dBFS audio measure
Posted: Tue Jun 21, 2022 1:56 pm
Hi,
I'm preparing a master DCP package of a short film for a screening at a upcoming international film festival. I've received a list of specifications from the festival and two questions popped into my head while reading it.
1) The festival recommends that the audio tracks have Reference level: -20dBFS. I've read that -20 dBFS is a SMPTE standard and is equivalent to 85 dBSPL, but I was wondering how to check if the audio level is right through DCP-o-matic (the LEQ(m) ?).
I'm attaching two audio graphs. The Source.png is the audio graph of the copy that I've received from the filmmaker, and the Normalized.png is the audio graph of the copy with normalized audio to -20 LUFS and Peak of -1.1 to avoid clipping.
I've also ran a FFmpeg volumedetect filter to both files - this is the results:
Source file:
[Parsed_volumedetect_0 @ 0000022275cd8a80] n_samples: 78328320
[Parsed_volumedetect_0 @ 0000022275cd8a80] mean_volume: -23.3 dB
[Parsed_volumedetect_0 @ 0000022275cd8a80] max_volume: 0.0 dB
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_0db: 4234
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_1db: 17607
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_2db: 32575
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_3db: 42442
Normalized (-20 LUFS).
[Parsed_volumedetect_0 @ 000002117a048a80] n_samples: 78328320
[Parsed_volumedetect_0 @ 000002117a048a80] mean_volume: -22.2 dB
[Parsed_volumedetect_0 @ 000002117a048a80] max_volume: -1.1 dB
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_1db: 1882
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_2db: 6719
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_3db: 15715
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_4db: 31200
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_5db: 57368
I would appreciate any hints about what to look at and if the graph doesn't show any potencial problems with the audio. I will also check the audio level at the cinema, but I wanted to ask about how to check if this reference point is meet.
2) This is a simpler matter: according to guideline in DCP 2.0 Channel tracks (stereo) have to be mapped on 5.1. As seen on the graphs, the film is in Stereo, but I'm assuming they asking about making a 5.1 DCP only with L and R channel used. Does anyone meet with such requirements and can confirm it?
Thank you!
I'm preparing a master DCP package of a short film for a screening at a upcoming international film festival. I've received a list of specifications from the festival and two questions popped into my head while reading it.
1) The festival recommends that the audio tracks have Reference level: -20dBFS. I've read that -20 dBFS is a SMPTE standard and is equivalent to 85 dBSPL, but I was wondering how to check if the audio level is right through DCP-o-matic (the LEQ(m) ?).
I'm attaching two audio graphs. The Source.png is the audio graph of the copy that I've received from the filmmaker, and the Normalized.png is the audio graph of the copy with normalized audio to -20 LUFS and Peak of -1.1 to avoid clipping.
I've also ran a FFmpeg volumedetect filter to both files - this is the results:
Source file:
[Parsed_volumedetect_0 @ 0000022275cd8a80] n_samples: 78328320
[Parsed_volumedetect_0 @ 0000022275cd8a80] mean_volume: -23.3 dB
[Parsed_volumedetect_0 @ 0000022275cd8a80] max_volume: 0.0 dB
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_0db: 4234
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_1db: 17607
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_2db: 32575
[Parsed_volumedetect_0 @ 0000022275cd8a80] histogram_3db: 42442
Normalized (-20 LUFS).
[Parsed_volumedetect_0 @ 000002117a048a80] n_samples: 78328320
[Parsed_volumedetect_0 @ 000002117a048a80] mean_volume: -22.2 dB
[Parsed_volumedetect_0 @ 000002117a048a80] max_volume: -1.1 dB
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_1db: 1882
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_2db: 6719
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_3db: 15715
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_4db: 31200
[Parsed_volumedetect_0 @ 000002117a048a80] histogram_5db: 57368
I would appreciate any hints about what to look at and if the graph doesn't show any potencial problems with the audio. I will also check the audio level at the cinema, but I wanted to ask about how to check if this reference point is meet.
2) This is a simpler matter: according to guideline in DCP 2.0 Channel tracks (stereo) have to be mapped on 5.1. As seen on the graphs, the film is in Stereo, but I'm assuming they asking about making a 5.1 DCP only with L and R channel used. Does anyone meet with such requirements and can confirm it?
Thank you!