Dolby Digital Plugins for FFmpeg

[modus-ms325c]

I came in a bit late wrt. arriving the news here but today marks what MainConcept calls the first "officially approved and Dolby-certified" plugins for FFmpeg usage.

Said plugins are here:
https://www.mainconcept.com/ffmpeg-dolby

Business email address required to get free demo; Proton Mail addresses are not accepted there.

News post announcing the plugins 17 days back:
https://www.mainconcept.com/mainconc...mpeg?hsLang=en

Blog post here:
https://blog.mainconcept.com/dolby-d...udio-in-ffmpeg

Please direct your further questions to MainConcept.

[Selur]

Using a modified ffmpeg version, so you can't use a ffmpeg version build with your requirements, and you have no clue what's in that modified binary from them.

[FranceBB]

I was trying to download the two PDF but I keep getting a 0byte .zip file.
Also, why are they zipping a PDF file?
Anyway, from what I can read, the plugin adds an official decoder and the relative AC3 and E-AC3 encoders, which are supposed to be able to insert the proprietary Dolby metadata like the dialnorm, something that the current open source encoders cannot do.
When something is encoded with the open source encoders, the lack of dialnorm metadata makes most decoders default to -27 LUFS which makes the encoded stream very quiet and not really usable for OTT/PDL.
Other than that, given that the current open source encoders are reverse engineered, arguably the official Dolby encoders are gonna have a better quality at comparable bitrates, but this needs to be proven/tested.
There doesn't seem to be much more than that. No DAMF input support, no AC4 decoding/encoding support and no DolbyE / DolbyED2 decoding/encoding support either.
All in all, that's pretty disappointing.

[filler56789]

Originally Posted by modus-ms325c

............
Proton Mail addresses are not accepted there.

What the devil?????
Do they work for Czar Putin now? :-/

[junh1024]

Originally Posted by FranceBB

When something is encoded with the open source encoders, the lack of dialnorm metadata makes most decoders default to -27 LUFS which makes the encoded stream very quiet and not really usable for OTT/PDL..

I thought FFMPEG can add the ac3 dialnorm now? FFMPEG AC3 encoder has supposedly recently improved, but needs testing as you said.

[FranceBB]

Originally Posted by junh1024

I thought FFMPEG can add the ac3 dialnorm now?

Ah, yeah, I just checked, it definitely can!
Looks like it supports all the proprietary metadata now, including of course -dialnorm.
That's very nice and definitely a very big upgrade compared to the older version of the encoder.

-per_frame_metadata boolean
Allow Per-Frame Metadata. Specifies if the encoder should check for changing metadata for each frame.

0
The metadata values set at initialization will be used for every frame in the stream. (default)

1
Metadata values can be changed before encoding each frame.


-center_mixlev level
Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo. This field will only be written to the bitstream if a center channel is present. The value is specified as a scale factor. There are 3 valid values:

0.707
Apply -3dB gain

0.595
Apply -4.5dB gain (default)

0.500
Apply -6dB gain

-surround_mixlev level
Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo. This field will only be written to the bitstream if one or more surround channels are present. The value is specified as a scale factor. There are 3 valid values:

0.707
Apply -3dB gain

0.500
Apply -6dB gain (default)

0.000
Silence Surround Channel(s)


mixing_level number
Mixing Level. Specifies peak sound pressure level (SPL) in the production environment when the mix was mastered. Valid values are 80 to 111, or -1 for unknown or not indicated. The default value is -1, but that value cannot be used if the Audio Production Information is written to the bitstream. Therefore, if the room_type option is not the default value, the mixing_level option must not be -1.

-room_type type
Room Type. Describes the equalization used during the final mixing session at the studio or on the dubbing stage. A large room is a dubbing stage with the industry standard X-curve equalization; a small room has flat equalization. This field will not be written to the bitstream if both the mixing_level option and the room_type option have the default values.

0
notindicated
Not Indicated (default)

1
large
Large Room

2
small
Small Room


-copyright boolean
Copyright Indicator. Specifies whether a copyright exists for this audio.

