Sound Formats Quick Reference Sound in Film
Theatrical Sound Formats
| Format | Years Active | Channels | Medium | Notes |
|---|---|---|---|---|
| Optical mono | 1930s-present (as fallback) | 1.0 | Photographic track on 35mm print | Default for standard exhibition through mid-1970s |
| CinemaScope magnetic | 1953-~1960 | 4.0 (L/C/R/S) | Magnetic stripes on 35mm print | Cost killed it by early 1960s |
| Todd-AO / 70mm magnetic | 1955-~1992 | 6.0 (5 screen + 1 surround) | Magnetic stripes on 70mm print | Roadshow prestige format; best analog theatrical sound |
| Dolby Stereo | 1976-~1999 | 4.0 matrix (L/C/R/S) | Encoded in optical stereo track on 35mm print | Backwards-compatible; dominated 1977-1992 |
| Dolby SR | 1986-~1999 | 4.0 matrix (improved NR) | Same as Dolby Stereo with better noise reduction | Incremental improvement over Dolby Stereo |
| Dolby Digital (AC-3) | 1992-present | 5.1 | Data blocks between sprocket holes on 35mm | First discrete digital theatrical format |
| DTS | 1993-present | 5.1 | Timecode on print, audio on separate CD-ROM | Higher bitrate than Dolby Digital |
| SDDS | 1993-~2002 | 7.1 (up to 8 channels) | Data on outer edges of 35mm print | Sony format; never caught on |
| Dolby Digital Surround EX | 1999-~2010 | 6.1 matrix | Added rear center via matrix | Debuted with Star Wars: Episode I |
| Dolby Atmos | 2012-present | Object-based (128 objects + 7.1.4 bed) | Digital cinema package | Current standard for premium theatrical |
| DTS:X | 2015-present | Object-based | Digital cinema package | Atmos competitor; less theatrical adoption |
Home Physical Media Audio Formats
| Format | Home Medium | Channels | Codec Type | Bitrate | Notes |
|---|---|---|---|---|---|
| VHS linear mono | VHS | 1.0 | Analog | — | ~42 dB SNR, ~10 kHz bandwidth |
| VHS Hi-Fi | VHS | 2.0 | Analog FM | — | ~70 dB SNR, 20 kHz bandwidth |
| Laserdisc analog stereo | Laserdisc | 2.0 | Analog FM | — | Hi-fi quality; Dolby Surround decodable |
| Laserdisc PCM digital | Laserdisc | 2.0 | PCM (uncompressed) | ~1.4 Mbps | 16-bit/44.1 kHz; CD quality |
| Laserdisc AC-3 | Laserdisc | 5.1 | Dolby Digital (lossy) | 384 kbps | Required external RF demodulator |
| Laserdisc DTS | Laserdisc | 5.1 | DTS (lossy) | ~1.5 Mbps | Via digital output; higher bitrate than AC-3 |
| DVD Dolby Digital | DVD | Up to 5.1 | AC-3 (lossy) | 192-448 kbps | Mandatory codec for NTSC DVDs |
| DVD DTS | DVD | Up to 6.1 | DTS (lossy) | 768-1509 kbps | Optional; higher bitrate |
| DVD PCM | DVD | Up to 5.1 (rarely) | Uncompressed | Up to 6.1 Mbps | Usually 2.0 only due to space constraints |
| Blu-ray Dolby TrueHD | Blu-ray | Up to 7.1 | MLP (lossless) | 1.5-18 Mbps | Bit-for-bit identical to studio master |
| Blu-ray DTS-HD MA | Blu-ray | Up to 7.1 | Lossless | Up to 24.5 Mbps | Equivalent to Dolby TrueHD in fidelity |
| Blu-ray PCM | Blu-ray | Up to 7.1 | Uncompressed | Up to 27.6 Mbps | No compression at all; rare due to size |
| UHD Dolby Atmos | UHD Blu-ray | Object-based (up to 7.1.4+ bed) | TrueHD + Atmos metadata | Variable | Falls back to TrueHD 7.1 without Atmos hardware |
| UHD DTS:X | UHD Blu-ray | Object-based | DTS-HD MA + DTS:X metadata | Variable | Falls back to DTS-HD MA without DTS:X hardware |
Speaker Configuration Shorthand
| Notation | Meaning | Speakers |
|---|---|---|
| 1.0 | Mono | 1 center |
| 2.0 | Stereo | Left, Right |
| 4.0 | Quad / Dolby Stereo matrix | Left, Center, Right, Surround |
| 5.1 | Standard surround | L, C, R, Left Surround, Right Surround, LFE (subwoofer) |
| 6.1 | Surround EX / DTS-ES | 5.1 + rear center |
| 7.1 | Extended surround | L, C, R, LS, RS, Left Back, Right Back, LFE |
| 5.1.2 | Atmos (basic) | 5.1 + 2 height channels |
| 5.1.4 | Atmos (mid-range) | 5.1 + 4 height channels |
| 7.1.4 | Atmos (reference) | 7.1 + 4 height channels |
| 7.1.6 | Atmos (high-end) | 7.1 + 6 height channels |
| 9.1.6 | Atmos (maximum home) | 9.1 + 6 height channels |
Quick Glossary
- Lossy: Compression that discards data deemed inaudible. Dolby Digital (AC-3), DTS core. Smaller files, imperceptible-to-minor quality loss.
- Lossless: Compression that reduces file size but decodes to identical output. Dolby TrueHD, DTS-HD Master Audio. No quality loss.
- PCM: Uncompressed digital audio. The raw format. Largest file size, no processing artifacts.
- LFE: Low-Frequency Effects. The ".1" channel, dedicated to bass below roughly 120 Hz. Fed to a subwoofer.
- Matrix encoding: Technique for embedding additional channels in a stereo signal using phase relationships. Dolby Stereo/Surround/Pro Logic. Approximate, not discrete.
- Discrete channels: Each channel is a separate, independent audio stream. No crosstalk or decoding artifacts.
- Object-based audio: Sounds are assigned 3D spatial coordinates rather than fixed channels. Dolby Atmos, DTS:X. Rendered in real time to available speakers.
- Stems: The individual component tracks (dialogue, music, effects) from the original mix session. Used to create remixes.
- Downmix: Automatic fold-down of a multichannel mix to fewer channels (e.g., 5.1 to 2.0) for playback on simpler systems.
- Re-equalization (Re-EQ): Tonal adjustment applied when playing back a theatrical mix in a home environment. Film mixes are calibrated for large rooms; home playback benefits from a high-frequency rolloff. THX home processors applied this automatically.