Re: [Cellar] matroska and side data vs timecode

[Kieran O Leary <[e-mail]>]

Hi Derek

On Wed, 30 Oct 2019, 15:03 Derek Buitenhuis, <[e-mail]>
wrote:

> Comments inlined below.
>
> On 29/10/2019 16:04, Dave Rice wrote:
>
> *Implementation Considerations:*
>
> Thinking ahead of this work, I think it would be worthwhile to add a
> dedicated section to the Matroska specification on timecode and describe
> two methods for adding a reference timecode to a Matroska Segment.
>
> 1. Using tags. Make an official tag “TIMECODE” to store a string of the
> timecode expression that correlates to the Matroska timestamp of 0. This
> approach is limited to storing timecode that is incremental and continuous.
> Defaults for the incrementation and the behavior of the timecode could be
> described as part of the tag definitions and feasibly another tag or tags
> could be reserved for timecode flags when the timecode behavior is not a
> default. Defining a use of a “TIMECODE” tag would provide the benefit of
> standardizing an existing practice in FFmpeg’s Matroska muxer, where
> rewrapping from a timecode-supportive format to Matroska carries the
> timecode value over as a tag.
>
> To me, requiring timecodes to be incremental and continuous pretty much
> defeats a good chunk of the point of timecodes, no?
>
Kind of, but all tape capture software that I've encountered just stores
the starting timecode value along with framerate and all other timecodes
are based on this starting value. So it won't represent the source
videotape if there's a timecode jump or reset. But the method that Dave
outlines here would at least allow Matroska to mirror what happens with
Aja/blackmagic capture tools using v210/mov as the capture format.
It's very difficult to find tools or examples of noncontinuous timecode
tracks..

Best,

Kieran O'Leary
Irish Film Institute