Transcript CALM Down?
CALM DOWN! -24 LKFS Show -24 LKFS Show -21 LKFS 3 -24 LKFS Show -21 LKFS 4 Downmix Dilemma Surround Mix Ls Lf L C Rf R Rs 5 Frequent Downmix Producers • Stereo Deliverables Networks • Stereo Channels & Internet Distribution Stations • Stereo Infrastructure & Channels Consumers • Stereo STBs & TVs (≥61%) 6 Downmix Dilemma Surround Mix Ls ? L Lf C ? Rf Rs R ? 7 Surround Mix Preserve Center L 0 dB Near Field C +6 dB R Average +3 dB 8 Preserve Center Surround Mix Ls ? Lf C L ∑ R -3 dB Rf Rs ∑ ? 9 Preserve Rear? Surround Mix Ls Lf C Rf ∑ L Can't Hear Dialog! -3 dB ∑ R Rs 10 Adjust Rear Surround Mix Ls -3 dB Lf C L ∑ R -3 dB Rf Rs ∑ -3 dB 11 Defacto Standard Downmix Surround Mix Ls -3 dB Lf C L ∑ R -3 dB Rf Rs ∑ -3 dB 12 Defacto-Compatible Surround Mix C 70 dB SPL ∑ C L 70 dB SPL -3 dB ∑ R 13 Incompatible Surround Mix Power Sum 10*Log(3) = 4.8 dB 74.8 dB SPL Lf C Rf Voltage Sum 20*Log (1+.7) = 4.6 dB Lf C Rf ∑ L Power Sum 10*Log(2) = 3 dB 77.6 dB SPL ∑ R 2.8 dB Error! -3 dB 14 Bottom Line If two ads are mixed in surround to measure -24 LKFS… One can sound and measure 2.8 dB louder after downmix Producers can "game" the system to be louder Stations and MVPD's could be deemed non-complaint when broadcasting "compliant" content! Not a problem when content mixed to be compatible A real problem for some Public Television music shows See AES e-Brief 38 for measured statistics "The Effect of Downmixing on Measured Loudness" 15 SOLUTION Customize the Downmix Power Sum 10*Log(3) 74.8 dB SPL Lf C Rf Voltage Sum 20*Log (1+.2) = 1.8 dB Lf C Rf ∑ L ∑ R -12 dB Power Sum 10*Log(2) = 3 dB 74.8 dB SPL 17 Producer-Controlled Metadata Producer Consumer Ls Rf AC3 Audio + Metadata AC3 Audio + Metadata AC3 Decoder C AC3 Encoder Surround Mix Lf Left Right Rs LFE Manual Metadata 18 TV Station-Controlled Metadata Producers Networks TV Stations Consumers Ls AC3 Audio + Metadata AC3 Decoder Rs AC3 Encoder Rf Plant C Distribution Surround Mix Lf Left Right LFE X X No Metadata Channel! X See ATSC A/85 Chapter 7 19 Why No Metadata Channel? Many producers lack interest and ability in setting metadata For a show, requires adoption by ALL distributors Within a network, requires adoption by EVERY station Within a station, requires adoption in ALL equipment Most equipment requires obscure custom settings Some equipment cannot carry metadata Penalty of metadata error is severe: loss of center channel! * * *I'll buy you a beer if you'll let me whine about it. 20 Proposed Solution Standardize downmix for systems without metadata • -3 dB for Center and Rear Require loudness measurement of the standard downmix • • • Encourages producers to mix appropriate to standard downmix Producers can use film-style mixing or shift center channel phase Penalty of an inappropriate mix is merely a show softer in surround Change delivery standards Modify A/85 Ask LKFS meter vendors to include downmix measurement 21 DISCUSSION