Re: QT Rates
Re: QT Rates
- Subject: Re: QT Rates
- From: Martin Baker <email@hidden>
- Date: Fri, 6 Aug 2010 10:31:14 +0100
FWIW We were previously looking at the duration of the third video sample to calculate the fps but we recently had a customer who reported problems with the wrong fps being detected. The movies he was using were created by Rhozet Carbon Coder and there were inconsistent video sample durations throughout the movie.
So we've now changed the fps calculation so it uses the count of samples in the video track divided by movie duration, so the discrepancies get averaged out. No complaints so far.
Martin
www.digital-heaven.co.uk
www.twitter.com/digitalheaven
www.videospaceonline.com
www.finalcutters.com
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On 6 Aug 2010, at 06:20, Rainer Standke wrote:
> I fully agree, something is not right. The user has actually remedied the situation on his end by re-importing the clips or something like that. I am specifically worried not about this case, but overall about what cases we should anticipate.
>
> As I said, I am aware of first and maybe last frames of clips to be wonky, i.e. not standard length. As a matter of fact I went through the trouble of specifically looking at the second sample and its length to get the sample duration, but that turns out not to work for h264s for some reason.
>
> I guess my question is how does FCP figure out the frame rate of movies, and in what case should we expect to see different frame rates between clip and video?
>
> Thanks,
>
> Rainer Standke
> XMiL Workflow Tools
> http://www.xmil.biz
>
> On Aug 5, 2010, at 22:08 , Piers Goodhew wrote:
>
>> *Normally* I say this:
>>
>> FCP reports the "specified" frame rate of the movie - i.e. the movie says "I'm a 25fps movie" (even though frames can have totally different duration.)
>> QT Player (even the hated new one) reports the frame rate as the duration divided by the number of frames. As it's quite normal to have your first and last frame a bit wonky, you nearly always get some strange decimal number, esp. on short movies.
>>
>> So usually I say "nothing to worry about, move on". But to have QT say exactly 23.98 and FCP 29.97 - I think something more is going on here, something's not right.
>>
>> PG
>>
>> On 06/08/2010, at 2:27 PM, Rainer Standke wrote:
>>
>>> Thanks Marshall. I am aware of the fact that as a format QuickTime allows for each video frame to have a different duration. To my understanding, FCP only deals with QT files that have no more than one video track, right? So, in the context of FCP, and XML files exported from FCP, when would it ever make sense for a QT file to have different rates for the clip and its video file?
>>>
>>> Rainer
>>>
>>>
>>> On Aug 5, 2010, at 20:35 , Marshall Eubanks wrote:
>>>
>>>>
>>>> On Aug 5, 2010, at 9:36 PM, Rainer Standke wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> one of my users came up with something somewhat surprising. He had a QT movie that reported a clip frame rate of 23.98 and a video frame rate of 29.97 within FCP (CMD-9). The genesis was unclear (as in: there was no way to figure out how he had gotten there). The footage had been shot in a Canon still camera (Mark 2 5D?).
>>>>>
>>>>> This leads to the question: Are there ever times when the clip's frame rate is not the frame rate of the video? Or is it safe to assume that the clip's frame rate is always going to be the same as the clip's video's frame rate?
>>>>>
>>>>
>>>> Frames can always be dropped by the encoder so, no, it is not safe to assume that.
>>>>
>>>> Regards
>>>> Marshall
>>>>
>>>>> Thanks,
>>>>>
>>>>> Rainer Standke
>>>>> XMiL Workflow Tools
>>>>> http://www.xmil.biz
>>>>>
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| References: | |
| | >QT Rates (From: Rainer Standke <email@hidden>) |
| | >Re: QT Rates (From: Rainer Standke <email@hidden>) |
| | >Re: QT Rates (From: Rainer Standke <email@hidden>) |