%dbcent; %extensions; ]> CarlHetherington Hello, and welcome to DCP-o-matic!

DCP-o-matic is a program to generate Digital Cinema Packages (DCPs) from DVDs, Blu-Rays, video files such as MP4 and AVI, or still images. The resulting DCPs will play on modern digital cinema projectors.

DCP-o-matic is free and open-source and is licensed under the GNU GPL.

This manual uses icons from the Tango Desktop Project, with thanks.

To install DCP-o-matic on Windows, download the installer from http://dcpomatic.com/ and double-click it. Click through the installer wizard, and DCP-o-matic will be installed onto your machine. If you are using a 32-bit version of Windows, you will need the 32-bit installer. For 64-bit Windows, either installer will work, but I suggest you used the 64-bit version as it will allow DCP-o-matic to use more memory. You may find that DCP-o-matic crashes if you run many parallel encoding threads (more than 4) on the 32-bit version.

DCP-o-matic will run on Mac OS X version 10.6 (Snow Leopard) and higher. To install it, download the .dmg from http://dcpomatic.com/ and double click to open it. Then drag the DCP-o-matic icon to your Applications folder or wherever else you would like to install it.

You can install DCP-o-matic on Ubuntu 12.04 (‘Precise Pangolin’), 14.04 (‘Trusty Tahr’) or 15.04 (‘Vivid Vervet’) using .deb packages: download the appropriate package from http://dcpomatic.com/ and double-click it. Ubuntu will install the necessary bits and pieces and set DCP-o-matic up for you.

Packages are available for Debian 7 (squeeze), 8 (jessie) and unstable (sid) from http://dcpomatic.com/.

Packages are available for Centos 6.5 and 7 from http://dcpomatic.com/.

Packages for Arch Linux are available from https://aur.archlinux.org/packages/dcpomatic/, thanks to Stefan Karner.

Installation on other Linux systems (for which no packages are available) is quite hard; you will have to compile it from source. If you are using distribution for which no packages are available, do let me know by email and I will look into providing packages on the website. The following dependencies are required: FFmpeg libsndfile OpenSSL libopenjpeg ImageMagick Boost libssh GTK (on Linux) wxWidgets libxml++ xmlsec curl libzip libdcp libcxml Once you have installed the development packages for the dependencies, download the source code from http://dcpomatic.com/, unpack it and run the following commands from inside the source directory: ./waf configure ./waf build sudo ./waf install With any luck, this will build and install DCP-o-matic on your system. To run it, enter: dcpomatic2 in a shell.

In this chapter we will see how to create a video DCP using DCP-o-matic. We will gloss over the details and look at the basics.

Let's make a very simple DCP to see how DCP-o-matic works. First, we need some content. Download the low-resolution trailer for the open movie Sintel from their website. Generally, of course, one would want to use the highest-resolution material available, but for this test we will use the low-resolution version to save everyone's bandwidth bills. Now, start DCP-o-matic and its window will open. First, we will create a new ‘film’. A ‘film’ is how DCP-o-matic refers to some pieces of content, along with some settings, which we will make into a DCP. DCP-o-matic stores its data in a folder on your disk while it creates the DCP. You can create a new film by selecting New from the File menu, as shown in .

This will open a dialogue box for the new film, as shown in .

In this dialogue box you can choose a name for the film. This will be used to name the folder to store its data in, and also as the initial name for the DCP itself. You can also choose whereabouts you want to create the film. In the example from the figure, DCP-o-matic will create a folder called ‘DCP Test’ inside my home folder (carl) into which it will write its working files.

The next step is to add the content that you want to use. DCP-o-matic can make DCPs from multiple pieces of content, but in this simple example we will just use a single piece. Click the Add file(s)... button, as shown in , and a file chooser will open for you to select the content file to use, as shown in .

Select your content file and click Open. In this case we are using the Sintel trailer that we downloaded earlier. When you do this, DCP-o-matic will take a look at your file. After a short while (when the progress bar at the bottom right of the window has finished), you can look through your content using the slider to the right of the window, as shown in .

Dragging the slider will move through your video. You can also click the Play button to play the content back. Note that there will be no sound, and playback might not be entirely accurate (it may be slightly slower or faster than it should be, for example). This player is really only intended for brief inspection of content; if you need to check it more thoroughly, use another player such as Totem, mplayer or VLC.

In most cases, some adjustments would be made to DCP-o-matic's settings once the content has been added. For our simple test, however, the default values will suffice, so we can go straight onto making the DCP. Choose Make DCP from the Jobs menu. DCP-o-matic will encode your DCP. This may take some time (many hours in some cases). While the job is in progress, DCP-o-matic will update you on how it is getting on with the progress bar in the bottom of its window, as shown in .

When it has finished, the DCP will end up on your disk inside the film's folder. You can then copy this to a projector via a USB stick, hard-drive or network connection. See for details about the files that DCP-o-matic creates. Alternatively, if you have a projector or Theatre Management System (TMS) that is accessible via SCP across your network, you can upload the content directly from DCP-o-matic. See the in .

