title: Timecode Generators and Slaves
---
-
<p>
Ardour supports three common timecode formats:
<abbr title="Linear/Longitudinal Time Code"><dfn>LTC</dfn></abbr>,
<dfn>MIDI Clock</dfn>, as well as
<dfn>JACK-transport</dfn>, a JACK-specific timecode implementation.
</p>
+
<p>
Ardour can generate timecode and thus act as timecode <dfn>master</dfn>,
providing timecode information to other applications. Ardour can also be
<dfn>slaved</dfn> to some external source in which case the playhead
- follows the incoming timecode.<br />
+ follows the incoming timecode.
+</p>
+
+<p>
Combining the timecode slave and generator modes, Ardour can also
<dfn>translate</dfn> timecode. e.g create LTC timecode from incoming MTC.
</p>
-
<h2>Ardour Timecode Configuration</h2>
<p>
This is pretty straightforward: simply turn it on. The MTC and MIDI-Clock
generator do not have any options. The LTC generator has a configurable
output level. JACK-transport cannot be <em>generated</em>. Jack itself is
- always synced to its own cycle and cannot do varispeed — it will
+ always synced to its own cycle and cannot do varispeed—it will
always be synced to a hardware clock or another JACK master.
</p>
</p>
<h3>MTC Generator</h3>
+
<p>
The <dfn>MTC generator</dfn> has no options. Ardour sends full MTC
frames whenever the transport is relocated or changes state (start/stop).
</p>
<h3>LTC Generator</h3>
+
<p>
The level of the <dfn>LTC generator</dfn> output signal can be configured
in in the <kbd class="menu">Preferences > Transport</kbd> dialog. By
default it is set to -18 dBFS, which corresponds to 0dBu in an EBU
calibrated system.
</p>
+
<p>
The LTC generator has an additional option to keep sending timecode even
when the transport is stopped. This mode is intended to drive analog tape
machines which unspool the tape if no LTC timecode is received.
</p>
+
<p>
LTC is send regardless of Ardour's transport speed. It is accurately
generated even for very slow speeds (<5%) and only limited by the
for high speeds.
</p>
-
<h2>Ardour Slave Configuration</h2>
+
<p>
The timecode source can be switched with the button just right of
Ardour's main clock. By default it is set to <kbd
timecode source which is chosen in <kbd class="menu">Edit > Preferences
> Transport</kbd>.
</p>
+
<p>
When Ardour is <dfn>chasing</dfn> (synchronizing to) an external timecode
source, the following cases need to be distinguished:
</p>
+
<ol>
<li>the timecode source shares the clock</li>
<li>the timecode source is independent (no wordclock sync)</li>
</ol>
+
<p>and</p>
+
<ol>
<li>the timecode source uses the same FPS setting as Ardour</li>
<li>the timecode source runs at different frames-per-second</li>
</ol>
+
<p>
In both cases the first option is preferred: clock sync + same FPS setting.
</p>
<h3>Frames-per-second</h3>
+
<p>
If the frames-per-second do not match, Ardour can either re-calculate
and map the frames, or the configured FPS (<kbd class="menu">Session >
> Preferences > Transport > Match session video frame rate to
external timecode</kbd>.
</p>
+
<p>
When enabled, the session video frame rate will be changed to match that
of the selected external timecode source. When disabled, the session video
flash red, and Ardour will convert between the external timecode standard
and the session standard.
</p>
+
<p class="warning">
29.97 drop-frame timecode is another corner case. While the SMPTE 12M-1999
specifies 29.97df as 30000/1001 frames per second, not all hardware devices
follow that standard. The checkbox
<kbd class="option">Lock to 29.9700 fps instead of 30000/1001</kbd> allows
- to use a compatibility mode for those devices.<br />
+ to use a compatibility mode for those devices.
+</p>
+
+<p>
When enabled, the external timecode source is assumed to use 29.970000 fps
instead of 30000/1001. SMPTE 12M-1999 specifies 29.97df as 30000/1001. The
<abbr title="specification">spec</abbr> further mentions that drop-frame
timecode has an accumulated error of -86 ms over a 24-hour period.
Drop-frame timecode would compensate exactly for a NTSC color frame rate
of 30 * 0.9990 (ie 29.970000). That is <em>not</em> the actual rate. However,
- some vendors use that rate — despite it being against the specs
- — because the variant of using exactly 29.97 fps yields zero timecode
+ some vendors use that rate—despite it being against the specs—because the variant of using exactly 29.97 fps yields zero timecode
drift.
