Quicktime TimeScale 1000 results in wrong fps

[Markus Degen]

Hi there,

when creating Quicktime movies, ffmbc is setting the QT/TimeScale
value at 1000. This is fine with 25fps movies, but with 24fps movies
it can lead to problems with some professional software.

Depending on the length of the movie, Nuke or Tweak's RV is using a
wrong fps value. You can check this by encoding 13 frames with 24fps.
The above software will read 23.9852 as fps value.

The reason is a non integer division of TimeScale/fps (1000/24).

Apple's Quicktime Pro encoder is using a TimeScale value of 600 when
encoding at 24fps, a value of 1000 when encoding at 25 fps.

A possibility to set the TimeScale value with ffmbc would be awesome.

Greets,
M.

[Baptiste Coudurier]

Hi Markus,

On 03/22/2012 07:46 AM, Markus Degen wrote:
> Hi there,
>
> when creating Quicktime movies, ffmbc is setting the QT/TimeScale
> value at 1000. This is fine with 25fps movies, but with 24fps movies
> it can lead to problems with some professional software.

That value is the global timescale of the file. Each track has its own
timescale which is 1/fps and 1/samplerate and that is perfectly accurate.

> Depending on the length of the movie, Nuke or Tweak's RV is using a
> wrong fps value. You can check this by encoding 13 frames with 24fps.
> The above software will read 23.9852 as fps value.
>
> The reason is a non integer division of TimeScale/fps (1000/24).

This is because the wrong value is being used.

[...]

--
Baptiste COUDURIER
Key fingerprint 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA
FFmpeg maintainer http://www.ffmpeg.org

[Markus Degen]

>
> That value is the global timescale of the file. Each track has its own
> timescale which is 1/fps and 1/samplerate and that is perfectly accurate.
>

>

> This is because the wrong value is being used.
>

Not sure if I understand you correctly. Do you mean Nuke/RV read a
wrong Timescale value or ffmbc writes a wrong one?
And if Nuke/RV read a wrong value (value 1000), how come they read a
right value of 600 if the same sequence is create with Quicktime Pro?

Thanks in advance,
M.

[Baptiste Coudurier]

Hi Markus,

The timescale you are mentioning is the global timescale of the file.
It is not meant to be used when computing the frame rate.
When computing the frame rate, the track timescale should be used instead,
and this one should be accurate.

[sile...@gmx.net]

Hallo Babtiste,

The timescale you are mentioning is the global timescale of the file.
It is not meant to be used when computing the frame rate.
When computing the frame rate, the track timescale should be used instead,
and this one should be accurate.

I understand. Since some professional software is reading the wrong global timescale, wouldn't it make sense to have the possibility with ffmbc to set the timescale to 600? Within my tests it seems that the Quicktime exporter sets the global timescale to 600 with 24/30fps and to 1000 with 25fps.
Best,
Markus

[Baptiste Coudurier]

Hi,

I don't really see the point, but sure it could be a feature request.