[FFmpeg-user] Source v210.mov has no interlacement info, ffv1 transcode is listed as progressive

[Kieran O Leary]

Hello Tobias!

On Thu, Jul 28, 2016 at 1:34 PM, Tobias Rapp <t.rapp at noa-archive.com> wrote:

>
> From the top of my head FFV1 has a flag interlaced=false/true but there is
> no interlaced=unknown.
>

According to mediaconch, picture_structure is in fact 3 (progressive).
According to the spec, there is a value for unknown (0) :
0unknown
1top field first
2bottom field first
3progressive
Otherreserved for future use

https://github.com/FFmpeg/FFV1/blob/master/ffv1.md

>> Avid, even though I selected PAL top field first, did not
>> write any interlacement info to the mov from what I can see. Nothing
>> shows up in mediainfo in regards
>> to interlacement for the source v210.mov, and I can't see any fiel
>> atom info in mediatrace. Avid MC8 never seems to write field/aspect
>> ratio in general for the 'send to QT' feature.
>
>
> I guess on this list it might be helpful to use ffprobe for checking file
> properties. Example:
>
> ./ffprobe -show_streams -select_streams v \
>   -show_frames -read_intervals %+1 some-file.mkv
>

Thanks. I'm getting values of 0 for interlaced_frame and
top_field_first in both source and input.

>> Seeing as -vf idet shows TFF values for these files, and the telecine
>> machine that created these files outputs PAL TFF, I am tempted to just
>> use field_order in the source file in order to correct this before
>> transcoding,  but I thought I'd see what ye think anyhow in regards to
>> this issue.
>
>
> In my opinion it is better to detect and apply the interlaced/field_order
> properties early in the conversion chain. If it is left undefined the
> different tools in your conversion chain might use different internal
> defaults.
>

I agree. These are old files that have been on our system for a while
and it's difficult to remember what the actual creation environment
was. We're trying to stipulate everything as early as possible from
now on.

Best,

Kieran.