Odisha CHSE +2 Vocational Audio Video Technique cheat sheet

Sound in air is a longitudinal pressure wave; speed is about 343 m/s at 20 °C, 331 m/s at 0 °C, and about 1480 m/s in water.

Frequency f (Hz) sets pitch; period T = 1/f; wavelength λ = v/f, so 100 Hz in air has λ ≈ 3.43 m.

Audible range is nominally 20 Hz–20 kHz; below is infrasound, above is ultrasound.

SPL in dB = 20 log10(p/p0), where p0 = 20 µPa; 0 dB SPL is the 1 kHz threshold of hearing and 120 dB is the pain threshold.

Doubling sound pressure raises level by 6 dB; doubling distance from a point source in a free field lowers level by 6 dB.

Harmonic content (fundamental plus integer multiples) determines timbre; amplitude determines loudness; waveform shape combines both.

Phase: identical-frequency waves in phase add constructively; 180° out of phase cancel; partial phase shift causes comb filtering.

Digital audio requires sampling above 2× bandwidth (Nyquist); 44.1 kHz captures up to 22.05 kHz, 48 kHz up to 24 kHz.

RT60 is the time for a 60 dB decay; Sabine formula RT60 = 0.161 V/A in metric units, with V in m³ and A in sabins.

Absorption coefficient α ranges from 0 (rigid reflector) to 1 (open window or perfect absorber); NRC averages α at 250, 500, 1000 and 2000 Hz.

Direct sound arrives first; reflections within about 50 ms fuse with it (Haas/precedence effect) and are perceived as timbre or loudness, not echo.

Equal-loudness contours show reduced sensitivity at low and high frequencies, especially at low SPL; hearing is most sensitive around 3–4 kHz.

Masking: a loud tone raises the threshold for nearby frequencies (frequency masking) and for sounds just before or after (temporal masking).

Binaural localisation uses interaural time difference below about 1.5 kHz and interaural level difference above about 1.5 kHz; pinna cues help elevation.

Room modes in a rigid rectangular room occur at f = (v/2)√((nx/Lx)²+(ny/Ly)²+(nz/Lz)²).

Comb filtering from a delayed copy creates peaks and notches spaced 1/τ Hz; a 1 ms delay gives 1 kHz spacing.

Prolonged exposure at 85 dBA for 8 hours is a common occupational limit; each 3 dB increase halves the permissible exposure time.

Nyquist criterion: fs > 2 fmax; an anti-alias filter precedes sampling and a reconstruction filter follows the DAC.

Bit depth n gives theoretical SNR ≈ 6.02n + 1.76 dB; 16-bit ≈ 98 dB and 24-bit ≈ 146 dB.

Standard rates: 44.1 kHz for CD, 48 kHz for video and broadcast, 96 kHz for high-resolution work; 48 kHz is the default for programme interchange with picture.

Balanced interconnect (XLR/TRS) carries hot, cold and shield; common-mode noise cancels; nominal line level is +4 dBu.

Unbalanced interconnect (RCA/TS) carries signal and shield; consumer level is −10 dBV; cable runs should be short.

Phantom power is +48 V DC on XLR pins 2 and 3; it is required by most condensers and must not be applied to passive ribbon microphones.

Dynamic range = 20 log10(max signal/noise); align programme peaks around −12 to −6 dBFS and never exceed 0 dBFS.

SMPTE timecode format is HH:MM:SS:FF; 25 fps applies in 50 Hz PAL territories and 30 fps in 60 Hz NTSC territories.

Recording media include SD, CFast, CFexpress and SSD; dual-card or dual-recorder capture provides backup for critical takes.

Dynamic microphone: moving coil, rugged, no phantom power, high SPL handling; condenser: capacitor element, high sensitivity, needs power.

Polar patterns: omni 360°, cardioid about 131° front acceptance with rear rejection, supercardioid tighter with a rear lobe, figure-8 front and rear.

Proximity effect: directional microphones boost low frequencies as source distance decreases; use a high-pass filter or greater distance.

3:1 rule: when multiple microphones pick up the same source, the distance between microphones should be at least three times the source-to-microphone distance.

Console channel strip order: input trim/gain, high-pass filter, EQ, dynamics, pan, fader, auxiliary sends and bus routing.

Nominal alignment: 0 VU corresponds to −18 dBFS or −20 dBFS; faders near unity leave headroom for peaks.

Compressor controls: threshold, ratio, attack, release and makeup gain; ratio 2:1–4:1 is gentle, while 8:1 and above approaches limiting.

Feedback control: lower gain, move the microphone away from loudspeakers, orient the cardioid null toward monitors and notch the resonant frequency.

