Multimedia Production
AdvancedMultimedia weaves text, graphics, audio, animation and video together. Bitmaps are built from pixels, with resolution and colour depth deciding file size; vector graphics are described mathematically and scale without distortion. Compression is lossless or lossy; animation plays frame by frame and streaming plays while downloading. Production runs planning, production, testing and publishing.
- Multimedia weaves text, graphics, audio, animation and video; always balance effect against file size
- Uncompressed image size = width × height pixels × bytes per pixel (colour depth ÷ 8)
- Vector graphics scale without distortion for logos; bitmaps suit photos but grow jagged when enlarged
文體小知識：科技知識說明文——講解多媒體元素的數碼化原理、影像檔案大小的計算、壓縮與格式的選擇，以及製作流程，是選修單元「多媒體製作」的入門知識。
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1Multimedia combines two or more media elements — commonly text, graphics, audio, animation and video — presented with interaction, and is widely used in teaching presentations, web pages, promotional clips and games. Compared with plain text, multimedia appeals to both sight and hearing and delivers information more vividly; but the more elements a work carries, the larger its file, so production always balances quality against file size.
2Computer graphics come in two families. A bitmap is built from pixels, each recording a colour; resolution is the number of pixels, such as 1024×768, and colour depth is how many bits record each pixel's colour — together they determine the uncompressed file size. Vector graphics describe points, lines and shapes mathematically: files are small and enlarging never blurs them, which suits logos and illustrations, while continuous-tone photographs suit bitmaps.
3For audio, sound becomes digital through sampling: the more samples per second and the finer each measurement, the better the quality and the bigger the file. Video is a sequence of frames played in quick succession. For example, an animation at 30 frames per second needs 1800 frames for one minute — video files are enormous, which is why compression is essential.
4Compression comes in two kinds. Lossless compression restores the original data exactly, suiting text, programs and images whose details must survive; lossy compression discards data the eye or ear hardly notices in exchange for a far smaller file — photographs are commonly stored as JPEG, music as MP3 and video as MPEG. Choose formats by purpose: images needing transparency or repeated editing favour lossless formats, while photos shown online can trade some quality for loading speed.
5Streaming lets multimedia play on the Internet while it downloads, so users need not wait for the whole file — the reason video platforms flourish. Producing a multimedia work follows stages: plan the content and storyboard first, then produce and integrate the elements, test playback on different devices, and finally publish in a suitable format and resolution. Step by step is how quality is guaranteed.
1Summary 重點摘要
Multimedia weaves text, graphics, audio, animation and video together. Bitmaps are built from pixels, with resolution and colour depth deciding file size; vector graphics are described mathematically and scale without distortion. Compression is lossless or lossy; animation plays frame by frame and streaming plays while downloading. Production runs planning, production, testing and publishing.
2Vocabulary cards Vocabulary
The combined use of text, graphics, audio, animation and video in one work.
The smallest unit of a bitmap image, recording the colour of one point.
The number of pixels in an image, e.g. 1024×768; higher resolution gives finer detail and larger files.
The number of bits used to store each pixel's colour; 24 bits allow about 16.7 million colours.
An image described as a grid of pixels; it becomes jagged when enlarged and suits photographs.
Graphics described mathematically as points, lines and shapes; they scale without quality loss and suit logos.
Encoding techniques that reduce file size, in lossless and lossy forms.
Compression that restores the original data exactly, suitable for text and detail-critical images.
Compression that discards less noticeable data to shrink files greatly; it cannot be reversed, as in JPEG.
A technique that plays audio or video while it downloads, so users need not wait for the whole file.
3Step by step Steps
- Step 1: Multimedia elements and applicationsMultimedia weaves text, graphics, audio, animation and video into interactive presentations. For example, an open-day presentation may show campus photos and a promotional clip, with background music and clickable buttons, letting visitors choose what interests them — far more engaging than a one-way text leaflet. Teaching software, web pages, news reports and games are all multimedia; more elements mean more expressive power but larger files, so production always weighs effect against size.
- Step 2: Pixels, resolution and colour depthBitmaps are assembled from pixels, and their fineness depends on resolution and colour depth. For example, a 1024×768 image has 786432 pixels; at 24-bit colour depth each pixel takes 3 bytes, so the uncompressed size is about 2.25 MB. Higher resolution means sharper images and higher colour depth means richer colours, but both enlarge the file. Images for printing need higher resolution than those shown on screens, otherwise pixels become visible as rough blocks when enlarged.