DCP-o-matic can also be used to create DCPs of one or more still images, perhaps for an advertisement or an on-screen announcement. This chapter shows you how to do it. As with video DCPs, the first step is to create a new ‘Film’; select New from the File menu and the new film dialogue will open as shown in .

Enter a name and click OK. Now we need to add the content. As before, click Add file(s).... For our example, we will add a single image file, as shown in .

As with video DCPs, most of the default settings will be fine for a simple test. The one thing that you might wish to change is the length of the still. Select the Timing tab and you will see a Play length setting, as shown in .

This length is a ‘timecode’: it consists of four numbers. The first is hours, the second minutes, the third seconds, and the fourth frames. Enter the duration that you want and then click Set. Finally, as with video, you can choose Make DCP from the Jobs menu to create your DCP. This will be much quicker than creating a video DCP, as DCP-o-matic only needs to encode a single frame which it can then repeat. The previous chapters showed DCP generation using the default settings. DCP-o-matic offers a range of features to adjust the content that goes into your DCP, and this chapter describes those features in detail.

At the top of the Content tab is a list of the content that will go into our DCP. There can be as many pieces of content as you like, and they can be of the following types: Movie — a file containing some video, probably some audio and possibly some embedded subtitles; for example, a MOV, MP4 or VOB. Sound — a file containing one or more channels of audio; for example, a WAV or AIFF file. Still image — a file containing a single still image; for example, a JPEG, PNG or TIFF file. Moving image — a directory containing many still images which should be treated as the frames of a video. Subtitle — a file containing subtitle which will be superimposed on the image of the DCP. These can be .srt or .xml files. DCP — an existing DCP. To add one or more movie, sound, still-image or subtitle files, select Add file(s)... and choose them from the selector. To add a directory (folder) of images or a DCP, choose Add folder... and choose the directory from the selector. If you select a folder of images DCP-o-matic will open a small dialogue box where you can enter the frame rate that the image sequence should be run at. You can remove a piece of content by clicking on its name and then clicking the Remove button.

Adding existing DCPs to a DCP-o-matic film is a little different to adding other types of content. Most content has to be converted to JPEG2000, the compression scheme used by DCPs, which is a very time-consuming process. Existing DCPs are already in JPEG2000 format so do not require conversion. This means that, provided no settings such as crop are used on the DCP content, picture and sound data will be passed from existing to new DCP unaltered. Encrypted DCPs that are added as content will require a KDM targeted at DCP-o-matic so that DCP-o-matic can decrypt them. You should ask the creator of the imported DCP to provide a KDM for DCP-o-matic's decryption certificate, which can be obtained by clicking Export DCP decryption certificate... from the Keys tab of the Preferences dialog (see ).

Below the content list are the controls to set content properties. To adjust the properties for a piece of content, click its name in the content list. The content property controls will then become active for that piece of content. If you want to change the properties for multiple pieces of content at the same time, select the content in the list by clicking the first piece then clicking the other pieces with shift key held down. Note that not all settings can be changed in this way. The content properties are split up into four sections: Video, Audio, Subtitles and Timing. Not all of these sections will be active for all content types. The controls in each section are described below.

The Video tab controls properties of the image, as shown in .

The first option on this tab is the ‘type’ of the video. This specifies how DCP-o-matic should interpret the video's image. 2D is the default; this just takes the video image as a standard 2D frame. The 3D left/right option tells DCP-o-matic to interpret the frame as a left-right pair, as shown in .

Alternatively the 3D top/bottom option tells DCP-o-matic to see the frame as a top-bottom pair, as shown in .

Another option is 3D alternate which takes the first frame of the content as for the left eye, the second for the right eye, the third for the left, and so on. Finally, you can specify 3D left only or 3D right only if this content contains only the the left or right eye images. This is useful when you have the left and right eye image sets in different files; you can specify one content as 3D left only and another as 3D right only and DCP-o-matic will pick up the appropriate frames from each.

The ‘filters’ settings allow you to apply various video filters to the image. These may be useful to try to improve poor-quality sources like DVDs. You can set up the filters by clicking the Edit button next to the filters entry in the setup area of the DCP-o-matic window; this opens the filters selector as shown in .

After changing the filters setup, you will need to regenerate the DCP to see the effect on the cinema screen. The preview in DCP-o-matic will update itself whenever filters are changed, though of course this image is much smaller and of lower resolution than a projected image!

The Colour conversion setting specifies what colour transforms and gamma correction DCP-o-matic will use when converting the selected content into the XYZ colourspace for the DCP. The easiest way to select the required conversion is to choose one of DCP-o-matic's presets. DCP-o-matic knows how to convert from four common colourspaces: sRGB, Rec. 601, Rec. 709 and P3. If you do not know which preset you should use, refer to the suggestions in . sRGBStill images in RGB, e.g. photographs. Rec. 601Standard-definition content (fewer than about 1000 pixels across) including DVD rips. Rec. 709High-definition content including Blu-Ray rips. P3Content explicitly graded to P3. For other required colour conversions, and if you know what you are doing, you can choose Custom which will open the full colour conversion editing dialogue box:

Alternatively, choose None if your source files are already in the XYZ colour space and require no conversion. DCP-o-matic's colour conversion processes are discussed in much more detail in a separate document colour.pdf.

