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Frame count accuracy

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Charbel ReaidyFrame count accuracy
by on Aug 5, 2013 at 11:16:17 am

Hi guys,

I don't know if this was discussed before on the forum or where I can post it but I'm having a weird argument with a TV station that broadcasts at 25fps claiming that my encoded mpeg 1 file that I delivered is 2 frames more than its supposed to be (total frames 127).

My edit on the timeline (Avid MC 3.5 on PC HPxw840 workstation) is exactly 125 frames, and the exported quicktime reference is also showing 125 frames.

* I checked it with MediaInfo and its showing:

- Video length: 125 frames

- Video duration: 5s 0ms

- Audio lenght: 5s 46ms

- Play duration: 5s 46ms



* I checked it with Quicktime player inspector it showed 127 frames.



I tried searching this topic on the internet to know what is right and what is wrong I couldn't find any valid answer.



My questions are:

- Is the encoding process affecting the frame count (I'm encoding with sorenson v4.5)?

- Is the inspector of quicktime player a reliable source of info when it comes to the files metadata, if not how to inspect it accurately?

- Can this problem be from Avid itself?

- How to explain this phenomenon to the TV station?



Big thanks!

C.R.


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Dave LaRondeRe: Frame count accuracy
by on Aug 5, 2013 at 5:14:12 pm

If they're using Quicktime to judge such things, they should be using something else. Quicktime is a notoriously poor guide to frame rates, and it's also tough to judge frame counts with it.

Dave LaRonde
Former Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Charbel ReaidyRe: Frame count accuracy
by on Aug 5, 2013 at 5:25:38 pm

Thank you Dave for the reply, which software do you suggest to accurately check the frame count?

Thanks,

C.R.


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Cassius MarquesRe: Frame count accuracy
by on Aug 5, 2013 at 6:07:07 pm

I'm guessing telling them to trim the last two frames is not an option? People at broadcasting act like robots sometimes.

One question though, since I don't know avid. When you say exaclty 125 frames... Does it start at 0 and goes to 124? Check that out, maybe you're getting one extra frame there, and perhaps another adds up somewhere down the line.


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Charbel ReaidyRe: Frame count accuracy
by on Aug 5, 2013 at 6:25:54 pm

Yes Avid starts at frame 0 and so the count would be 124 frames, additionally Avid will trim the timeline exactly to the length of the sequence so no additional gaps at the end of the sequence and it shows the duration exactly 5 seconds.
No it's not an Option to tell the TV guys to trim those extra frames, sometimes they like to complicate things for no reason.

C.R.


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Dave LaRondeRe: Frame count accuracy
by on Aug 5, 2013 at 6:36:36 pm

Any good editing application will do: Avid, FCP, Vegas, Premiere Pro... you can't go wrong with them. I don't know about the freebie ones like iMovie or Windows movie editor, or whatever they call it.

Any sort of effects application also lives & dies by frames: Motion, Smoke, Inferno, AE... they'll be accurate.

Compression applications? Naaahhhh.... I wouldn't use 'em. It's ususally tough to get to a specific frame, to say nothing of counting frames.

The basic thing is not to trust a player. They're meant for... well, playing a file and not for judging quality.

Dave LaRonde
Former Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Charbel ReaidyRe: Frame count accuracy
by on Aug 5, 2013 at 6:46:39 pm

Yes I actually re-imported the QuickTime file into Avid and it gave correct reading (125 frames) I will also try it on smoke tomorrow, but the wrong count is in the mpeg encoded from this QuickTime which leads me to think that the problem is in the encoder software.

C.R.


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