- Step 3: Choosing between bitmap and vectorBitmaps record colour pixel by pixel and excel at continuous-tone photographs; vector graphics describe points, lines, shapes and fills mathematically, producing small files that stay sharp at any magnification. For example, a school badge printed on certificates, flags and giant banners should be drawn as a vector, staying crisp however it is enlarged; a bitmap would show jagged edges. As a rule, logos, icons and illustrations suit vectors, while photos and screenshots suit bitmaps.
- Step 4: Digitising sound and animationSound is digitised by sampling: measuring the wave at very short intervals; more samples per second and finer measurements give better fidelity and more data. Animation and video are strings of frames played in succession. For example, a two-minute clip at 30 frames per second holds 3600 frames; if each frame is a fairly high-resolution image, the uncompressed file runs to gigabytes — showing how enormous audiovisual data is, and why compression and streaming are standard practice.
- Step 5: Compression and format choicesCompression splits into two families. Lossless encoding records the original data in fewer bits and restores it exactly, fitting text files, programs and images edited repeatedly; lossy compression discards what eyes or ears hardly notice, achieving much higher ratios but never reversible. For example, a 2.25 MB photo saved as JPEG may shrink to a few hundred KB while still looking sharp; but repeated saving degrades quality each time. As for formats, JPEG suits photos, PNG is lossless with transparency support, and MP3 and MPEG serve music and video.
- Step 6: Streaming and online playbackAudiovisual files often run to hundreds of megabytes; waiting for a full download before playing is unacceptable. Streaming chops the file into small segments that play while the rest downloads, with playback staying slightly ahead. For example, when you press play on a video platform and the show starts within seconds, that is streaming; when the network slows, quality drops automatically as the system trims the transfer to keep playback smooth. Streaming has made educational videos and live broadcasts part of everyday life.
- Step 7: The multimedia production stagesProducing multimedia follows stages rather than improvising. Plan: define the audience and purpose, design the storyboard and script, list the elements needed. Produce: shoot, draw and record, then integrate with software. Test: play on different devices and browsers, checking links, volume and loading speed. Publish: pick the format and resolution by purpose. For example, a presentation tested only on the teacher's laptop may show tiny text or stuttering video on the hall's big screen — testing before publishing is never optional.
5Worked example Example
Calculation and selection task: the open-day team must prepare a digital poster and a short promotional video. The poster uses a photo of 1600×1200 pixels at 24-bit colour depth; the video runs 60 seconds at 25 frames per second. Calculate the uncompressed size of the photo, and state, with reasons, the format and compression for the poster and the video.
- First count the pixels: 1600×1200 = 1920000 pixels — the basis of every file-size calculation
- Then convert bits to bytes: 24-bit colour depth means 3 bytes per pixel (24 ÷ 8), so the total is 1920000 × 3 = 5760000 bytes
- Convert the unit: 5760000 ÷ 1024 ÷ 1024 ≈ 5.49 MB uncompressed; for print the poster keeps full resolution, in PNG (lossless) or high-quality JPEG
- For the video: 60 s × 25 frames per second = 1500 frames; video must use lossy compression such as MPEG, or the file would be far too large to play and share
- Set out every step and justify each format choice: lossless keeps detail, lossy buys a small file
- Answer: The uncompressed photo size = 1600 × 1200 pixels × 3 bytes per pixel = 5760000 bytes, i.e. 5760000 ÷ 1024 ÷ 1024 ≈ 5.49 MB. The poster will be printed large, so keep high resolution in a lossless format such as PNG; if it only goes on the school website, a high-quality lossy JPEG shrinks the file. The video has 60 × 25 = 1500 frames; uncompressed it would reach several gigabytes, so MPEG-style lossy compression is essential, shrinking the file dramatically at acceptable quality for smooth playback and sharing. The marking points: total pixels, bytes per pixel, unit conversion and the reason for each format — all four required.
6Common mistakes Mistakes
7Quick check Quick check
Q1How large is an uncompressed 1024×768 image at 24-bit colour depth?
Q2How do vector graphics differ from bitmaps, and what suits each?
Q3What is the main difference between lossless and lossy compression?
Q4A video runs at 25 frames per second for 2 minutes — how many frames?
Q5How does streaming improve online viewing?
8Recap Recap
- Multimedia weaves text, graphics, audio, animation and video; always balance effect against file size
- Uncompressed image size = width × height pixels × bytes per pixel (colour depth ÷ 8)
- Vector graphics scale without distortion for logos; bitmaps suit photos but grow jagged when enlarged
- Lossless compression restores everything; lossy trades quality for size — JPEG, MP3 and MPEG each have their place
- Streaming plays while downloading; production runs plan, produce, test, publish