[FFmpeg-devel] [PATCH] Limited timecode support for lavd/decklink

Jonathan Morley jmorley at pixsystem.com
Fri May 25 21:06:47 EEST 2018

That sounds great, Kieran!

The plan with AJA is to leverage the open source ntv2_v4l2 (AJA video for linux driver) to capture audio, video, and timecode over SDI to a standard video for linux virtual device (aka /dev/video0). Then use the ffmpeg support for v4l2 to read it in and again set the TC string on the video stream metadata. I am just getting started after hearing confirmation from the AJA dev that he would add TC support to the ntv2_v4l2. In general video for linux could work as a consistent interface for this when capturing.


> On May 25, 2018, at 10:47 AM, Kieran O Leary <kieran.o.leary at gmail.com> wrote:
> Hi Jonathan,
> On Fri, May 25, 2018 at 6:32 PM, Jonathan Morley <jmorley at pixsystem.com> wrote:
>> Hi Kieran,
>> To answer your question, this change basically takes the first valid TC as a string and sticks it in the video’s avstream metadata dictionary where other muxers and encoders look. It does not make an independent timecode track/stream with samples per frame. That is why I called the patch “limited”. However there doesn’t seem to be many if any parts of ffmpeg that use dedicated timecode streams with individual samples. That is why it still seemed worth submitting my work back as we move on to other solutions.
> It sounds great to me! I think that this type of timecode (just
> storing first value as a string string) is all I've ever really seen
> in the real world(I work in the Irish Film Archive and we have several
> thousand video tapes as well). This is how AJA Control Room and
> Blackmagic Media Express work anyhow. I'm hoping that this will allow
> open source archival capture tools like
> https://github.com/amiaopensource/vrecord to be able to capture
> timecode.
> I look forward to trying it out, as our goal is to be able to use
> vrecord in order to capture tape to FFV1/Matroska. Matroska doesn't
> support data tracks (yet), but ffmpeg does store the starting timecode
> string as a Matroska Tag when it detects a timecode track in a source
> video. I would love if capturing to Matroska from tape could store
> that starting timecode value, but it's a completely seperate issue to
> this patch.
>> I hope that still helps you in your case. I will stay the course to address Marton’s feedback and get this in there.
> yeah it's great, I'm also interested in your AJA work as we also have
> AJA hardware, though as there's no open SDK for AJA, I'm not sure how
> this would integrate into FFmpeg.
> Best,
> Kieran.
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