The crop settings can be used to crop your content, which can be used to remove black borders from round the edges of DVD images, for example. The specified number of pixels will be trimmed from each edge, and the content image in the right of the window will be updated to show the effect of the crop. The fade in and fade out settings can be used to apply linear fades into and out of a piece of content. Specify the time for each, clicking Set after making any changes. The Scale to option governs the shape that DCP-o-matic will scale the content's image into. Select the aspect ratio that your content should be presented in.

At the bottom of the video tab is a short description of what will happen to your video with the current settings. In the example of , DCP-o-matic is telling you that the video file is 1920x1080 pixels and it has square pixels (a pixel aspect ratio of 1.00) hence its display aspect ratio is 1.78:1. Since the controls specify ‘16.9’ for the ratio, DCP-o-matic does not scale the image but pads it to the DCP's container ratio of 1.85:1. For a 2K DCP this is 1998x1080 pixels. This description also gives the frame rate of the content and what will happen to it when it is played at the DCP's frame rate. See for details of DCP-o-matic's frame-rate conversion.

The Audio tab controls properties of the image, as shown in .

The section at the bottom of the audio tab is the ‘audio map’. This governs how sound from the content will be arranged in the DCP. Down the left-hand side of the map is the list of audio channels in the currently-selected piece of content. These are labelled with two numbers; the first is the stream index within the content and the second is the channel number within that stream. Some content will have different streams for different languages or audio mixes. Along the top is each channel in the DCP. A green box means that the corresponding content channel will be copied into the corresponding DCP channel. When content channels are copied into DCP channels they can be done with variable gain. If, for example, you want to copy a channel as-is, you can set a gain of 0dB. Alternatively, if you want to mix two channels into one, you may want to use a gain of -6dB on each one to prevent clipping when the two channels are added. The green boxes of the audio mapping view tell you (very roughly) how much gain is applied to each channel. A full-height box means 0dB (i.e. unity) gain. Any less height indicates lower gain. To map one channel to another with 0dB gain, click in the empty box and it will turn green to reflect the mapping. A second click will turn the mapping back off. To set some other gain, right-click on the box to open the gain menu. This allows you to set Off (no mapping or negative infinity gain), Full (0dB gain), -6dB gain or Edit which allows you to set the required gain precisely. Consider, for example, the case in .

Here, we have two channels in the source which are mapped to left and right, respectively, in the DCP. The full green boxes show that the mapping is at unity gain (0dB) in each case. Imagine that we modify the settings to those shown in

We now have the content's streams mapped to left and right and also mixed together and placed in the DCP's centre channel. The smaller green boxes on the centre mappings show that those channels are added with some non-unity gain; you can see by hovering the mouse pointer over those boxes that the gain for content channels 1 and 2 is -6dB when being sent to the centre channel and 0dB when being sent to left and right.

As a final example, the map in shows the mapping of a 5.1 source into a 5.1 DCP.

‘Audio Gain’ is used to alter the volume of the soundtrack. The specified gain (in dB) will be applied to each sound channel of your content before it is written to the DCP. If you use a sound processor that DCP-o-matic knows about, it can help you calculate changes in gain that you should apply. Say, for example, that you make a test DCP and find that you have to run it at volume 5 instead of volume 7 to get a good sound level in the screen. If this is the case, click the Calculate... button next to the audio gain entry, and the dialogue box in will open.

For our example, put 5 in the first box and 7 in the second and click OK. DCP-o-matic will calculate the audio gain that it should apply to make this happen. Then you can re-make the DCP (this will be reasonably fast, as the video data will already have been done) and it should play back at the correct volume with 7 on your sound-rack fader. Current versions of DCP-o-matic only know about the Dolby CP650 and CP750. If you use a different sound processor, and know the gain curve of its volume control, get in touch. Audio Delay is used to adjust the synchronisation between audio and video. A positive delay will move the audio later with respect to the video, and a negative delay will move it earlier.

The subtitles tab contains settings related to subtitles in your content, as shown in .

DCP-o-matic will extract subtitles from the content, if present, and they can be ‘burnt into’ the DCP (that is, they are included in the image and not overlaid by the projector) or included as a separate subtitle ‘asset’ within your DCP (in which case the projector overlays them onto the image on playback). The difference between these two arrangements is illustrated by and

