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General guidelines to broadcast specs + converting 25p to 29.97

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Nick Bacon
General guidelines to broadcast specs + converting 25p to 29.97
on Sep 30, 2012 at 4:52:45 pm

Hello everyone,

Not sure if this is the right forum for this question, so I apologize if this is in the wrong place.

I recently shot a commercial for a client that's set to air on a local affiliate station starting in around a week. I asked the station to give me some guidelines for output specs, but other than "HD, 16x9, 29.97 frames/sec" I wasn't given too much to go on.

So, my first group of questions: what are some good, standard broadcast specs for outputting my project? Is a H.264 MPEG-4 file okay, or should it be uncompressed? Is there a minimum bit rate to hit (I've heard estimates from 6Mbps - 18Mbps)?

Secondly: our client asked us to basically reuse a project that we had done for her earlier. The problem: it was shot at 25p, and so far as I know broadcast needs a 29.97i or 59.94i signal. What's the best way to convert a 25p project to 29.97? I've tried simply changing the export settings in Final Cut/Compressor but when I do I'll get random black frames throughout the project. Also, should the project look interlaced on my monitor? I'm assuming that TV signal corrects for that interlaced look?

Sorry for all the dumb questions. In addition to advice I will also accept criticism and profanity directed at my ignorance. Thanks a lot!


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Andrew Rendell
Re: General guidelines to broadcast specs + converting 25p to 29.97
on Oct 2, 2012 at 9:18:35 pm

For an overview of what broadcast spec is in the UK, this should help
http://www.channel4.com/media/documents/commissioning/PROGRAMME%20MANAGEMEN...

[Specs will be different in different territories so you should get a set from one or more of the mainstream broadcasters where you are.]

I've never come across anyone willing to accept H264. Broadcasting is generally a version of MPEG2, but many places accept a high quality file and create the broadcast data stream themselves. It's unnecessary to go uncompressed, usually ProRes 422 (or 422HQ) or DNxHD (at one of the higher data rates) is fine but you do have to check because different places accept different things. If a station wants you to create an MPEG transport stream they will give you the spec they want.

As a rule broadcasters want 50Mbps 4:2:2 as a minimum, but a lot of 35Mbps 4:2:0 (usually XDCam) does get transmitted.

Frame rate conversions have to be by "motion predictive" conversion (sometimes called motion vector), frame repeating or dropping is not acceptable. That really means proper standards conversion software, not what you get from low cost file conversion programs.


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