0
off
No Copyright Exists (default)

1
on
Copyright Exists

-dialnorm value
Dialogue Normalization. Indicates how far the average dialogue level of the program is below digital 100% full scale (0 dBFS). This parameter determines a level shift during audio reproduction that sets the average volume of the dialogue to a preset level. The goal is to match volume level between program sources. A value of -31dB will result in no volume level change, relative to the source volume, during audio reproduction. Valid values are whole numbers in the range -31 to -1, with -31 being the default.

-dsur_mode mode
Dolby Surround Mode. Specifies whether the stereo signal uses Dolby Surround (Pro Logic). This field will only be written to the bitstream if the audio stream is stereo. Using this option does NOT mean the encoder will actually apply Dolby Surround processing.

0
notindicated
Not Indicated (default)

1
off
Not Dolby Surround Encoded

2
on
Dolby Surround Encoded

-original boolean
Original Bit Stream Indicator. Specifies whether this audio is from the original source and not a copy.

0
off
Not Original Source

1
on
Original Source (default)

-dmix_mode mode
Preferred Stereo Downmix Mode. Allows the user to select either Lt/Rt (Dolby Surround) or Lo/Ro (normal stereo) as the preferred stereo downmix mode.

0
notindicated
Not Indicated (default)

1
ltrt
Lt/Rt Downmix Preferred

2
loro
Lo/Ro Downmix Preferred

-ltrt_cmixlev level
Lt/Rt Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lt/Rt mode.

1.414
Apply +3dB gain

1.189
Apply +1.5dB gain

1.000
Apply 0dB gain

0.841
Apply -1.5dB gain

0.707
Apply -3.0dB gain

0.595
Apply -4.5dB gain (default)

0.500
Apply -6.0dB gain

0.000
Silence Center Channel

-ltrt_surmixlev level
Lt/Rt Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lt/Rt mode.

0.841
Apply -1.5dB gain

0.707
Apply -3.0dB gain

0.595
Apply -4.5dB gain

0.500
Apply -6.0dB gain (default)

0.000
Silence Surround Channel(s)

-loro_cmixlev level
Lo/Ro Center Mix Level. The amount of gain the decoder should apply to the center channel when downmixing to stereo in Lo/Ro mode.

1.414
Apply +3dB gain

1.189
Apply +1.5dB gain

1.000
Apply 0dB gain

0.841
Apply -1.5dB gain

0.707
Apply -3.0dB gain

0.595
Apply -4.5dB gain (default)

0.500
Apply -6.0dB gain

0.000
Silence Center Channel

-loro_surmixlev level
Lo/Ro Surround Mix Level. The amount of gain the decoder should apply to the surround channel(s) when downmixing to stereo in Lo/Ro mode.

0.841
Apply -1.5dB gain

0.707
Apply -3.0dB gain

0.595
Apply -4.5dB gain

0.500
Apply -6.0dB gain (default)

0.000
Silence Surround Channel(s)

-dsurex_mode mode
Dolby Surround EX Mode. Indicates whether the stream uses Dolby Surround EX (7.1 matrixed to 5.1). Using this option does NOT mean the encoder will actually apply Dolby Surround EX processing.

0
notindicated
Not Indicated (default)

1
on
Dolby Surround EX Off

2
off
Dolby Surround EX On

-dheadphone_mode mode
Dolby Headphone Mode. Indicates whether the stream uses Dolby Headphone encoding (multi-channel matrixed to 2.0 for use with headphones). Using this option does NOT mean the encoder will actually apply Dolby Headphone processing.

0
notindicated
Not Indicated (default)

1
on
Dolby Headphone Off

2
off
Dolby Headphone On

-ad_conv_type type
A/D Converter Type. Indicates whether the audio has passed through HDCD A/D conversion.

0
standard
Standard A/D Converter (default)

1
hdcd
HDCD A/D Converter

I mean, at this point I don't really see any reason to go with a proprietary encoder when the open source one has quite literally everything it needs to be used professionally.
Another big win for the open source community.

[j7n]

I don't think you can have a stream without dialnorm. It always has a value, -31 by default, which means no attenuation. And -27 is only 4 dB quieter. Maybe the output gets quieter with some decoders because the dynamic compression is absent. Last time I looked, open source decoders didn't create it. I takes some space in the bitstream.

Well, the MainConcept encoder is not free. There are already ways of encoding with either TotalCode from RF64, or Adobe Audition.