The advantage of separate subtitles is that the same video content can be used for DCPs in many different languages. This means that only a small text file needs to be changed for each target language, rather than a large video file. It also means that the time-consuming video encoding need only be done once for the project rather than once for every language. Note that subtitles come in two types: text and bitmap. Text subtitles are expressed as plain text and can be either burnt into the image or included as a separate subtitle asset within the DCP. Bitmap subtitles, on the other hand, are expressed as pre-rendered bitmaps. They cannot (yet) be added to the DCP as a separate asset and must be burnt into the image. Select the Use Subtitles check-box to enable these subtitles. Select the Burn subtitles into image check-box to burn these subtitles into the image; if this is not ticked the subtitles will be included separately in the DCP to be rendered by the projector. The X Offset and Y Offset controls move the subtitles around within the image. The offsets are expressed as a percentage of the video frame size; 100% X offset is the entire width of the frame, and 100% Y offset is the entire height. Hence, to move the subtitles down by half the frame height you would use a Y offset of 50%. The X Scale and Y Scale controls scale the subtitles. Scale values of 1 make the subtitles the same size (relative to the size of the image) as they are on the original. Values lower than 1 make them smaller, and values higher make them larger. You can stretch the subtitles in either direction by specifying different values for X and Y scale. Subtitles from DVD and Blu Ray sources are frequently larger (relative to the video frame) than those typically used for DCP, so it is often useful to scale such subtitles down using these controls. The Stream control changes the subtitle stream that is used when the content has more than one.

The timing tab contains settings related to the timing of your content, as shown in .

Most of the timing tab's entries are time-codes. These are expressed as four numbers, as shown in .

Position is the time at which this piece of content should start within the DCP. In most cases, this will be 0:0:0:0 to make the content start at the beginning of the DCP. Full length is the length of the piece of content. This can only be set for still-image content: for video or sound content, it is fixed by the nature of the content file. If still-image content is being used you can set the length for which it should be displayed using this control. Trim from start specifies the amount that should be trimmed from the start of the content. Trim from end specifies the amount that should be trimmed from the end of the content. Play length indicates how long this piece of content will be once the trims have been applied. This will be equal to the full length minus trim-from-start and minus trim-from-end. Video frame rate specifies the frame rate for still-image content. It can also be used to override the detected frame rate of other content if DCP-o-matic has got it wrong. Each timecode control has a Set which you should click when you have entered a new value for a timecode. The Set button will make DCP-o-matic take account of any changes to the corresponding timecode.

This section gives a little more detail about how DCP-o-matic process video as it takes it from a source and puts it into a DCP. Consider, as a somewhat over-the-top example, that we have a 720 x 576 image which is letterboxed with 36 black pixels each at the top and bottom, and the video content within the letterbox should be presented in the DCP at ratio of 2.39:1 within a 1.85:1 frame (such as might happen with a trailer). The source image is shown in .

DCP-o-matic runs through the following steps when preparing an image for a DCP: Crop Scale Place in container First, some amount of the image can be cropped. This is almost always used to remove black borders (letterboxing and/or pillarboxing) around images. In our example image, we would use 36 pixels of crop from the top and bottom. This would give the new image shown in .

The next step is to scale the image. Since this content should be presented in a 2.39:1 aspect ratio inside a 1.85:1 DCP we would select Scope from the Scale to option in the Video tab and Flat from the Container option in the DCP tab. The Scale to option should always be set to the aspect ratio at which the content should be seen. The Container option should be set to the preset that you want to use on the projector. Of course, these two settings will often be the same. Given the scaling and container information, DCP-o-matic will look at the DCP's container size, and then scale the source image up until one or both of its dimensions (width, height or both) fits the size of the container, all the while preserving the desired aspect ratio. In our example here, the DCP's container is specified as 1.85:1 (so that the DCP will play back correctly using the projector's ‘Flat’ preset). At 2K, 1.85:1 is 1998 pixels by 1080. Scaling the source up whilst preserving its 1.85:1 aspect ratio will result in the image hitting the sides of the container first, at a size of 1998 x 836. This gives us a new version of the image as shown in .

The final step is to place the image into the DCP. In this case, since we have a 2.39:1 image that should be presented as a 1.85:1 DCP, we have set the container in the DCP tab to be Scope. Since the content has been scaled to 1998 x 836, and a Flat container is 1998 x 1080, there will be some black bars at the top and bottom of the image. DCP-o-matic shares out this black equally, as shown in .

This chapter describes the settings that apply to the whole DCP. The controls for these settings are in the DCP tab of the main window, as shown in .