EQ decision rule: cut narrow, boost wide; high-pass below useful content; avoid boosting frequencies already dominant in the room.

Frame rates: 24 fps for film and cinematic look, 25 fps for PAL/50 Hz, 30 fps for NTSC/60 Hz; 25p and 50i are common broadcast formats.

Progressive frames contain all lines per frame; interlaced video contains two fields, so 1080i50 has 50 fields/s and 25 frames/s.

Resolution: 1280×720 HD, 1920×1080 HD, 3840×2160 UHD 4K and 7680×4320 8K; HD and UHD are 16:9, legacy SD is 4:3.

Aspect ratio: 16:9 = 1.78:1, 4:3 = 1.33:1 and 2.39:1 widescreen; mismatched delivery requires pillarbox or letterbox.

180° shutter rule: shutter speed = 1/(2×fps); 25 fps gives 1/50 s, 50 fps gives 1/100 s and 24 fps gives 1/48 s.

Motion blur increases with longer shutter; judder appears when camera movement or frame rate is too low for the motion.

Pixel aspect ratio: HD uses square pixels; legacy SD formats used non-square pixels, so conform before editing.

Scanning: an analogue raster scans left-to-right and top-to-bottom; sync pulses define blanking and field order.

Additive mixing: red, green and blue combine to white; complementary pairs are red/cyan, green/magenta and blue/yellow.

Subtractive mixing: cyan absorbs red, magenta absorbs green and yellow absorbs blue; used in filters and print.

Analogue colour systems: NTSC 525/60, PAL 625/50 and SECAM 625/50; all separate luminance and chrominance.

Composite video combines luminance, chrominance and sync on one cable; S-Video separates Y/C; component carries Y, Pb and Pr separately.

Digital colour difference is Y′CbCr; chroma subsampling is 4:4:4 (no reduction), 4:2:2 (half horizontal chroma) and 4:2:0 (half horizontal and vertical).

Colour temperature: candle about 1800 K, tungsten 3200 K, daylight 5600 K and overcast or shade 6500–7500 K; lower Kelvin appears warmer.

Gamma encodes video for display nonlinearity; Rec.709 is HD SDR, Rec.2020 is UHD, and PQ and HLG are HDR transfer functions.

Vectorscope displays hue and saturation; waveform monitor displays luminance levels; both are used for alignment and grading.

Exposure variables are iris/f-stop, shutter speed, gain/ISO, ND filtration and available light.

f-number = focal length / entrance pupil diameter; one-stop steps 1.4, 2, 2.8, 4, 5.6, 8, 11 and 16 each halve the light.

Shutter angle formula: shutter speed = 1/(fps × 360/angle); a 180° shutter gives 1/(2×fps).

White balance presets: 3200 K tungsten and 5600 K daylight; manual balance uses a white or grey card under final lighting.

Focal length: wide angle increases field of view and depth of field; telephoto narrows view, compresses perspective and shallows depth of field.

Depth of field increases with smaller aperture, shorter focal length and greater subject distance; it decreases with a larger sensor and closer focus.

ND 0.3 cuts 1 stop, 0.6 cuts 2 stops, 0.9 cuts 3 stops and 1.2 cuts 4 stops; ND permits wide aperture in bright light.

Monitoring aids: zebras at 70–80% for skin and 100% for clipping; focus peaking for critical focus; histogram or waveform for level.

Camera movements: pan is horizontal pivot, tilt is vertical pivot, dolly/track is movement, truck is lateral, pedestal is vertical and zoom changes focal length.

Rule of thirds: place key subjects and horizon lines near the thirds intersections rather than dead centre.

Headroom leaves modest space above the head; lead room or look space is left in front of a moving or looking subject.

Shot sizes: ECU, CU, MCU, MS, MLS, LS and EWS; angle choices include high, eye-level, low and Dutch.

180-degree rule: keep the camera on one side of the action axis; 30-degree rule: change angle by at least 30° between cuts.

Three-point lighting uses key, fill and back light; key-to-fill ratio is 2:1 for soft lighting and 4:1 or higher for dramatic contrast.

Light intensity follows the inverse square law: I ∝ 1/d²; doubling distance gives one quarter intensity, a 2-stop drop.

Hard light comes from a small source and gives sharp shadows; soft light comes from a large source relative to the subject and gives gradual shadow edges.

Colour correction gels: CTB converts tungsten to daylight; CTO converts daylight to tungsten; diffusion enlarges the effective source.

Lighting ratio = (key + fill) : fill; 2:1 is flat, 4:1 is moderate and 8:1 is high contrast.

Pre-production documents: script, treatment, storyboard, shot list, shooting schedule, call sheet, budget and recce report.

AV script: two columns with video on the left and audio on the right; each row is one synchronous segment.

