Here at Brightfish, we (re)master every DCP that goes to the cinemas. This includes a volume check with optional reduction in dB to avoid spots that are too loud. Our procedure for volume check is R128 based. Because it has no advantages to use this on 5.1 cinema audio that has been mixed for Dolby LEQ(m), we have a special procedure for sound studios that use Dolby Leq(m).
We will not make any changes to a 5.1 sound clip that respects the following requirements:
- Sound is delivered in 1 (one) WAV file with 6 channels, not in 6 separate files.
- Channel layout is the standard L-R-C-LFE-Ls-Rs
- Sampling frequency is 48KHz
- Sampling depth is 24 bit
- Mixed for 24 fps – so the total length of the clip =
total # frames / 24
- Example: 750 frames => WAV length = 750 / 24 = 31.250 sec
- Clip volume may not exceed 85dB Leq(m) – obviously
- Filename ends with .leq<db>.wav with <db> the Dolby Leq(m) rating (may not exceed 85)
- The filename does not contain any spaces or one of these characters: “&%$!#~”
If your sound file meets these 8 requirements, it will be accepted and used as-is.
to check if your WAV file is technically correct, you can use the open-source command line tool ffmpeg.
ffmpeg -i <wav file> should give you
Audio: pcm_s24le (...), 48000 Hz, 5.1, s32 (24 bit), 6912 kb/s