The first thing here is the name. This is generally set to the title of the film that is being encoded. If Use ISDCF name is not ticked, the name that you specify will be used as-is for the name of the DCP. If Use ISDCF name is ticked, the name that you enter will be used as part of a ISDCF-compliant name. Underneath the name field is a preview of the name that the DCP will get. To use a ISDCF-compliant name, tick the Use ISDCF name check-box. The ISDCF name will be composed using details of your content's soundtrack, the current date and other things that can be specified in the ISDCF name details dialogue box, which you can open by clicking on the Details button. If you want to take the ISDCF-compliant name that DCP-o-matic generates and modify it, click Copy as name and the ISDCF name will be copied into the Name box. You can then edit it as you wish. The DCP name should not matter (in that it should not affect how the DCP ingests or plays) but projectionists will appreciate it if you use the standard naming scheme as it makes it easier to identify details of the content. The Content Type option can be ‘feature’, ‘trailer’ or whatever; select the required type from the drop-down list. On some projection systems this will affect where your content appears in the projector's server user interface, so take care to select an appropriate type. The Signed check-box sets whether or not the DCP is signed. This is rarely important; if in doubt, tick it. The Encrypted check-box will set whether the DCP should be encrypted or not. If this is ticked, the DCP will require a KDM to play back. Encryption is discussed in . If you use encryption DCP-o-matic will generate a random encryption key for you. To specify your own key, click the Edit.. button next to the key. The Standard option specifies which of the two DCP standards DCP-o-matic should use. If in doubt, use SMPTE (the more modern of the two). At the bottom of the DCP tab are a further two tabs, one each to contain the settings for the DCP's video and audio parts. The Container option sets the ratio of the image in the DCP. If this ratio is different to the ratio used for any content, DCP-o-matic will pad the content with black. In simple cases this should be set to the same ratio as that for the the primary piece of video content. Alternatively, you might want to pillarbox a small format into a Flat container: in this case, select the small format for the content's ratio and ‘Flat’ for the DCP. The Frame Rate control sets the frame rate of your DCP. This can be a little tricky to get right. Ideally, you want it to be the same as the video content that you are using. If it is not the same, DCP-o-matic must resort to some tricks to alter your content to fit the specified frame rate. Frame rates are discussed in more detail in . The Use best button sets the DCP video frame rate to what DCP-o-matic thinks is the best given the content that you have added. The 3D button will set your DCP to 3D mode if it is checked. A 3D DCP will then be created, and any 2D content will be made 3D compatible by repeating the same frame for both left and right eyes. A 3D DCP can be played back on many 3D systems (e.g. Dolby 3D, Real-D etc.) but not on a 2D system. The Resolution tab allows you to choose the resolution for your DCP. Use 2K unless you have content that is of high enough resolution to be worth presenting in 4K. The JPEG2000 bandwidth; setting changes how big the final image files used within the DCP will be. Larger numbers will give better quality, but correspondingly larger DCPs. The bandwidth can be between 50 and 250 megabits per second (Mbit/s). Most commercial DCPs use bit rates between 75 and 125 MBit/s. The Audio Channels control sets the number of audio channels that the DCP will have. If the DCP has any channels for which there is no content audio they will be replaced by silence. You can only set an even number of channels here, since that is required by the DCI standard. If you want an odd number of channels, set the DCP channel count to one greater than you need and the unused channel will be filled with silence. The Processor control allows you to select a process to apply to the audio before it goes into the DCP. Two processes are currently provided: Mid-side decode — this will take a L/R stereo input and extract the common part (corresponding to the ‘Mid’ in a mid-side signal) into the DCP's centre channel. The remaining L/R parts will be kept in the L/R channels of the DCP. This may be useful to make near-field L/R mixes more compatible with cinema audio systems. Stereo to 5.1 up-mixer A — this will take a stereo input and up-mix it to ‘fake’ 5.1. The input L/R are treated as follows: DCP L is input L bandpass-filtered between 1.9kHz and 4.8kHz. DCP R is input R bandpass-filtered between 1.9kHz and 4.8kHz. DCP C is input L mixed with input R, taken down by 3dB and then bandpass-filtered between 150Hz and 1.9kHz. DCP Lfe is input L mixed with input R, taken down by 3dB and then bandpass-filtered between 20Hz and 150Hz. DCP Ls is input L bandpass-filtered between 4.8kHz and 20kHz. DCP Rs is input R bandpass-filtered between 4.8kHz and 20kHz. This upmixing algorithm is due to Gérald Maruccia. Stereo to 5.1 up-mixer B — this uses a different approach: DCP L is input L. DCP R is input R. DCP C is input L + input R taken down by 3dB. DCP Lfe is DCP C bandpass filtered between 20Hz and 150Hz. DCP Ls and Rs are input L - input R with a 20ms delay.

The Show Audio button will instruct DCP-o-matic to examine the audio in your content and plot a graph of its level over time. This can be useful for getting a rough idea of how loud the sound will be in the cinema auditorium. A typical plot is shown in

The plot gives the audio level (vertical axis, in dB) with time (horizontal axis). 0dB represents full scale, so if there is anything near this you are in danger of clipping the projector's audio outputs. There are two plot types: the peak level and the RMS, which can be shown or hidden using the check-boxes on the right hand side of the window. The channel check-boxes will show or hide the plot(s) for the corresponding channels in the DCP. The smoothing slider applies a variable degree of temporal smoothing to the plots, which can make them easier to read in some cases. Obviously the audio plot is no substitute for listening in an auditorium, but it can be useful to get levels in the right rough area.

It is not required that DCPs be encrypted, but they can be. This chapter discusses the basic principles of DCP encryption, and how DCP-o-matic can create encrypted DCPs and KDMs for them.

DCPs can be encrypted. This means that the picture and sound data are encoded in such a way that only cinemas ‘approved’ by the DCP's creators can read them. In particular, this means copies of the DCP can be distributed by insecure means: if an ne'er-do-well called Mallory obtains a hard drive containing an encrypted DCP, there is no way that he can play it. Only those cinemas who receive a correct key delivery message (KDM) can play the DCP.

