Digital Data Notes

Digital Files

  • File Format: Convention specifying how data is encoded in a file; critical for understanding its content. Some common formats include:

    • HTML for web pages
    • Text files (.txt)
    • Multimedia formats (ogg, mp4)
    • Image formats (png, jpeg)

  • File Extension: Series of letters indicating the file type (e.g., .jpg, .doc) which helps:

    • Identify the file type and often the program that created it.
    • Assist operating systems in launching the appropriate software to open the file.

File Compatibility

  • Platform Differences: Different computer systems use varied hardware/software leading to compatibility issues.

  • File Compatibility: Refers to how well a file can be opened across different platforms (e.g., Windows vs. Mac).

    • Important for multimedia developers to ensure that their content can be processed on various systems.

  • Program Files: Specific to certain operating systems and applications, meaning not all are compatible with one another.

    • Example: Microsoft Word may have different versions for Windows and Mac.

  • Multimedia Data Compatibility Challenges:

    1. Cross-Platform Compatibility: Different file formats (e.g., BMP vs PICT) may not work across platforms.
    2. Application Compatibility: Some formats (e.g., TIFF) work in many image editing software, enhancing usability.

Native File Formats

  • Native Formats: Specific to applications, preserving detailed data (e.g., PSD for Adobe Photoshop contains editing history and effects).
    • .doc is a native format for Word but can export to .txt or .rtf.

File Conversion

  • File Conversion: Process of changing one file type to another using software (e.g., Prism Video Converter or 'Save As' functions).

  • File Maintenance: Consists of three main steps:

    1. Identification: Clear naming and extension for files.
    2. Categorization: Grouping related files (e.g., text, images) for easy retrieval.
    3. Preservation: Creating backups and archiving files for future access.

Digitization

  • Digitization: Converting analog data (continuous) to digital format (discrete).
    • Steps:
    1. Sampling: Collecting samples from the analog signal.
    2. Quantization: Restricting values to a set number of levels.

Sampling

  • Sampling Process:

    • For sound, thousands of amplitude samples taken per second.
    • Each sample encoded in binary to represent sound.

  • Digitizing Images: Pixels represent color at different points, creating a grid.

  • Sample Rate: Refers to how often samples are taken; expressed in kilohertz for sound and pixels per inch for images.

Digital Encoding

  • Two Types of Encoding:

    • Description-Based: Each pixel's color detailed; used in bitmapped images (JPEG, TIF).
    • Command-Based: Stores instructions to recreate media (e.g., vector images EPS, AI, Adobe PDF).

  • Advantages of Command Encoding:

    • Smaller file sizes; scalable without distortion, beneficial for web applications.

File Compression

  • Compression: Re-encoding data to reduce size; crucial for efficient multimedia applications.

    • Codec: Software that compresses and decompresses files.

  • Types of Compression:

    1. Lossy Compression: Reduces bits and loses some data (e.g., MP3).
    2. Lossless Compression: Reduces size without data loss.

Digital Challenges

  • Standards: Early inconsistencies led to the adoption of common standards (ISO 9660) for CDs to enhance compatibility.

  • Bandwidth:

    • Refers to the data transfer rate; necessary for effective media streaming.
    • Improvements include DSL, T1, and satellite communications.

  • Preservation Concerns: Durability of storage media and need for periodic updates (e.g., digital tapes, CDs).

    • Migration & Emulation: Moving or replicating old formats to current technology for accessibility.