge application space for embedded systems. They underlie many common entertainment devices, for example, cell phones, digital set-top boxes and digital cameras. Most of these devices deal with the processing of audio and video streams. This processing is done by applications that perform functions like object recognition, object detection and image enhancement on the streams. Typically, these streams are compressed before they are transmitted from the place where they are recorded (sender) to the place where they are played-back (receiver). Applications that compress and decompress audio and video streams are therefore among the most dominant streaming multimedia applications [51]. The compression of an audio or video stream is performed by an encoder. This encoder tries to pack the relevant data in the stream into as few bits as possible. The amount of bits that need to be transmitted per second between the sender and receiver is called the bit-rate. To reduce the bit-rate, audio and video encoders usually use a lossy encoding scheme. In such an encoding scheme, the encoder removes those details from the stream that have the smallest impact on the perceived quality of the stream by the user. Typically, encoders allow a tradeoff between the perceived quality and the bit-rate of a stream. The receiver of the stream must use a decoder to reconstruct the received audio or video stream. After decoding, the stream can be output to the user, or additional processing can be performed on it to improve its quality (e.g., noise filtering), or information can be extracted from it (e.g., object detection). There exist a number of different audio and video compression standards that are used in many embedded multimedia devices. Popular video coding standards are H.263 [36] (e.g., used for video conferencing) and MPEG-2 [34] (e.g., used for DVD) and their successors H.264 and MPEG-4 [35][37]. Audio streams are often compressed using the MPEG-1 Layer 3 (MP3) standard [32] or the Ogg Vorbis standard [38]. Figure 1 – An interactive 3D game with streaming video based mode [25]. Public Page 9 of 87
Page 1 and 2: Information Societies Technology (I
Page 3 and 4: 9.5. METRICS AND COST FACTORS FOR D
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Page 7: 4. Preface The main objectives of t
Page 11 and 12: Figure 2 - Preliminary MNEMEE sourc
Page 13 and 14: modelled with an FSM-based SADF, on
Page 15 and 16: analyzing the basic operations of t
Page 17 and 18: Figure 5 - SDFG-based MP-SoC design
Page 19 and 20: Figure 6 - H.263 encoder mapped ont
Page 21 and 22: transitions reflect possible next s
Page 23 and 24: parameters is modified, the applica
Page 25 and 26: There is however one problem with u
Page 27 and 28: 7.6. FSM-based SADF-based multi-pro
Page 29 and 30: 8. Statically allocated data storag
Page 31 and 32: Embedded systems differ from genera
Page 33 and 34: Plasma), etc., is enabled by compre
Page 35 and 36: One of the most important developme
Page 37 and 38: The Atomium/Analysis version includ
Page 39 and 40: 8.4.3. Profiling steps Profiling th
Page 41 and 42: Array size [bytes] Number of access
Page 43 and 44: For multimedia application this is
Page 45 and 46: Figure 22 - Data re-use at differen
Page 47 and 48: Figure 24 - (Pruned) re-use graph o
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Page 51 and 52: has to be refreshed completely, bec
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combination of DDT implementations.
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manager does not know beforehand wh
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locked remains allocated and the DM
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Improving the performance of the DM
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The problem with the aforementioned
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1. Problem 1: Increased complexity
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Table 3 - Comparison of different p
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Table 4 - Profiling information sto
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Figure 40 - Maximum number of objec
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Figure 43 - Utilization of the allo
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10. Conclusions Future multimedia a
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[17] Ang, S., Constantinides, G., L
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[34] MPEG-2. Generic coding of movi
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[65] SGI. Standard template library
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12. Glossary ANL Atomium analysis D
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