📝 Image compression and formats (26 MCQs)

📖 Explanation: Multimedia, as outlined, combines several digital media types—text, images, audio, and video—into an integrated, interactive format. This definition captures the essence of the passage, emphasizing digital generation, storage, and transmission, whereas the other options describe only subsets or unrelated concepts.

📖 Explanation: Lossless compression guarantees that every bit of the original data can be perfectly recovered after decompression. No visual information is discarded, so the image after decompression is identical to the original, unlike lossy methods that discard details for smaller size.

📖 Explanation: Increasing the compression ratio forces the encoder to discard more high‑frequency information, which reduces the file size but introduces noticeable artifacts such as blocking or ringing. The image does not gain resolution or color accuracy; instead, quality degrades as compression becomes more aggressive.

📖 Explanation: Scientific archives often require exact replication of original data for future analysis, making lossless preservation paramount. While streaming video values low bandwidth and real‑time decoding, archival integrity outweighs those concerns, so the ability to store the image without any loss of information is the decisive factor.

📖 Explanation: When bandwidth cannot accommodate the original data rate, applying a higher compression reduces the amount of data transmitted per unit time, allowing the stream to continue without buffering. Using uncompressed video or increasing frame rate would exacerbate bandwidth demands, while adding audio channels does not address the core issue.

📖 Explanation: The DCT converts spatial pixel values into frequency coefficients, concentrating most of the signal energy into a few low‑frequency components. This energy compaction enables efficient quantization and removal of less important high‑frequency data, which is the fundamental reason JPEG adopts the DCT for effective compression.

📖 Explanation: PNG employs lossless compression that retains every pixel, resulting in larger file sizes compared to JPEG’s lossy approach, which discards perceptually less important information. Consequently, for identical dimensions and similar content, PNG files are generally larger, especially when the image contains many colors or fine detail.

📖 Explanation: QoS describes performance metrics that a network must meet to deliver multimedia smoothly, including limits on latency, sufficient bandwidth, jitter, and acceptable error rates. These guarantees ensure that audio and video arrive in time and with enough fidelity, unlike issues such as file naming or UI design.

📖 Explanation: Lossless methods keep every original bit, limiting how much data can be reduced, whereas lossy techniques sacrifice detail to reach higher ratios. Therefore, as the compression ratio increases, especially with lossy schemes, perceptual quality tends to decline because more information is discarded.

📖 Explanation: Progressive JPEG transmits the image in multiple scans, allowing a low‑resolution version to appear quickly and then be refined as more data arrives. This gives users a preview early on, whereas baseline JPEG waits until the entire file is received before rendering the full‑resolution image.

📖 Explanation: Reducing resolution lowers the total number of pixels, so fewer bits are needed to represent the same visual fidelity. Consequently, the required bitrate drops roughly in proportion to the reduction in pixel count, assuming the compression algorithm and quality settings remain constant.

📖 Explanation: H.265 (HEVC) is more efficient than H.264, delivering comparable visual quality at lower bitrates. Maintaining the same bitrate while moving to the newer codec typically yields a perceptible improvement in sharpness, reduced artifacting, and overall better image fidelity for the viewer.

📖 Explanation: Medical diagnosis often depends on subtle texture patterns that reveal tissue characteristics; losing those details can compromise diagnostic value. Therefore, a scheme that better preserves fine textures is preferred, even if color fidelity is slightly lower, because texture information is more critical for accurate interpretation.

📖 Explanation: End‑to‑end delay is the sum of latencies across all stages. Halving the compression component directly reduces the total delay by that same amount, assuming the other stages remain unchanged. This yields a proportional improvement in overall responsiveness.

📖 Explanation: When macroblocks are missing, using information from neighboring frames (temporal interpolation) can estimate the lost content based on motion continuity, often producing smoother visual results than spatial smoothing, which relies only on adjacent pixels within the same frame.

📖 Explanation: Smooth motion perception is primarily driven by frame rate; more frames per second provide finer temporal sampling, reducing motion blur. Under a fixed bandwidth, allocating bits to increase resolution sacrifices frames, which can make motion appear less fluid despite sharper images.

📖 Explanation: Adaptive streaming monitors available bandwidth and automatically selects a representation that fits within the new limit. When bandwidth falls, the client switches to a lower‑bitrate version to maintain uninterrupted playback, rather than halting or attempting higher‑quality delivery.

📖 Explanation: Quantizing high‑frequency coefficients more aggressively discards the subtle variations that define fine detail, leading to a loss of texture and crispness. The image may appear smoother or blurred, as the high‑frequency information responsible for sharp edges is reduced.

📖 Explanation: Vector graphics describe shapes using geometric equations, allowing them to be recalculated at any size without loss of detail. Raster graphics consist of fixed pixel grids; scaling them enlarges pixels, causing visible degradation. Hence, vectors are inherently resolution‑independent.

📖 Explanation: The perceived cohesion of a multimedia experience hinges on precise timing; audio cues must line up with visual events (e.g., narration matching slide transitions). Misalignment breaks immersion, whereas file naming, color depth, or bitrate have less immediate impact on the viewer’s sense of continuity.

📖 Explanation: Entropy coding (such as Huffman or arithmetic coding) follows the DCT and quantization steps to compress the resulting symbols. It assigns shorter bit patterns to symbols that occur frequently, thereby exploiting statistical redundancy and further shrinking the overall bitstream.

📖 Explanation: When packets can be reordered, the client can request retransmission of only the missing pieces without discarding subsequent packets, reducing the impact of loss. A strict in‑order protocol would have to discard all later packets until the missing one arrives, making it less tolerant.

📖 Explanation: Removing spatial redundancy cuts the data needed for each individual frame, but if consecutive frames are identical, temporal redundancy would have allowed even further savings. With only spatial reduction, the bandwidth savings are limited to the per‑frame compression, not the additional gains from frame‑to‑frame similarity.

📖 Explanation: In live broadcast environments, the delay introduced by encoding must be minimal to keep the stream synchronized with real‑time events. Even if Algo B yields slightly lower PSNR, its speed ensures timely delivery, making it the preferred choice when latency outweighs marginal quality differences.

📖 Explanation: Since capacity C is directly proportional to bandwidth B, doubling B while maintaining the same signal‑to‑noise ratio linearly doubles the theoretical maximum data rate, assuming all other factors remain unchanged.

📖 Explanation: While higher compression reduces immediate storage expense, the inability to readily access or migrate proprietary files creates significant future costs, including licensing, conversion, and potential vendor lock‑in. Therefore, interoperability and the assurance that the format will remain usable across platforms outweigh the modest storage savings.)