[Ardour-Users] "Extract LTC from audio and align video" menu option missing from "Transcode/Import Video file" popup

robertlazarski . robertlazarski at gmail.com
Mon Apr 2 19:25:34 PDT 2018

On Mon, Apr 2, 2018 at 2:43 PM, Chris Caudle <chris at chriscaudle.org> wrote:

> On Mon, April 2, 2018 2:52 pm, robertlazarski . wrote:
> > However, the video and audio are out of sync. If I press the F8 record
> > button before I start the video, the audio comes in early. If I press the
> > F8 record button after I start the video, the audio comes in late.
> Back up a minute and explain your recording setup.

Thanks for the reply.

A picture is worth a 1000 words, maybe that will help explain. I am doing a
video project with analog synth / compressor / eq processing on the way in
for the audio, using computers only in post production.

The idea is that the Zoom F8 records 8 tracks to a BWF wav file. The BWF
file from the F8 contains metadata timestamps that I do see. The F8 has a
BNC output for timecode, that I am putting into CH1 of the MP4 video via a
phone and a Irig DUO. CH2 contains a scratch audio track, from one of the
F8 outputs. The plan is to have several more phones doing the same thing at
different angles, but I am not there yet.


> The way timecode is supposed to work is either you have a single source of
> timecode audio that is distributed to all recording devices, or you
> synchronize the free-running timecode generators on each piece of
> equipment, and the generators are supposed to have enough frequency
> accuracy that they will stay synchronized within one frame (ca. 33ms) for
> the time period that you need them to free run.
> Does your setup match either of those descriptions?  It sounds like the
> time code generators you are using are both free running and start over
> (at 00:00:01.00?) when you start recording, as opposed to free running and
> synchronized to time of day so that you get "true" time code on your
> recordings no matter when you start.
> --
> Chris Caudle
The F8 is my single timecode generator source. I do not have a nice camera
like RED, that has a BNC input for timecode. So I am recording LTC on the
phone camera CH1 of its stereo track.

I was seeing that "00:00:01.00" start time of the MP4 LTC but didn't know
what it meant. That was the default of the F8. That was a clue, so I
changed it to RTC and now I see "time of day" timestamps in the LTC, but I
am still not syncing correctly as I am a few seconds off.

Robin had some ideas so I'll reply to him next.
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