This section attempts to summarise how DCP encryption works. You can skip it if you like. You may need some knowledge of encryption methods to understand it. We suppose that we are trying to send a DCP to Alice's cinema without a troublemaker called Mallory being able to watch it himself. There are two main families of encryption techniques. The first, symmetric-key encryption, allows us to encode some data using some numeric key. After encoding, no-one can decode the data unless they know the key. The first step in a DCP encryption is to encode its data with some key using symmetric-key encryption. The encrypted DCP can then be sent anywhere, safe in the knowledge that even if Mallory got hold of a copy, he could not decrypt it. Alice, however, needs to know the key so she can play the DCP in her cinema. A simple approach might be for us to send Alice the key. However, if Mallory can intercept the DCP, he might also be able to intercept our communication of the key to Alice. Furthermore, if Alice happened to know Mallory, she could just send him a copy of the key. The clever bit in the process requires the use of public-key encryption. With this technique we can encrypt a block of data using some ‘public’ key. That data can then only be decrypted using a corresponding private key which is different to the public key. The private and public keys form a pair which are related mathematically, but it is extremely hard (or rather, virtually impossible) to derive the private key from the public key. Public-key encryption allows us to distribute the DCP's key to Alice securely. The manufacturer of Alice's projector generates a public and private key. They hide the private key deep inside the bowels of the projector (inside an integrated circuit) where no-one can read it. They then make the public key available to anyone who is interested. We take our DCP's symmetric key and encrypt it using the public key of Alice's projector. We send the result to Alice over email (using a format called a Key Delivery Message, or KDM). Her projector then decrypts our message using its private key, yielding the magic symmetric key which can decrypt the DCP. If is fine if Mallory intercepts our email to Alice, since the only key which can decrypt the message is the private key buried inside Alice's projector. The projector manufacturer is very careful that no-one ever finds out what this key is. Our DCP is secure: only Alice can play it back, since only her projector knows the key (even Alice does not).

There are two steps to distributing an encrypted DCP. First, the DCP's data must be encrypted, and secondly KDMs must be generated for those cinemas that are allowed to play the DCP. The first part is simple: ticking the Encrypted box in the DCP tab of DCP-o-matic will encrypt the DCP using a random key that DCP-o-matic generates. The key will be written to the film's metadata file, which should be kept secure. A DCP that is generated with the Encrypted box ticked will not play on any projector as-is (it will be marked as ‘locked’, or whatever the projector manufacturer's term is). The second part is to generate KDMs for the cinemas that you wish to allow to play your DCP. This is done using the Make KDMs option on the Jobs menu. This will open the KDM dialogue box, as shown in .

In order to generate KDMs for a particular projector, you need to know its certificate. These are usually made available by the projector manufacturers as text files with a .pem extension. DCP-o-matic can store these certificates to make life easier. It stores details of cinemas and screens within those cinemas. Each screen has a certificate for its projector. DCP-o-matic can generate KDMs for any screens that it knows about. To add a cinema, click Add Cinema.... This opens a dialogue box into which you can enter the cinema's name, and optionally an email address. This email address can be used to get DCP-o-matic to deliver KDMs via email, but it is optional. Once you have added a cinema, select it by clicking on its name, then click Add Screen.... The resulting dialogue allows you to enter a name for the screen and load in its certificate from a file. The certificate should be in SHA256 PEM format. Alternatively, certificates for projection systems made by some manufacturers can be downloaded from databases provided by the manufacturer. Currently this is supported for Doremi and Dolby equipment. If you are targeting a screen with equipment by one of these manufacturers you can select Doremi or Dolby from the Server manufacturer selection and then click Download. In the next dialogue box, enter details of the screen and click Download and, all being well, the certificate will be fetched. Using the download system you will need to know the serial number of the media server in use in the screen. Most cinema projection or technical departments will know these serial numbers. Note that the reliability of the manufacturers' certificate databases cannot be guaranteed. It is vital that KDMs are tested by the destination cinema will in advance of show time to identify any problems. Once you have set up all the screens that you need KDMs for, select the CPL that you want to create the KDM for. You can use the drop-down list to select the CPLs in the current film project, or load a CPL from somewhere else. Select the cinemas and/or screens that you want KDMs for and fill in the start and end dates and times. You must also select the type of KDM that you want to generate. If in doubt, use Modified Transitional 1. Finally, choose what you want to do with the KDMs. They can be written to disk, to a location that you can specify by clicking Browse. Alternatively, if you choose Send by email the KDMs will be zipped up and emailed to the appropriate cinema email addresses. Click OK to generate the KDMs.

DCP-o-matic provides a few preferences which can be used to modify its behaviour. This chapter explains those options.

The preferences dialogue is opened by choosing Preferences... from the Edit menu. The dialogue is split into seven tabs.

The general tab is shown in .

If you tick the Set Language checkbox and choose a language from the list, that language will be used for DCP-o-matic. You will need to restart DCP-o-matic to see the new language. The translations for DCP-o-matic have been contributed by helpful users. If your language is not on the last, head to the DCP-o-matic website to read about how to contribute a translation.

When DCP-o-matic is encoding DCPs it can use multiple parallel threads to speed things up. Set this value to the number of threads DCP-o-matic should use. This should normally be the number of processors (or processor cores) in your machine. DCP-o-matic will try to set this up correctly when you run it for the first time.

