Some tips on video projection and converting video for film festivals

Projecting video can look good in a cinema if it is done correctly.

Here are some tips on video projection:

-Use a good video processor.
-Use the best audio/video connections.
-Use a cinema technician to calibrate the digital cinema projector.
-2.4 is the recommended gamma for HDTV monitors in a dim enviroment Link:ITU-R BT-1886. 2.2 – 2.6 can be used.
-A non-digital cinema projector should at least be adjusted with the contrast and brightness controls on the projector. You should not clip the whites or crush the blacks.
-You have to decode Stereo sound with Dolby Prologic or similar. Otherwise speech will either sound as it is coming from the right or the left speaker.
-Video Cassettes can be converted to digital files in a visually lossless format like Apple Prores 422 and be played with a HD-SDI device from a computer.
-Alternatively you can convert video to the DCP format with Fraunhofer Easydcp Creator and play the video from digital cinema servers.
I have done this at several film festivals. Fraunhofer Easydcp Creator does not raise the black levels or crush the white level. It displays the d65 white point correctly. It has a fast jpeg2000 decoder that can convert prores 422 quicktime files in real time speed on fast computers. If you only accept SRGB prores 24/25/30 FPS 422 Quicktime files in 1920×1080,1998×1080 and 2048×858 with 5.1 sound as separate 24 bit, 48khz wav files you can convert the films without other software.

The best video scalers:

-have good upscaling algorithms.
-have 10 bit HD-SDI OUT/IN.
-can auto adjust sound sync.
-detect if the source is interlaced (video) or progressive (film).
-detects the correct cadence.
-detects common video mastering errors.
-can switch between anamorphic 16/9, standard 4/3, letter-boxed 4/3.
-have good conversion from one frame rate to another.

A modern scaler that have HD-SDI in/out is the Blackmagic Design Teranex 2D Processor..
It might not have the ease of use of a consumer scaler and it lacks HDCP but it has better upscaling/frame rate conversion.

Review: Blackmagic Design Teranex 2D Processor

Blackmagic Teranex 2D site

The best transmission of video signals:

1.Digital component SDI/HD-SDI
2.HDMI
3.Analog component
4.S-video
5.Composite video

The best transmission of audio:

1. 3 digital AES pairs with 5.1 sound (HDCAM SR)
(You might need 75 ohm BNC to 110 ohm XLR adapters)

2. Analog 5.1
3. DOLBY E bitstream 5.1 sound (HDCAM)
(you need a DOLBY DMA-8 plus or similar to decode it.)

4. Digital stereo AES pair
(You need a HD-SDI audio de-embedder on some HDCAM Decks. Need to be decoded with Dolby Pro Logic 1/2)
5. Analog stereo
(Dolby Digital is compatible with a lot of cinema equipment, but the professional video cassette formats do not support it)

Do you need a video scaler?
A proper video scaler makes video projection easier.
But if the only video source is HDCAM/Blu-ray you can manage without a video scaler.
I have used HDCAM directly on a Christie digital cinema projector:
-A Christie digital cinema projector can auto detect the field type on the hd-sdi input.
-If the auto detect does not work you can try the different field types until you get a correct picture.
-If the sound needs a delay you can set it in the sound processor.
-You could make different presets on the projector for different aspect ratios.

Converting video to the DCP format
I have converted video material to DCPs at film festivals with the help of After Effects, Pro tools and Fraunhofer Easydcp.
To do this you need to:
-Tell the people who submit films that the films will be converted.
-Have a HD-SDI capture device to capture digibeta and HD-CAM cassettes to prores hq 422 quicktime.

-Have a computer that can capture the video cassettes to Prores 422 Quicktime files. Like a Mac Mini.

 

-Ask for HD prores quicktime video files with separate 5.1 sound to make the conversions easier.

The video material I work with are mostly 25 fps and I convert them to 25 fps DCPs.

Projecting video with a video scaler and a computer with hd-sdi

Before I started converting all video material to DCPs (2006-2011), I used a computer with a SDI/HD-SDI Card to send the video in it’s native form to a video scaler. This way it is was the chipset in the video scaler that did all the work.
A video scaler:
-Upscales
-Decides if the source is interlaced or progressive
-Decides how to fix mastering errors
-Guess the cadence
-Decides how to convert frame rates…
-The DVDDO scaler I used had buttons for the aspect ratios 4/3, 16/9 and letterbox for standard definition material.
-For HD material the HD-SDI device can be connected directly to the projector.

The equipment I used then has been replaced with cheaper alternatives:

Here are some current video playback solutions:

A mac and a Blackmagic Design Ultrastudio Monitor
– The mac can play prores files in their native form and send it through the thunderbolt cable to the Blackmagic Design Ultrastudio Monitor that sends it to the scaler/projector in either pure 8 bit HDMI or 10 bit HD-SDI.

If you use Final cut x as the playback software, you can upscale and fix aspect ratio errors and then render in a prores 422 project before playback.

– A scaler that accepts audio on HDMI or HD-SDI can be used.

– If you use an audio de-embedder you could connect the HDMI/DVI or HD-SDI directly to the projector if you are only using 1080p HD video.

Another alternative is The Teranex and a Mac with a thunderbolt port:

-you can use the teranex as a video scaler in standalone mode and play HD-CAM cassettes directly with the HD-SDI IN/OUT connections
-you can capture video with it.
-you can play captured video or master Quicktime files through the thunderbolt connection IN/ HD-SDI OUT connection.
-you do not have to decide if the film is interlaced/progressive or decide how to convert framerates.
-you can play 5.1 sound
-you can upgrade to DCP conversion with Fraunhofer Easydcp Creator later and convert the captured video to DCPs.

Notes on the Teranex:
-It can be used instead of After Effects for upscaling and deinterlacing video that is going to be converted to DCP. But it does not yet have 2K upscaling so you are limited to 1080P DCPs.

-The teranex will automatically do some of the things you do manually in After effects.
In fields and pulldown in interpret footage in After Effects you have to find the right cadence, and decide if the material is no field/upper fields/lower fields (progressive/interlaced).
The Teranex does this automatically and support mixed cadence/progressive/interlaced material.
To convert mixed cadence material in After Effects I have used adjustment layers and the fieldkit deinterlacing plugin

-If you can’t show the SMPTE DCP framerates like 30 FPS and need to convert hard telecined material to 24 FPS, this is the box that does it the best.
It can convert these formats to 1080p24, and record them as prores 422:
486i59.94
576i50
720p50
720 p59.94
1080p23.98
1080PsF23.98
1080p24
1080PsF24
1080p25
1080p29.97
1080i50
1080i59.94

-You could make a XLR patch panel that is connected to the digital 5.1 inputs on the cinema sound system, this way you can connect to the terranex using a standard yamaha db-25 to xlr AES cable.

-It does not support HDCP. But if the Terranex is connected to the HD-SDI input on a Doremi IMB, you can switch between DCPs, Terranex and HDMI with HDCP (commercial blu-rays)

Leave a Reply

Your email address will not be published. Required fields are marked *