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Old 19th August 2009, 12:45   #1  |  Link
LigH
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Specs and limits encoding AVC for HDTV broadcasting?

A question came up in the german doom9/Gleitz board, what kind of limits one may need to set up in an AVC encoder to produce suitable content for a HDTV broadcaster. Not only hard facts like Profile@Level, B/Ref/GOV, average and maximum bitrates, but also soft facts like recommended bitrate variance behaviour.

Of course we could collect statistics from existing broadcasts; but it might be more useful to get a look at first-hand information - and some hints about available software on Macintosh (Apple Quicktime Pro being one of the least recommendable AVC encoders is already known)...

Anyone working in such business?
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Old 19th August 2009, 13:03   #2  |  Link
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Chrome was being an ass, and messed up when I click "post quick reply". Anyway. (EDIT: did that AGAIN, but good thing I saved my post before sending)

I think the limit depends on the decoder.

If you're using x264 (which is obviously recommended for speed and quality, now with 1 pass VBV), you need to set key-int to 24 for fast channel skipping, and VBV of like 20000Kbps.

You can use pretty much any setting you want, but for speed reasons, I think following the BD spec for AVC is a good idea (except cutting the maximum bitrate by half, and NOT require slices), or in other words limit to level 4.0, with 3 b and ref frames being a good idea.
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Old 19th August 2009, 13:09   #3  |  Link
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First off... I pretty sure you are talking about OTA transmission right? DVB-T?

I'm one of those jealous ATSC citizens without a viable H.264 pathway in sight. Everyone knows that broadcasters are just DYING to explain to their customers why their new FCC subsidized settop box doesn't work for their streams.
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Old 19th August 2009, 14:13   #4  |  Link
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German thread

As far as I understood, it is not realtime encoding (I am no native english speaker - is that what you mean by "OTA"?) but pre-encoded, and rather for higher bandwidth (DVB-S/C).
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Old 19th August 2009, 14:27   #5  |  Link
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OTA stands for Over The Air.

It is the same thing for pre-encoded material, except you got more time, so you can use slower settings to get better quality. The same rule of VBV and probably key int still applies.

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Old 19th August 2009, 14:46   #6  |  Link
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I thought something like "on-time arrival"...
__

I could imagine that due to bandwidth sharing in bouquets, broadcasters might prefer not to much and not too sudden bitrate variations?
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Old 19th August 2009, 14:58   #7  |  Link
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Quote:
Originally Posted by LigH View Post
A question came up in the german doom9/Gleitz board, what kind of limits one may need to set up in an AVC encoder to produce suitable content for a HDTV broadcaster. Not only hard facts like Profile@Level, B/Ref/GOV, average and maximum bitrates, but also soft facts like recommended bitrate variance behaviour.
If the question is only about providing video to a broadcaster that will re-encode it with their own equipment, I'd guess that following Blu-ray specs is enough. I would certainly not limit bitrates lower than necessary for L4.0 compliance (or Blu-ray compatible L4.1 when using an encoder that supports slices).
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Old 19th August 2009, 15:07   #8  |  Link
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It sounded rather like "ready-to-broadcast encoding", so without another re-encoding. But I'll ask back.
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Old 19th August 2009, 15:22   #9  |  Link
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It sounded rather like "ready-to-broadcast encoding", so without another re-encoding...
I'm very surprised if any broadcaster/channel takes client-encoded material without finally re-encoding the video to their own specifications. Almost all channels embed logos and other graphics to the video, requiring decoding and encoding. Also the equipment is probably arranged so that there's a real-time encoder at the end of the line and it can't be bypassed.

Even if some broadcaster would support this, it's not possible without providing thorough documentation on the required encoding parameters to the client.

Last edited by nm; 19th August 2009 at 15:25.
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Old 20th August 2009, 06:35   #10  |  Link
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I'm very surprised if any broadcaster/channel takes client-encoded material without finally re-encoding the video to their own specifications. Almost all channels embed logos and other graphics to the video, requiring decoding and encoding. Also the equipment is probably arranged so that there's a real-time encoder at the end of the line and it can't be bypassed.
...plus they're often using statmux.

That said, TV consumption will probably be at least 80% VOD in the next decade or so. Live encoding makes sense for sports and news, but not really for anything with post-production.
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Old 21st August 2009, 18:13   #11  |  Link
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If it's for a simple TV channel, please use HDV / Apple pro ress
If it's for a TV channel with a (not too bad) satellite teleport, there you can use x264 in a stuffed (CBR) ts file : it's easy to decode it to HD-SDI and record it to what TV use : HD-CAM, server, etc...
I don't know a lot of open video file kind who can be used in broadcast, it's mainly manufacter file formats :/
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Old 22nd August 2009, 20:56   #12  |  Link
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Originally Posted by LigH View Post
A question came up in the german doom9/Gleitz board, what kind of limits one may need to set up in an AVC encoder to produce suitable content for a HDTV broadcaster. Not only hard facts like Profile@Level, B/Ref/GOV, average and maximum bitrates, but also soft facts like recommended bitrate variance behaviour.

I tested HD before OG2008 with satellite operator
x264 with AU Delimiter + Manzanita software + Dektec card = work

http://www.lilapple.com/
http://www.dektec.com/
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