Time Code and Word Clock
Syncing Audio with Video and MIDI
And 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:
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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
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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 (LowFrequency 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