</p>
<h3>Clock Sync Lock</h3>
+
<p>
As described in the
<a href="http://manual.ardour.org/synchronization/on-clock-and-time/">On Clock and Time</a>
source is not in sample-sync with the audio hardware (and JACK), Ardour
needs to run at varispeed to adjust for the discrepancy.
</p>
+
<p>
The checkbox <kbd class="option">External timecode is sync locked</kbd>
allows to select the behavior according to your setup. When enabled, it
indicates that the selected external timecode source shares sync (Black
& Burst, Wordclock, etc) with the audio interface.
</p>
+
<p>
In other words: if enabled, Ardour will only perform initial
synchronization and keep playing at speed 1.0 instead of vari-speed
adjusting to compensate for drift.
</p>
+
<p class="note">
Note that vari-speed is unavailable when recording in Ardour, and all
tracking happens at speed 1.0. So if you want to record in sync with
</p>
<h3>MIDI Clock</h3>
+
<p>
<dfn>MIDI Clock</dfn> is not a timecode format but tempo-based time. The
absolute reference point is expressed as beats-per-minute and Bar, Beat
and Tick. There is no concept of sample-locking for MIDI clock signals.
Ardour will vari-speed if necessary to chase the incoming signal.
</p>
+
<p>
Note that the MIDI Clock source must be connected to the
<code>ardour:MIDI clock in</code> port.
</p>
<h3>LTC - Linear Timecode</h3>
+
<p>
The <dfn>LTC</dfn> slave decodes an incoming LTC signal on a JACK audio
port. It will auto-detect the frame rate and start locking to the signal
once two consecutive LTC frames have been received.
</p>
+
<p>
The incoming timecode signal needs to arrive at the
<code>ardour:LTC-in</code> port. Port-connections are restored for each
session and the preference dialog offers an option to select it for all
sessions.
</p>
+
<p>
Ardour's transport is aligned to LTC-frame start/end positions according
to the SMPTE 12M-1999 specification, which means that the first bit of an
the video Frame boundaries.
</p>
-<img src="/ardour/manual/html/diagrams/ltc-transport-alignment.png" title="LTC frame alignment" alt="LTC frame alignment"/>
+<img src="/images/ltc-transport-alignment.png" title="LTC frame alignment" alt="LTC frame alignment"/>
<p><em>Figure: LTC frame alignment for the 525/60 TV standard</em></p>
<p>
speed changes if the <kbd class="optoff">sync locked</kbd> option is
disabled.
</p>
+
<p>
While Ardour is chasing LTC, the main transport clock will display the
received Timecode as well as the delta between the incoming signal and
Ardour's transport position.
</p>
+
<p>
A global offset between incoming timecode and Ardour's transport can be
configured in <kbd class="menu">Session > Properties</kbd>.
</p>
+
<p>
The user-bits in the received LTC frame are ignored.
</p>
<h3>MTC - MIDI Timecode</h3>
+
<p>
Ardour's MTC slave parses <dfn>full timecode messages</dfn> as well as
MTC <dfn>quarter-frame messages</dfn> arriving on the
<code>ardour:MTC in</code> port. The transport will only start rolling
once a complete sequence of 8 quarter frames has been received.
</p>
+
<p>
Ardour supports vari-speed and backwards playback but will only follow
MTC speed changes if the <kbd class="optoff">sync locked</kbd> option
is disabled.
</p>
+
<p>
When Ardour is chasing MTC, the main transport clock will display the
received Timecode as well as the delta between the incoming signal and
</p>
<h3>JACK Transport</h3>
+
<p>
When slaved to jack, Ardour's transport will be identical to
JACK-transport. As opposed to other slaves, Ardour can be used to control
the JACK transport states (stopped/rolling). No port connections need to
be made for jack-transport to work.
</p>
+
<p>
JACK-transport does not support vari-speed, nor offsets. Ardour does not
chase the timecode but is always in perfect sample-sync with it.
</p>
+
<p>
JACK-transport also includes temp-based-time information in Bar:Beats:Ticks
and beats-per-minute. However, only one JACK application can provide this
projects / ardour-manual-diverged / blobdiff