# ATSC A/85 Broadcast Loudness Validator Validate audio against ATSC A/85 (CALM Act): -24 LKFS ± 2 LU program loudness per ITU-R BS.1770-4, -2.0 dBTP oversampled true peak, 48 kHz delivery check and a dialnorm cross-check, with a per-file short-term timeline chart. > Canonical page: https://elysiatools.com/en/tools/audio-atsc-a85-validator - **Category:** Media - **Keywords:** atsc a/85, calm act, lkfs, loudness, bs.1770, dialnorm, ac-3, true peak, dbtp, broadcast, television, commercials, fcc, -24 lkfs, us broadcast ## Overview ATSC A/85 is the recommended practice behind US loudness law: the CALM Act made its target binding for US broadcast television as of December 13, 2012, and the FCC enforces it. The anchor number is -24 LKFS (LUFS) with a ± 2 LU tolerance, so the pass window runs from -26 to -22 LKFS, measured over the full program with the ITU-R BS.1770-4 K-weighted, gated method — A/85 measures the whole program, not a dialogue-gated subset. Commercials, promos and programs are held to the same target, which is exactly what the CALM Act polices: ad breaks stop jumping out. The maximum true peak is -2.0 dBTP, oversampled; broadcast chains add transmitter limiting and re-encodes after delivery, so many engineers limit masters at -2.3 dBTP to stay safely inside. ATSC DTV audio is 48 kHz (AC-3/E-AC-3), so non-48 kHz files are flagged. Dialnorm is the metadata field that tells consumer decoders how loud the program is; this tool cross-checks the dialnorm you plan to encode against the measured loudness (recommended value: the measurement rounded to a whole dB) — when they disagree, playback normalisation is wrong even though the audio measured clean. A short-term (3 s) timeline chart shows whether loud moments stay proportionate. Measurement uses FFmpeg's ebur128 filter; files are only read, never modified. ## Inputs - **Program audio (files or ZIP)** (file) - **Content type** (select) - **Expected dialnorm (dB)** (number): e.g. -24 ## When to use - Before delivering commercials, promos, or syndicated program masters to US television networks and local broadcast affiliates. - When auditing audio deliverables to ensure compliance with FCC CALM Act loudness regulations. - When verifying that planned Dolby Digital (AC-3/E-AC-3) dialnorm metadata values match measured program loudness. ## How it works - Upload individual audio files or a ZIP archive, select the content type (program, commercial, or promo), and enter your planned dialnorm metadata value. - The validator scans the audio using ITU-R BS.1770-4 gating to measure integrated loudness (LKFS), maximum true peak (dBTP), sample rate (kHz), and short-term loudness dynamics over time. - Review the interactive HTML report featuring compliance pass/fail badges, dialnorm alignment checks, sample rate confirmation, and a short-term loudness timeline chart. ## Use cases - Validating 30-second commercial spot masters to prevent loudness penalties or rejections under the CALM Act. - Verifying long-form television program delivery packages for syndication and network transmission. - Cross-referencing dialnorm metadata settings against full-mix audio tracks before authoring Dolby Digital bitstreams. ## Frequently asked questions ### What is the acceptable ATSC A/85 loudness target for US broadcast? ATSC A/85 targets -24 LKFS with an allowable tolerance of ±2 LU, creating an acceptable compliance window of -26.0 LKFS to -22.0 LKFS measured across the entire duration. ### What is the maximum allowed true peak level under ATSC A/85? The maximum permitted true peak level is -2.0 dBTP measured with oversampling to prevent inter-sample clipping during downstream transmission encoding. ### Why is 48 kHz sample rate verification required? ATSC digital television standards specify 48 kHz audio for AC-3 and E-AC-3 broadcast delivery, so non-48 kHz files are flagged as non-compliant. ### What is the dialnorm cross-check and why does it matter? Dialnorm is metadata informing consumer decoders of program loudness. If the entered dialnorm value diverges from the measured loudness, playback volume will be improperly scaled on consumer devices. ### Are uploaded audio files modified during the validation process? No. Files are read strictly in non-destructive mode for measurement and analysis; no audio data is re-encoded or altered. ## Related tools - [EBU R128 Broadcast Loudness Validator](https://elysiatools.com/en/tools/audio-broadcast-ebur128-validator): Validate audio against EBU R128: integrated programme loudness at -23.0 LUFS with EBU Mode gating, oversampled true peak at -1.0 dBTP, loudness range (Tech 3342) and momentary / short-term maxima, with a per-file timeline chart. - [CALM Act Commercial Loudness Checker](https://elysiatools.com/en/tools/audio-calm-act-checker): Check whether a commercial is louder than the programme it accompanies, per the FCC CALM Act rules and ATSC A/85: compare average loudness, grade the excess on the A/85 listener comfort scale, and flag loud-opening “gaming” with momentary-loudness diagnostics. - [Audio CD Red Book Checker](https://elysiatools.com/en/tools/audio-cd-red-book-checker): Check album tracks against the Red Book CD-DA standard: 44.1 kHz / 16-bit / stereo PCM, sample peaks, 4-second minimum tracks, 99-track limit, and disc capacity in sectors. - [Audio Gapless Album Validator](https://elysiatools.com/en/tools/audio-gapless-album-validator): Validate an album for gapless playback: inter-track seam gaps, pre-roll and tail silence, encoder delay metadata, and sample-format consistency across every track. - [Normalization History Card](https://elysiatools.com/en/tools/audio-normalization-history-card): Generate a shareable before/after report card for any loudness change: gain applied, LUFS, true peak, sample peak, loudness range, waveforms and third-octave spectral deltas. - [Podcast RSS Enclosure Checker](https://elysiatools.com/en/tools/audio-podcast-rss-enclosure-checker): Validate podcast episode audio against hosting expectations and cross-check it with your RSS feed: enclosure URL / length / type attributes, itunes:duration, GUID uniqueness, RFC 2822 dates, platform codecs and bitrates — byte-exact enclosure lengths included. - [Streaming Loudness Preview](https://elysiatools.com/en/tools/audio-streaming-loudness-preview): Measure your master once, then see the playback gain every major platform will apply — Spotify, Apple Music, YouTube, Tidal, Amazon, Deezer and more. - [Audio Hash](https://elysiatools.com/en/tools/audio-hash): Generate cryptographic hashes (checksums) for audio files ## Samples - [Copyright-Free FLAC Audio Samples](https://elysiatools.com/en/samples/flac-samples): Lossless FLAC audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music - [Copyright-Free MP3 Audio Samples](https://elysiatools.com/en/samples/mp3-samples): Collection of royalty-free audio samples for testing and development purposes including nature sounds, meditation music, and ambient audio - [Copyright-Free WAV Audio Samples](https://elysiatools.com/en/samples/wav-samples): Uncompressed PCM WAV audio samples for testing and development, mirrored from MP3 set with nature sounds and meditation music - [Copyright-Free Raw PCM Audio Samples](https://elysiatools.com/en/samples/pcm-samples): Raw PCM s16le audio samples featuring nature ambience and relaxing music for waveform, playback, and conversion workflows