The Check for updates on startup option, if enabled, will tell DCP-o-matic to check on dcpomatic.com to see if there any newer versions of DCP-o-matic then the one you are running. If so, a dialogue box will open with a link to download the new version. available The Check for testing updates as well as stable ones option will also check for test updates as well as those that are formally ‘released’. This is useful if you like to live on the bleeding edge!

With these controls you can set the issuer and creator strings that will be put into the DCPs which you create.

The defaults tab is shown in .

The options in this tab simply allow you to set up default values for various properties of new films.

The servers tab is shown in .

If Use all servers is ticked DCP-o-matic will locate encoding servers automatically (see ). Instead of this (or in addition) servers can be specified explicitly. To add a server, click Add... and enter the host name or IP address of the server to use.

The Keys tab (shown in ) holds options related to the keys and certificates used in some parts of DCP creation.

At the top of the tab is the chain of certificates that will be used to sign DCPs and KDMs. DCP-o-matic creates a random chain when you first run it and if you are happy to use this chain you can ignore the preferences. Otherwise, you can add or remove certificates from the chain using the Add... and Remove buttons. If you want DCP-o-matic to re-create the certificate chain (using new, random certificates) click Re-make certificates... and specify your organisation and common names in the dialogue box that opens. Underneath the certificate chain is the private key that corresponds to the leaf certificate in the chain. You can specify your own private key by clicking Load.... You must do this if you change the leaf certificate, so that the leaf private key corresponds to the public key held in the leaf certificate. Underneath the details of the certificate chain and private key for signing of DCPs and KDMs is a second chain and key which is used by DCP-o-matic when you import an encrypted DCP as a piece of content. The leaf certificate of this chain contains the public key that should be used when targeting a KDM at DCP-o-matic. If you want to import an encrypted DCP you will need to give the decryption certificate to the distributor of the DCP so that they can generate a DKDM for you. You can save this certificate to disk by clicking Export DCP decryption certificate. As with the signing chain, DCP-o-matic will create a certificate chain and private key for you. You can also choose to load your own certificates and key or re-make the chain and key with new, random values.

TMS preferences The TMS tab (shown in ) gives some options for specifying details about your theatre management system (TMS). If you do this, and your TMS accepts SSH or FTP connections, you can upload DCPs directly from DCP-o-matic to the TMS using the Send DCP to TMS option in the Jobs menu.

Protocol should be set to SCP or FTP as appropriate for your TMS. We know that the Arts Alliance Media (AAM) and the Doremi ranges uses SCP connections, and that Dolby's TMSs use FTP. Do let us know if you use any other type of TMS with the Send DCP to TMS feature. TMS IP address should be set to the IP address of your TMS, TMS target path to the place that DCPs should be uploaded to (which will be relative to the home directory of the SSH or FTP user). Finally, the user name and password are the credentials required to log into the TMS via SSH or FTP. Note that for this to work on Doremi servers you will need to set the PasswordAuthentication option in your server's sshd_config to yes.

The KDM email is shown in .

This is a template for the email that is used to send KDMs out to cinemas. You can change it to say whatever you like. A few ‘magic’ strings will be replaced by information from the KDM that is being sent: $CPL_NAMEDCP title $CINEMA_NAMECinema name $SCREENSName of screen or screens that KDMs are being generated for $START_TIMEThe time from which the KDMs are valid $END_TIMEThe time until which the KDMs are valid The Reset to default text will replace the current KDM email with DCP-o-matic's default.

Advanced preferences The advanced preferences are shown in .

Maximum JPEG2000 bandwidth specifies the maximum bit-rate of JPEG2000 that DCP-o-matic will allow you to create. You are advised to leave this at 250Mbit/s in normal use for maximum DCP compatibility. Allow any DCP frame rate removes the limits on the DCP video frame rates that DCP-o-matic will create. This may be useful for experimentation. Again, you are strongly advised to leave this unticked for normal use. Only servers encode makes DCP-o-matic encode JPEG2000 data only on encoding servers and not on the host. We suggest you leave this un-ticked unless you have a good reason to do otherwise. The four checkboxes labelled Log control what sort of messages DCP-o-matic writes to its log file when creating a DCP. It is useful to leave General, Warnings and Errors ticked as this makes the log files useful for tracking down bugs. The Timing checkbox will enable extra log entries to allow developers to investigate and optimize the speed of DCP-o-matic. It will significantly increase the size of the log files that are generated, so in normal use it is best to leave this unticked.

In an ideal world, a DCP would be created using content at the same video frame and audio sampling rates as the DCP. This is not, however, always possible.

There are some limitations to video and audio frame rates in DCPs. This is complicated by the fact that not all projectors will play DCPs at the same frame rates. It is possible to create a DCP which one projector will play fine, but another (of a different type) will refuse to play, or even refuse to ingest.

The only rates that are (pretty much) guaranteed to work on all DCI projectors are 24 frames per second (fps) for video and 48kHz or 96kHz for audio. If you are sending your DCPs to unknown places it wise to consider using these rates if at all possible.

Many projectors now in the wild support additional video frame rates: 25, 30 and 48 fps.

