Ruankao Multimedia Application Designer (Intermediate) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Von Neumann bottleneck

The performance limit caused by sharing one bus between processor and memory. Multimedia systems bypass it with DMA, GPU blocks, and dedicated codecs that move frame data without per-pixel CPU copies.

DMA transfer

Direct Memory Access lets a device move data to or from RAM without per-instruction CPU involvement. It is essential for real-time capture of audio and video streams at high sustained rates.

Nyquist sampling theorem

A signal must be sampled at more than twice its highest frequency component to be reconstructed without aliasing. For audio, 44.1 kHz therefore captures frequencies up to 22.05 kHz.

PCM quantization SNR

For uniform b-bit pulse-code modulation, signal-to-quantization-noise ratio approximates 6.02b + 1.76 decibels. Each additional bit improves dynamic range by roughly six decibels.

Chroma subsampling 4:2:0

A YCbCr layout that keeps full luma resolution but stores chroma at one quarter of it, horizontally and vertically halved. It needs 1.5 bytes per pixel at eight-bit depth.

Run-length encoding

A lossless scheme that replaces consecutive repeated values with a count and a value. It is effective on palette images and fax data but poor on noisy natural photographs.

JPEG baseline pipeline

The still-image encoder splits into 8x8 blocks, level-shifts, applies DCT, quantizes with scaled tables, zig-zag scans, then entropy-codes DC differences and AC runs with Huffman coding.

I, P and B frames

I-frames are intra-coded independently. P-frames predict from earlier references. B-frames predict bidirectionally from past and future frames, so decoding requires reordering and extra buffering.

Psychoacoustic masking

A loud tone raises the audibility threshold for nearby quieter frequencies and times. Perceptual audio codecs discard or coarsely quantize components below this masked threshold to save bits.

GOP length trade-off

A longer group of pictures improves compression by adding more predicted frames, but increases seek latency and lets errors propagate further before the next independent I-frame resets.

RAID 5

Block-level striping with distributed parity across all disks. It tolerates one disk failure and improves read throughput, but rebuilds are slow and write performance carries parity overhead.

Sustained versus burst rate

Burst rate is a short peak transfer, while sustained rate is the continuous throughput. Real-time capture and playback succeed only when sustained rate exceeds the stream's data rate.

ADC and DAC

An analog-to-digital converter samples and quantizes incoming audio for storage or processing. A digital-to-analog converter reconstructs an analog signal for playback through speakers or headphones.

Non-destructive editing

An editing approach that references original media and stores decisions separately, so trims, effects, and color changes can be revised without rewriting or degrading the source files.

Proxy editing workflow

Editors transcode large source footage into smaller, lower-resolution proxies for smooth timeline work, then relink the originals for final rendering to preserve full output quality.

Drop-frame timecode

A timecode counting scheme that skips specific frame numbers to keep clock time aligned with 29.97 fps NTSC video, which otherwise drifts from real time over long recordings.

Alpha compositing over

The Porter-Duff over operator blends source and destination as source color times source alpha plus destination color times one minus source alpha, giving correct transparency layering.

Bicubic interpolation

A resampling method using sixteen neighboring pixels and cubic weighting. It produces smoother, sharper scaling than bilinear interpolation but can introduce slight ringing near strong edges.

Vector versus raster

Raster images store a fixed pixel grid and lose quality when enlarged. Vector graphics store geometric paths and render sharply at any resolution, suiting logos and diagrams.

Loudness normalization LUFS

Loudness Units Full Scale measures perceived loudness, not peaks. Broadcast targets around minus twenty-three LUFS and streaming around minus fourteen LUFS to even out playback levels.

3:2 pulldown

A telecine process that repeats film frames in a 3:2 pattern to convert 24 fps material to 29.97 fps NTSC. Inverse telecine detects and removes the duplicated frames.

True peak metering

A meter that reconstructs the analog waveform between samples to catch inter-sample overs. It matters because lossy encoding can push peaks above the measured sample peak.

Fitts's law

Movement time to a target equals a plus b times the base-two logarithm of twice the distance divided by target width. Bigger, closer targets are acquired faster.

Response time thresholds

About 0.1 second feels instantaneous, 1 second preserves the flow of thought, and 10 seconds is the limit before attention drifts. Longer waits need visible progress feedback.

Redundancy principle

People learn better from narration and graphics than from narration plus identical on-screen text. Duplicating spoken words as text splits attention and increases cognitive load.

HLS and MPEG-DASH

Both are HTTP-based adaptive streaming methods. HLS uses playlist files referencing media segments; DASH uses an XML manifest. Players switch renditions based on measured bandwidth.

Content-based retrieval

Searching multimedia by intrinsic features such as color histograms, texture, shape, or audio coefficients, often combined with metadata, rather than by manually entered keywords alone.

Adaptive bitrate ladder

A set of encoded renditions at increasing resolutions and bitrates, with aligned keyframes, allowing the player to switch quality mid-stream without visible artifacts or decoder resets.

Critical path method

A scheduling technique that identifies the longest chain of dependent tasks. That chain determines the shortest possible project duration and shows where delays directly slip delivery.

Creative Commons licenses

Standardized public copyright licenses combining conditions such as attribution, share-alike, non-commercial, and no-derivatives. They grant permissions in advance without individual negotiation.

Fair use four factors

A legal balancing test weighing purpose of use, nature of the work, amount used, and effect on the market. It is a defense after infringement, not automatic permission.

ISO/IEC JTC 1/SC 29

The joint standards subcommittee responsible for coding of audio, picture, multimedia, and hypermedia information, including the JPEG and MPEG families of standards.