[Libav-user] No option to specify dynamic range compression profile in AC3 encoding

Carl Eugen Hoyos ceffmpeg at gmail.com
Fri Feb 16 16:41:52 EET 2018

2018-02-15 21:30 GMT+01:00 Townson, Andrew E <Andrew.Townson at charter.com>:

> According to the ffmpeg documentation the AC-3 encoder has options to access
> all Dolby metadata per the Dolby Metadata Guide link available on
> ffmpeg.org. This is true for all Dolby metadata except the Dynamic Range
> Compression (DRC) profile selection. We are experiencing volume
> discrepancies from set top boxes while playing content encoded from ffmpeg.
> We also use Minnetonka’s Surcode for Dolby Digital 5.1 AC-3 encoding
> software. It does allow the selection of a DRC profile and there are no
> audio discrepancies as seen with ffmpeg. Is this an option that can be added
> or can someone offer a solution to this issue?

Looks like a question for the FFmpeg user mailing list.

> First pass – ouput is parsed as $loudnorm variable with properties:
> ffmpeg.exe -i input.wav -vn -af "loudnorm=print_format=summary" -f null –
> Second pass:
> ffmpeg.exe -i input.wav -vn -c:a ac3 -ac 2 -b:a 192k -ar 48000 -af
> "loudnorm=I=-24:offset=$($loudnorm.Target_Offset_LU):linear=true:measured_I=$($loudnorm.Input_Integrated_LUFS):measured_TP=$($loudnorm.Input_True_Peak_dbTP):measured_LRA=$($loudnorm.Input_LRA_LU):measured_thresh=$($loudnorm.Input_Threshold_LUFS)"
> -dsur_mode 0 -dialnorm -24 -y output.ac3

Complete, uncut console output missing.

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Carl Eugen

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