Update Timecode from Audio - LTC

Dear everyone,

I would like to update timecode from audio of the footages shot by Sony PXW-X70. The filming format is 4K & 2K XAVC-L with MXF wrapping. But it doesn't work. It only works when using the MOV files which are transcoded from the MXF original footages. May I know if you guys have come across similar problem before? And do you have any advice or solution for me? I don't want to transcode so many times. Thanks very much for your help in advance.

Best regards,
Anna

I'm having the same problem with XAVC-I from a Sony FS7. I hear the LTC fine in the embedded audio channel, but when I choose Update Timecode from Audio - LTC from the context menu in the Media Pool, the timecode does not update.

I've verified that the unit I'm using to feed LTC into the audio channel of the camera is fine, because I was able to use the same unit to feed LTC in a Canon 5D Mark III. Resolve successfully updates the TC from the LTC in the H.264 MOV file from the Canon 5D Mk III, with no issues.


I'm on Resolve Studio 12.3.1.001.

Anna,

I'm not sure if you're using Tentacle Sync like I am, but if you are, I found a workaround.

The Tentacle Sync "Sync Software" for Mac OS X allows you read the LTC from the embedded audio tracks in the XAVC file, thereby updating the file timecode, and then you can re-wrap the XAVC from MXF into MOV, by exporting audio and video as "pass-through."

I was a bit suspicious of re-wrapping XAVC from MXF into MOV, but I pulled the file into Resolve, and exported ProRes clips just fine.

The only weird thing I noticed was that upon importing the MOV XAVC, even though the footage was 23.976, Resolve was for some reason reading it as 24.000. It was no problem--I just updated the frame rate for the Media Pool item by modifying the Clip Attribute in the Media Pool.

To use the "Export" option in the Tentacle Sync "Sync Software," you need to actually physically have a Tentacle Sync unit on hand to connect via USB.

There are many reasons why using cheap non-timecode cameras is a bad idea. This is a good example.

Note that when you feed timecode into a real camera (one that jams code and embeds it with each frame), the timecode has to be in phase with the start of each video frame and has to have a common reference. An audio signal on an unused audio track of a cheap camera is not going to give you 100% reliable sync. It will often drift a frame late or a frame early, mainly because of the lack of reference.

Definitely agree, and the FS7 does embed timecode when the break-out box (BOB) is attached. This LTC solution via audio is just for when the BOB is removed from the FS7 for weight or other ergonomic reasons. For instance, the keeping the BOB attached is not tenable when filming a driver from a passenger seat within some smaller cars.

The LTC is fairly reliable, though--I've used it plenty of times without any issues, sending the audio signal into a ProRes recorder for capture.

The fact that Resolve doesn't seem to be able to read the LTC from XAVC in its native MXF container is troubling. XAVC is an extremely popular Sony codec, and this isn't a wildly complicated feature.

I filed an official bug report when I first noticed this. Has there been any progress in fixing this? Having to re-wrap XAVC-I from MXF into MOV is an annoying step.

I have an open support ticket about this bug, but the Blackmagic rep told me that he's unfortunately unable to give me any kind of timeframe as to if or when they will fix this.

I have worked out an alternative workflow, however, and am posting it here in case folks find it useful.

This $250 app called "LTC Convert" is able to read the LTC in MXF-wrapped XAVC files: https://www.videotoolshed.com/product/l ... ert-auxtc/

LTC Convert can also export an XLS spreadsheet file with the LTC information for each MXF file in a folder of your choosing.

Resolve 12.5 has a new "batch" metadata editing ability which involves exporting, editing, and importing CSVs.

So my suggested workflow is to:

1. Read the embedded LTC in your XAVC [MXF] file from LTC Convert
2. Export an XLS spreadsheet of the LTC from LTC Convert
3. Export a CSV from the Media Pool out of Resolve 12.5
4. Use the XLS from LTC Convert to update the CSV from Resolve
5. Import the updated CSV back into the Media Pool in Resolve

I've done each of these, and the process works. While this whole workflow is a bit elaborate, it's much easier and faster than trying to manually type out the LTC that's being read from the Tentacle Sync Studio app, especially if you have a lot of clips.

Unfortunately, solely relying on the Tentacle Sync Studio app is untenable, for several reasons:

1. The Tentacle Sync Studio app's XML export doesn't include any of the LTC fields in the document, or else I'd just be copying and pasting out of the said XML doc.
2. The "Show Info" function from the Tentacle Sync Studio app produces a floating window on OS X, and the metadata containing the LTC can't be copied to the OS clipboard for use in another app.

I've asked the Tentacle Sync folks about finding a way to copy the "file info" information out of the app, but I haven't received a response yet: http://forum.tentaclesync.com/question/ ... sted-apps/

I hope this helps some other poor soul who also is trying to use Resolve 12.5, XAVC MXF, and LTC from a Tentacle Sync. Good luck!

I'll add this that it's not documented anywhere that the function doesn't work on audio (WAV) files. Which is pretty bizarre and pointless. When you get this kind of setup, it's often from a multitrack DAW output.
To utilize the feature I had to grab a piece of video, create an MOV and bring that into Resolve. This kind of logic belongs in the FCP7 days.

Also, what's described in the thread seems to allude to an issue that has been around for a year now?
viewtopic.php?f=23&t=38055

I've noticed in Resolve Studio 12.5.2.010 on macOS Sierra 10.12.1 (16B2555) that this is all fixed! I'm able to update TC from Tentacle Sync LTC recorded into the audio track of XAVC-I via the contextual menu in the Media Pool. Thank you!