Screenplay format: scene heading, action, character, dialogue and parenthetical; one page is roughly one minute of screen time.

Three-act structure: setup about 25%, confrontation about 50% and resolution about 25%, with turning points at act breaks.

Shot list fields: shot number, size, angle, movement, lens, location, action, audio and notes.

Call sheet: production title, date, crew call, location, nearest hospital, contacts, weather and sunrise/sunset times.

Recce checks: power, access, noise, light, parking, toilets, permissions, safety hazards, backup routes and mobile coverage.

Clearances: talent release, location release, music sync licence, archive or footage permission and trademark clearance.

Schedule by location and lighting needs; group shots that share a setup to reduce company moves.

NLE editing workflow: ingest, proxy, assemble, trim, transitions, audio mix, grade and export; edits are frame-accurate.

Cut types: hard cut, dissolve, fade in/out and wipe; motivated transitions support story continuity.

Continuity devices: eyeline match, match cut, shot/reverse shot, cutaway, establishing shot and the 180-degree rule.

J-cut: next audio precedes picture; L-cut: previous audio trails over the next picture.

Codec versus container: H.264, HEVC and ProRes are codecs; MP4, MOV and MXF are containers holding video, audio and metadata.

Proxy workflow: edit low-resolution proxies and relink to full-resolution media before the final render.

Colour correction order: primary lift/gamma/gain, then secondary qualifiers, then creative grade; scopes guide objective decisions.

Audio post chain: dialogue edit, noise reduction, EQ, compression, ambience or music, loudness normalisation and limiter.

Delivery loudness: EBU R128 −23 LUFS, ATSC A/85 −24 LKFS; true peak is often limited to −1 dBTP.

Studio chain: source → preamp → mixer or switcher → recorder or transmitter → monitor; levels are aligned through each stage.

Multi-camera control: CCU adjusts iris and colour; vision mixer cuts between cameras; tally indicates the live camera; talkback links gallery and floor.

Floor manager relays director cues, counts down and manages talent and safety; cue lights and hand signals supplement talkback.

Field kit: charged batteries, spare media, tripod, ND filters, wind protection, headphones, cables, gaffer tape and weather cover.

Location sound: boom for reach and natural perspective; lavalier for close speech; deadcat or windshield outdoors; monitor with headphones.

Sync methods: clapperboard, timecode jam-sync, multicam audio waveform alignment and genlock for video sync.

Media offload: copy to two independent drives, verify checksums and never format a card until a verified backup exists.

Single-camera coverage: master shot, then coverage of each character and inserts; multi-camera captures continuous action from several angles.

Safety: sandbag stands, tape cables, secure overheads, check power and weather, and maintain an emergency contact list.

Digitisation: sample in time (rate) and quantise in amplitude (bit depth); Nyquist requires fs > 2 fmax.

Lossless compression preserves exact data (FLAC, ZIP); lossy compression discards perceptual redundancy (JPEG, H.264, MP3).

Codec examples: H.264/AVC, H.265/HEVC, AV1, ProRes and DNxHD; container examples: MP4, MOV, MKV and WebM.

Bitrate in Mbps = file size in megabits / duration in seconds; higher bitrate generally improves quality at the cost of bandwidth and storage.

Streaming: HLS and MPEG-DASH use segmented adaptive bitrate; CDN edge servers reduce latency and buffering.

UHD 4K is 3840×2160; HDR uses PQ or HLG with Rec.2020 wide colour gamut and higher bit depth.

Immersive media: 360° video, VR, AR and MR; spatial audio uses binaural rendering and head tracking.

IP broadcast: SMPTE ST 2110 separates essence streams; NDI carries video over IP for live production.

Platform aspect ratios: 16:9 horizontal, 9:16 vertical and 1:1 square; captions and metadata improve accessibility and search.

Project report structure: title, abstract, aims, methodology, planning, execution, results, evaluation, references and appendix.

Logbook entries record date, time, task, equipment, settings, observations and problems solved.

Viva answers justify equipment and technique choices with specifications, constraints and alternatives considered.

Practical camera check: battery, media, format, white balance, exposure, focus, audio levels, timecode and a short test recording.

Practical audio check: microphone type and pattern, phantom power, gain and level, monitoring, backup track and room tone.

Troubleshooting order: power, cable or connection, settings, source and destination; substitute known-good components.

Evidence for assessment: script, storyboard, shot list, call sheet, risk assessment, raw footage log, edit decision list and final export.

Evaluation criteria: technical quality, continuity, sound-image sync, narrative clarity, safety compliance, teamwork and documentation.

Academic integrity: cite sources, credit music and footage, obtain releases and keep original production files as evidence.