Video and audio editing (AS Level) flashcards

Topic 11: Video and audio editing

Trim vs crop in video editing

Trimming removes time: unwanted footage from the start or end of a clip. Cropping removes the edges of the frame or image.

Subtitle vs caption

Subtitles show the spoken words. Captions show speech and other sounds, e.g. [phone rings], for deaf and hard-of-hearing viewers.

Interframe vs intraframe video compression

Interframe stores only the changes between key frames, giving much smaller files, but suffers when the whole picture changes. Intraframe compresses each frame on its own, so files are larger but quality does not depend on other frames.

Compare MP4, AVI, MOV and WMV

MP4: small for its quality and plays almost everywhere, but usually lossy. AVI: widely played on Windows but often large. MOV: Apple, high quality, suits editing, but large. WMV: Microsoft, small, weaker support elsewhere.

What does normalising audio do?

It applies the same gain to the whole clip so the loudest peak reaches a target level, which may be quieter or louder. Any DC offset should be removed first.

High pass vs low pass filter

Named after what they let through. A high pass filter keeps frequencies above the cut-off, removing rumble and hum. A low pass filter keeps frequencies below it, removing hiss.

Echo vs reverberation

Echo (delay) gives distinct, quieter repeats after a set time. Reverb is many dense reflections blended together, sounding like a room or hall.

How do you calculate the size of uncompressed audio?

Bits = sampling rate × sampling resolution × channels × seconds; ÷ 8 for bytes. E.g. 8,000 Hz × 8 bits × 1 channel × 10 s = 640,000 bits = 80,000 bytes.

File vs container

A plain file holds one stream encoded one way. A container such as MP4 or MOV wraps one or more streams plus information about them; the codec inside sets the compression.

WAV: one advantage and one disadvantage

Advantage: usually uncompressed, so full quality and best for editing. Disadvantage: very large files.