majicmike / audio-encoding-kit

Audio Encoding Toolkit

General requirements

• ffmpeg
• ffprobe

Codec-specific requirements

Codec	Encoder
AC-3 (DD)	Dolby Encoding Engine
E-AC-3 (DD+)	Dolby Encoding Engine
TrueHD	Dolby Encoding Engine
AAC	qaac
FLAC	ffmpeg
Opus	ffmpeg /w libopus

Installation

git clone https://github.com/vevv/eat
cd eat
pip install .

pip install -e . can be used instead for an editable instance (see: https://stackoverflow.com/a/35064498)

• run eat with no params to generate an example config in ~/.eat/config.toml.example

Configuration

Binary paths in config should only need to be specified if binary is not in PATH, but they might be necessary if you're using Wine or WSL.

To use with Wine (for DEE/qaac), please ensure wine-binfmt is installed, the binaries are set as executable, and you're launching eat with the correct Wine prefix.

WSL is untested, but I don't anticipate any issues.

Usage

usage: eat [-h] [-v] [-i [INPUT ...]] [-o OUTPUT_DIR] [-f [{dd,ddp,thd,opus,flac,aac} ...]] [-b BITRATE]
           [-m {1,2,6,8}] [--sample-rate {44100,48000,96000}] [--bit-depth {16,24}] [-y] [-d]

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         shows version
  -i [INPUT ...], --input [INPUT ...]
                        audio file(s)
  -o OUTPUT_DIR, --output-dir OUTPUT_DIR
                        output directory (default: cwd)
  -f [{dd,ddp,thd,opus,flac,aac} ...], --format [{dd,ddp,thd,opus,flac,aac} ...]
                        output codec
  -b BITRATE, -q BITRATE, --bitrate BITRATE
                        output bitrate (quality value for aac) for lossy codecs
  -m {1,2,6,8}, --mix {1,2,6,8}
                        specify down/upmix, support varies by codec (default: none)
  --sample-rate {44100,48000,96000}
                        change output sample rate (FLAC only)
  --bit-depth {16,24}, --bitdepth {16,24}
                        change output bit depth (FLAC only)
  -y, --allow-overwrite
                        allow file overwrite
  -d, --debug           Print debug statements

Default bitrates

Channels	AC-3 (DD)	E-AC-3 (DD+)	Opus	AAC
1	128 kbps	128 kbps	96 kbps	-V127
2	224 kbps	224 kbps	160 kbps	-V127
6	640	1024 kbps	384 kbps	-V127
8	N/A	1536 kbps	512 kbps	-V127

AAC

AAC is configured to use TVBR mode rather than ABR/CBR. This means the output param is a value between 0 and 127 rather than a bitrate target. See https://github.com/nu774/qaac/wiki/Encoder-configuration#tvbr-quality-steps for more details.

Like qaac, eat will accept any value, but it'll internally be clamped to one of the following.

0	9	18	27	36	45	54	63	73	82	91	100	109	118	127

Default value is 127, which is the maximum quality, depending on the source it can result in different bitrates, I've seen it go from 192 kbps and under on some lower quality 2.0 sources to ~490 kbps on 7.1. I'd recommend trying 127 first, and if bitrate is too high, going from 127 to 91 and then moving up.

Remixing support

Channels	AC-3 (DD)	E-AC-3 (DD+)	TrueHD	Opus	FLAC
* -> 1	yes	yes	no	yes	no
* -> 2	yes	yes	no	yes	no
8 -> 6	yes	yes	no	no	no
6 -> 8	N/A	yes	no	no	no
1/2 -> 6/8	no	no	no	no	no

Remixing is handled by the encoder rather than ffmpeg, as AFAIK it doesn't do it very well.

Examples

• DD+5.1 1024 kbps: eat -i audio.flac -f ddp -b 1024
• TrueHD + DD5.1 640 kbps "core": eat -i audio.dts -f thd dd -b 640

Notes

• Files are processed in order; if multiple formats are passed, each file will be encoded to every format before processing the the next one.
• Support for layouts other than 1.0, 2.0, 5.1, 7.1 depends on the encoder (DEE will only accept those), it's recommended that user converts them beforehand.
• 7.1 will automatically be downmixed to 5.1 with DEE for DD.
• Temp files (including thd.log/thd.mll) are cleaned after each encoding job

TODO

• Threading support / multiple simultaneous encodes
• Test with WSL

Credits

Thanks to pcroland for his deew project which was the base for this (originally a fork, ended up rewritten from scratch). DEE xml config files were used verbatim, and some shared functionality has been added later.