Time Code and Word ClockSyncing Audio with Video and MIDIAnd syncing digital devices

What is Time Code?

•It is a way of SYNCRONIZATION

•It allows different kinds of devices to communicate and sync together

•This can be useful with:▫Audio for Video▫MIDI systems▫Various digital devices

SMPTE Time Code

•When audio is added to video, they need a way to be perfectly in SYNC

•VIDEO is made up of individual frames

•DIGITAL AUDIO is made up of SAMPLES

What is SMPTE?•The Society of Motion Picture and

Television Engineers

•They decided on a UNIVERSAL standard.

Frame Rates

•The time codes depend on the frame rate of the video

•It is usually one of the following:▫24 FPS (Common for film)▫25 FPS (PAL European format)▫29.97 FPS (NTSC American)▫30 FPS (HDTV)

Audio/Video Communication•The audio and video streams are generally

produces from different devices

•Using a universal SMPTE format allows for the audio to stay perfectly in place with the frames

•For example:▫Take 24 video FPS and 48k audio▫That’s 2,000 audio samples for every frame

of video!

Telecine and 3:2 Pulldown

•TELECINE is the process of converting motion picture film to a video format

•3:2 pulldown makes 24 FPS film look proper on a TV broadcasting NTSC 29.97 FPS.

•Luckily, audio is not affected by this process

MIDI Time Code (MTC)

•Remember that MIDI is simply data information

•MTC is simply another form of syncing audio and video

•These are called ‘Quarter-frame’ messages

Word Clock

•Word Clock is DIFFERENT than timecode

•It is for syncing digital devices to avoid data errors

•This can also be useful with:▫Tape machines▫CD Players▫Multiple digital devices

Master Word Clock

•These devices are used to sync it all perfectly▫Antelope▫Drawmer▫Lucid▫Digidesign

Jitter•Jitter is distortion of high-frequency signal

•It is caused during transmission between digital devices

•This is often caused by clock errors and can be avoided by:▫Using a Master Word Clock▫Using quality A/D converters with Jitter

reduction▫Jitter reduction built in to digital units

Syncing in the modern studio

•Syncing is often now done “In the Box”

•Software is designed to sync internally

•Modern digital devices have technology to sync properly and avoid jitter

Surround Sound

•Most common format is 5.1•7.1 is also supported on Blu-Ray

•The ‘.1’ refers to the LFE channel (Low-Frequency emmissions)

•Generally, this is a crossover for the subwoofer, incorporated by the engineers

Uncompressed Audio for Video

•PCM: Pulse Code Modulation

•This is a completely uncompressed file, just like we would save from Pro Tools

•Blu-Ray TrueHD: Linear PCM 8 Channels fully uncompressed! Wow.

DTS and Dolby Digital

•Support surround sound, but are compressed audio formats

•They are considered a ‘CODEC’ almost always found on DVD discs

•About 640 kbps compression rate

Some Other Formats

•DVD Audio▫Up to 192k stereo, 96k full surround▫24-bit audio

•SACD▫Sampling rate up to 2822 khz! (CD is 44.1)▫120dB Dynamic Range (CD is 96)▫Nearly 8GB capacity