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Compression Spec Questions

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Lisa Olshanski
Compression Spec Questions
on Jan 17, 2014 at 3:43:52 pm

Hi All- I need some help. I got these specs and I'm not even sure if it's possible to do them. I am using Compressor 3.5.3. The original video is a 30 second commercial, Apple Pro Res 1920x1080, 29.97. Is it possible to make a H264 QT under 100MB with a bitrate of at least 50Mbps? I'm not having any luck. Also, for the audio, they are requesting MP3 or AAC and PCM audio. Aren't they 3 separate things? MP3 and AAC compressed and PCM is uncompressed? It seems like there are conflicting things in these specs but I could be wrong. Please help!

Format: MOV or MP4 (HD)
Video Length: :15 or :30 seconds
Size: < 100MB
Codec: H.264 - bitrate must be at least 50 Mbps
Bitrate: Must be at least 50 Mbps
Frames/sec: 24-25 or 29-30 (constant frame rate only)
Aspects Ratio: Native aspects without letteringbox (4:3, 16:9)
Resolution: 1280 x 720 or 1920 x 1080
Audio Codec: MP3 or AAC
2 channels only
PCM Audio
16 or 24 bit only
48 kHz sample rate
Audio is required
Please remove all slates, countdowns, and leaders


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Dave LaRonde
Re: Compression Spec Questions
on Jan 17, 2014 at 5:10:05 pm
Last Edited By Dave LaRonde on Jan 17, 2014 at 5:18:27 pm

[Lisa Olshanski] "The original video is a 30 second commercial, Apple Pro Res 1920x1080, 29.97. Is it possible to make a H264 QT under 100MB with a bitrate of at least 50Mbps?"

Let's do the arithmetic: 50 MB per second, multiplied by 30 seconds would be 1500 MB.... or a little bit over 1 GB. It appears that the answer to your query is "no".

So what bit rate could you use and not exceed the 100MB limit? Let's do a little more arithmetic: 100 MB divided by 30 seconds would be about 3.3Mbps, far less than the 50Mbps you hoped you could use.

Well then, what duration of video could you deliver that would be BOTH at the file size limit and at the desired bit rate? More arithmetic: 100 MB divided by 50Mbps would be two seconds, a lot shorter than your 30-second spot.

It would be interesting to know who came up with these totally unrealistic, fantasy-land delivery specs for you to meet. They apparently don't know how to multiply or divide... or they are great believers in magic.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Alan Okey
Re: Compression Spec Questions
on Jan 17, 2014 at 5:17:46 pm

[Dave LaRonde] "Let's do the arithmetic: 50 MB per second"

That should be megabits per second, not megabytes.


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Dave LaRonde
Re: Compression Spec Questions
on Jan 17, 2014 at 5:23:21 pm

Cool, you can do the calculations for this exercise.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Lisa Olshanski
Re: Compression Spec Questions
on Jan 17, 2014 at 5:43:49 pm

There are 8 bits in a byte so 50 mbps/8=6.25MBx 30 sec=187.5 MB file. So, that wouldn't work. 100MB file/6.25MB=16 sec. So, that wouldn't work either. Thanks for helping with the math, Dave. And thanks for pointing out the different between bits and bytes Alan. Any thoughts on the audio? You can't have something be MP3 and PCM or AAC and PCM, right?

Thanks for your help!


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Dave LaRonde
Re: Compression Spec Questions
on Jan 18, 2014 at 12:21:56 am
Last Edited By Dave LaRonde on Jan 18, 2014 at 12:55:28 am

Yeah, I was off by a factor of 8, your arithmetic is correct, and YES! You can make an MP3 with AAC audio..... which will probably get you in just under the wire. Whew!

Just in case, would they quibble over a few extra bytes here and there?

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Lisa Olshanski
Re: Compression Spec Questions
on Jan 18, 2014 at 2:26:11 am

One more question.... I think.
How do I set constant bit rate for an h.264 Quicktime?


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Dave LaRonde
Re: Compression Spec Questions
on Jan 18, 2014 at 2:28:52 am

How's this for cryptic? Don't make it a variable bit rate.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Lisa Olshanski
Re: Compression Spec Questions
on Jan 18, 2014 at 2:36:31 am

Hey! I thought you're supposed to help people! :-) I don't know where in compressor to choose vbr or cbr when I'm making a h264 qt. I don't see it anywhere.


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