There are several tools to create Dolby elementary streams, but if you need to play that into a linear system to run through a head end for pass through testing, then we need to wrap the file into something that can be played out of a playback server. Players can support Dolby pass through so long as they can output 24bit 48khz PCM audio transparently, this means your Blackmagic Hyperdeck, Aja Ki Pro or BBright UHD Play or others can support pre-encoded content and feed that into your downstream system.

This process is applicable for the following Dolby codecs

Dolby Digital (.ac3)

Dolby Digital Plus (.ec3)

Dolby AC-4 (.ac4)

Dolby E (.dde)

Encode

The easiest wav to get an encode prepared is with Dolby Media Encoder. Other first Dolby tools do exist, Dolby Encoding Engine (DEE), Dolby Atmos Renderer and various retired softwares can also create Dolby encodes, Dolby Media Generator or the old Dolby Media Producer Suite. You can also create with many third party tools, various video editing NLE (Non-Linear Editing) softwares may have this bundled or various stand alone tools or other services or utilities. Of course you may have your elementary stream already in which case you can skip ahead.

Dolby Media Encoder is available with an evaluation license if you sign up on customer.dolby.com. You can load in a multi channel wav or a Atmos master (damf or ADM) and encode from that. 

You can encode straight to elementary stream here. Some control for loudness and metadata settings may not be available. Dolby Encoding Engine can be a better choice if you have specific parameters to set.

If you would like some example media to try the rest of the workflow with there are pre-encoded Dolby bitstreams available on ott.dolby.com

Note: AC-4 immersive stereo (IMS), TrueHD and Dolby Digital Plus for Blu-Ray are not relevant to the linear workflow covered in this guide.

Demux

You may have an already muxed file like an mp4, you need to demux back to elementary stream to prepare for linear playback. There is a free MP4 demuxer from Dolby here: https://github.com/DolbyLaboratories/dlb_mp4demux

# make the binary executable (mac or linux, mac in this case)
chmod +x mp4demuxer_mac

# demux
./mp4demuxer_mac --input-file /path/to/my/file.mp4 --output-folder /my/output/folder

You can also use ffmpeg (substitute .ec3 with the appropriate file extension for your audio track if it is not Dolby Digital Plus)

ffmpeg -i /path/to/my/file.mp4 -c:a copy my/output/file.ec3

Note: We do not recommend ffmpeg to be used for encoding or decoding any Dolby codecs

SMPTE 337 Wrapping

This is the process preparing an elementary stream for linear playback. This was developed so that we could send coded audio bitstreams around in AES3 compatible audio systems like SDI in linear infrastructure. As long as your AES3 audio data is not sample rate converted, limited or otherwise processed, you can work with coded audio even on these platforms (Blackmagic Hyperdeck, Aja Ki Pro) that are not technically Dolby aware or licensed but can transparently convey the PCM samples.

Note: the play back systems will probably not set the extra AES3 level bits like the non-pcm bit correctly. In practice we have only found a few systems that observe this, and it is usually only to mute a speaker that would otherwise blast out the digital coded audio data as audio samples resulting in some very loud pink noise.

We will use the free tool on github called frame337: https://github.com/DolbyLaboratories/frame337

You may need to install xcode in order to build on MacOS (free from app store) and a Linux system may require some build tools (gcc, build-essentials) windows users will need visual studio to compile the binary.

Mac example process:

First get the source code from github:

git clone https://github.com/DolbyLaboratories/frame337.git

This makes a local copy in your current working directory

Then you cd into the folder

cd frame337

There should be a file called Makefile in here and on Mac (if you have xcode installed) you should just need to type 

make

Shortly after you will see some print out with the last line:

Build of frame337 successfully completed

Then you can move into the new Release folder, I built on Mac so I will then go into the Darwin folder

cd Release/Darwin/

Then you can run the binary like so

./frame337 -i/path/to/my/file.ac4 -o/path/to/my/output.wav

Note: there is no gap between the argument keywords and the path with this tool

This will make a 16bit 48khz stereo .wav file. I like to pad this to 24bit wav (must be done carefully to not resample, dither or limit the data). This is helpful for making the file compatible with playout from SDI player in next steps.

Install soxtool (available on sourceforge)

Then run the wav through to pad up to 24bit:

sox /my/input/file.wav -b 24 /my/output/file_24bit.wav

This effectively adds a byte of 0x00 after each two bytes that were there in the 16bit wav.

Dolby E bitstreams and will default to 24bit wav straight out of frame337.

Muxing into a container for playback

Follow the link below to a guide for your NLE of choice

Adobe Premiere Pro

Final Cut Pro (coming soon)

BlackMagic DaVinci Resolve (coming soon)