QT render for commercial broadcast?

Kevin R wrote on 5/2/2012, 9:12 PM
I have a copy of the following (severely lacking) specs from my local TV station:

Container: Quicktime movie
Frame rate: 29.97
Codec: H.264 (limit data rate to 25 or 50 Mbps (24414 kbits/sec)
Acceptable frame sizes: 1920x1080, 1280x1080, 1440x1080
Audio: uncompressed (.aiff) 48 kHz 24-bit
AUDIO PEAK LEVEL MUST NOT EXCEED -12 dB

QUESTIONS
==========
(1) QT doesn't provide an H.264 format --- use MPEG-4 Video here?
(2) The QT audio tab only provides a bit depth of 16. ???
(3) Do I limit the data rate to 25 or 50? Which is it, guys? Come on!!
(4) PEAK LEVEL MUST NOT EXCEED -12 dB? What!?

I contacted the station "tech" guy and he's kinda clueless. He told me to disregard the peak level requirement, which speaks pretty poorly of their so-called specs...

So, how do I get 24-bit audio into a QT file? And, perhaps, this can be disregarded as well... but why is there no 24-bit option? And if I select the audio format "24-bit Integer" there STILL isn't a 24-bit option! Which leads me to believe only 16-bits are making it into the final output.

Further, if I go with 24-bit Integer, then I get to select Big Endian or Little Endian---since they are a Mac shop, I believe Big Endian is appropriate, no?

Any advice from anyone who has produced a TV broadcast spot? Is there a better external render method I should use (like the DNxHD workflow, which ALSO doesn't have a 24-bit audio selection)? I don't think Handbrake can help with this one.

Much thanks!

Comments

Geoff_Wood wrote on 5/2/2012, 11:50 PM
They mean -12dBFS, which is the only way you can interpet the number, not knowing their playback equipment and vol knob setting !

The maximium allowable peak level I have seen specced for TV is -9dB.

For some Film and TV stuff there are -23dB and -27dB average dialogue level 'standards', but that's different to peak level.

geoff
Kevin R wrote on 5/3/2012, 12:44 AM
Thanks geoff,

The Vegas meters read dbFS, right? I've compressed all my voice over clips fairly heavy. They are limited to -6 dbFS peak, and the RMS is around -19 dbFS for each.

I was a bit worried that submitting -12 db material would play back low, especially because I'm fairly sure I'm not getting 24-bit audio with my deliverables. The station tech said I could ignore the -12 dB limit as he produces to 0 dB in house. Surely they handle limiting in their playback, so I'm going to push a hot audio signal and let them handle it unless directed otherwise.

Can you advise how to get 24-bit audio into a .mov container? And, does MPEG4 = H.264?

Kevin
Geoff_Wood wrote on 5/3/2012, 2:18 AM
"The Vegas meters read dbFS, right?"

There is no other dB within a computer - the others all relate to real physical voltage (power) levels.

OK dBR (relative) could also apply in a computer, but is rarely (never ?) relevant.

I would send peak (normalised to -9dB) as requested. Even in 16 bit there is in reality little discernable quality compromise.

No, sorry, dunno about how to get 24 bits into MOV.

geoff
Kevin R wrote on 5/3/2012, 2:49 AM
"There is no other dB within a computer"

Right. I meant is it accurate/trustable (no built in offset, etc). I could certainly render audio separate, then massage it in SoundForge to limit it to -12 dB.

I suppose I'm stuck with 16 bits as well. QT can interleave separate audio/video streams, but it converts 1080i video into progressive (or at least marks it progressive). Not sure what's going on there, but I don't trust it at the moment. I'll just use Vegas QT MPEG-4 render.

Thx!
[r]Evolution wrote on 5/3/2012, 6:41 AM
I contacted the station "tech" guy and he's kinda clueless.
Apparently... as are you.

I'll just use Vegas QT MPEG-4 render.
Give yourself plenty of time before it's scheduled airing. Deliver the .mp4. Then call them to make sure it's OK. If it is... you're good. If not... you may need to use Adobe Media Encoder, Sorenson Squeeze, Compressor, or the like. If you're delivering to various Broadcast Companies you should probably have an Encoder/Transcoder anyway.

When I'm given Broadcast Specs, which differ depending on the Broadcast Company, they have to be pretty much exact. If not, it will get rejected. I can only imagine that a client coming to you for your expertise would be disappointment to hear they've missed their airtime because of your shortcomings.

- I see no problem delivering what they are requesting.
AtomicGreymon wrote on 5/3/2012, 8:04 AM
And, does MPEG4 = H.264?

It could; H.264 is defined under MPEG-4 Part 10. But MPEG-4 Part 2 is another type of MPEG-4 video that Quicktime supports, and much lower complexity than H.264/AVC (you'll typically find it in use on cheap mobile devices). Any encoder I've ever used that supported MPEG-4 specified which MPEG-4 you were choosing; is there nothing like that in this? Is it actually Quicktime Pro you're using to encode? Remind me never to put down the $30 for that, heh.

As far as getting 24-bit audio into it, I can't say for sure. The *.mov container apparently supports quite a few audio codecs, but that particular encoder you're using may not support creating any higher than 16-bit under its own power. I've never bothered using Quicktime-specific containers (I consider MP4 generic, hijacked by Quicktime) before, so I'm not sure if this exists... but is there such a thing as an *.mov muxer? MKV and MP4 muxers/demuxers have ended up being ridiculously useful for me. If there's a MOV muxer that works similarly, you could encode the audio as a 24-bit AIFF (which the MOV container apparently supports, though I can't say I've ever seen this combination in practice) and mux that along with a raw *.264 video stream into a *.mov file.
rraud wrote on 5/3/2012, 11:09 AM
Audio: uncompressed (.aiff) 48 kHz 24-bit
Many networks have their preferred specs. Generally, the US standard is/was -20dbFS reference level (EU@ -18dB) with program peaks not exceeding -10dBFS.. which would result in rejection (at least here..NYC) However, the current ATSC LU standards differ some as do the allowable specs station to station. .. See: Recommended Practices A/85 – Techniques for Establishing and Maintaining Audio Loudness for Digital Television.
http://www.atsc.org/cms/index.php/standards/recommended-practices/185-a85-techniques-for-establishing-and-maintaining-audio-loudness-for-digital-television