DCP-o-matic has a few tricks to allow you to use content that is not in one of the ‘approved’ rates. Audio is easy: DCP-o-matic can resample to 48kHz from any source rate with minimal loss in quality. Video rate conversion is harder. DCP-o-matic's basic strategy to deal with a non-supported content rate is to run it at the wrong speed, and to adjust the audio to keep it in sync. Let us consider the example of a 25fps source for which you want to create a 24fps DCP. DCP-o-matic will put the frames from the source directly into the DCP without modification, but will tell the projector to play them back at 24fps. This means that the DCP's video will run slightly slower than the original. If DCP-o-matic did nothing else, the result of this would be that the audio would be running at the original speed with the video running slowly. Hence the audio would drift slowly out of sync. To avoid this, DCP-o-matic also resamples the audio such that the projector will play it too slow by the same amount. Hence it will sound slightly different but will remain in sync with the video. For very low or high frame rates, DCP-o-matic can also skip or duplicate frames.

The Frame Rate control in the DCP tab sets the video frame rate that the DCP will use. Clicking Use best sets the rate to what DCP-o-matic thinks is the best for your content. With this button, DCP-o-matic assumes that the whole range of frame rates (24, 25, 30 and 48fps) are allowable. After this, the Video tab for each piece of content will give a summary of what DCP-o-matic is doing with that content. If you want to experiment with other non-standard frame rates, you can do so by ticking the Allow any DCP frame rate in the Advanced tab of the preferences dialogue (see the ). You are strongly advised to use this only on your own equipment, and only for experimentation purposes.

One way to increase the speed of DCP encoding is to use more than one machine at the same time. An instance of DCP-o-matic can offload some of the time-consuming JPEG2000 encoding to any number of other machines on a network. To do this, one ‘master’ machine runs DCP-o-matic, and the ‘server’ machines run a small program called dcpomatic_server. The master and server machines do not need to be the same type, so you can mix Windows PCs, Macs and Linux machines as you wish.

There are two options for the encoding server; dcpomatic_server_cli, which runs on the command line, and dcpomatic_server, which has a simple GUI. The command line version is well-suited to headless servers, especially on Linux, and the GUI version works best on Windows where it will put an icon in the system tray. To run the command line version, simply enter: dcpomatic2_server_cli at a command prompt. If you are running the program on a machine with a multi-core processor, you can run multiple parallel encoding threads by doing something like: dcpomatic2_server_cli -t 4 to run 4 threads in parallel. To run the GUI version on windows, run the ‘DCP-o-matic encode server’ from the start menu. An icon will appear in the system tray; right-click it to open a menu from whence you can quit the server or open a window to show its status. If you would rather not bother installing DCP-o-matic on your server computers, the other option is to use the live-CD image that you can download from the DCP-o-matic web site. Either burn the image to CD, or write it to a USB stick (using something like unetbootin). Boot a PC from the CD or USB stick and it becomes a DCP-o-matic server without touching your standard operating system install.

DCP-o-matic periodically looks on the local network for servers. Any that it finds are given work to do during encodes. Selecting Encoding Servers from the Tools menu brings up a window which shows that servers that DCP-o-matic has found.

DCP-o-matic does not mind if servers come and go; if a server disappears, DCP-o-matic will stop sending work to it, and will check it every minute or so in case it has come back online. You will probably find that using a 1Gb/s or faster network will provide a significant speed-up compared to a 100Mb/s network.

DCP-o-matic generates a number of files as it makes a DCP. shows the files that might be generated after you have created a DCP for a film called ‘DCP Test’.

The DCP Test folder is the one that you specify when you select the New Film option from DCP-o-matic's menu. Everything is stored inside this folder. DCP-o-matic generates some working files as it goes along. These are as follows: log is a list of notes that DCP-o-matic makes as it goes along. This can be useful for debugging purposes if something goes wrong. metadata stores the settings that you have made for this film: things like cropping, output format and so on. video is where DCP-o-matic writes the DCP's video data as it encodes it. analysis is used to keep the results of audio analysis runs. info contains details of each video frame that DCP-o-matic has written so far. This is used when an encoding operation is interrupted and DCP-o-matic must resume it. Following this is the DCP itself: DCP-TEST_EN-XX_UK-U_51_2K_CSY_20130218_CSY_OV. This contains some small XML files, which describe the DCP, and two large MXF files, which contain the DCP's audio and video data. This folder (DCP-TEST_EN-XX_...) is what you should ingest, or pass to the cinema which is showing your DCP. This chapter collects a few notes on bits of DCP-o-matic that do not fit elsewhere in the manual.

If you cancel a DCP encoding run half-way through, or your computer crashes... fear not. DCP-o-matic takes care to ensure that, in most cases, it can resume encoding from where it left off. When you re-start a DCP creation, using the same settings are a previous run, DCP-o-matic will first check that the existing picture frames are correct, and then resume from where it left off. The checking of existing frames does take some time, but it is much faster than running a full re-encode. This resumption is achieved by writing a digest (hash) to disk for every image frame that is written. On resumption, the existing MXF file for image data is read and its contents checked against the hashes.