Compression and Codec Standards
For multimedia to be stored or transferred efficiently, it must be compressed. Uncompressed video is humungous - an uncompressed 10 second video digitized at 720×480 using 4:2:2 YCrCb at 30 frames per second requires 5.79 Gigabytes of storage. Compression efficiency has improved dramatically since the advent of MPEG-1 codecs used for video compact discs and the widely used video codecs today, viz. H.264, VP7 and MPEG-4 Part 2 have compression efficiency greater than 3 to 4 times the MPEG-1 codecs created in 1992.
Anatomy of a media file
A media file or stream has several different attributes that determine its performance, compatibility for a given environment and suitability in a given circumstance.
Figure 3: Anatomy of a Media File
Key attributes of a media file include:
1. Video Codec: This determines the technology used for the video that has been compressed.
2. Profiles: Specialized implementations of the video codec targeted for specific sets of applications.
3. Video Container Format: This container format determines how data is stored within the file, including the compression technology used and meta-data supported.
4. Hardware vs. Software Implementation: Codecs can be implemented in either hardware or software. While a hardware implementation is more power efficient, it requires an additional hardware processor, or FPGA, in the device and does not provide a product manager with the greater flexibility of a software codec.
5. Platform-specific Optimizations: Several hardware platforms have special characteristics and provide a customized set of instructions, which if used correctly, can greatly increase the efficiency of codecs. Codecs that are customized to specific platforms can prove to be more efficient due to greater optimization enabled by use of the platforms’ inherent characteristics.
6. Niche uses: Some codecs have compression algorithms that are better suited to specific applications (e.g., VP7 codec for animated content).
NEXT: Differences in Video Compression Technologies
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