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Old May 22nd, 2009, 03:58 AM   #1
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Math help please for 2 hour web video & 1 GB limit

Hi all,

I have a client who has a Vimeo Plus account. They told me Vimeo Plus has a 5 GB weekly upload rate, so I thought "sweet, I can work with that." The problem is the file size is limited to 1 GB, which sucks.

So I have to figure out what to do. The video is a little over 1 hour 55 minutes. My encoder setting for 720p H264 is set at a constant bitrate of 4,000,000 bits per sec. I use Main Concept in Vegas. At that rate it looks fine, but from what I know, if I were to render the whole thing it would put me way over the 1 GB limit. Suggestions on what to do?

I'm waiting on a reply from my client, but I suggested splitting the video into parts, or I could do 1/2 1080 HD which from my experience looks fine.

I could also try a variable bitrate, but the settings that were suggested here seem much bigger than what I had with a constant bitrate: http://eugenia.gnomefiles.org/images/mainconcept.png So what can I get away with and still have it look nice?

Also, if I were to go 1/2 HD, what bitrate would you recommend to keep the file size down with good quality?

I need help with math since it's not my strong suit. Even with the best encoder settings at 720p, I imagine I'd still need to split the video at least once...and I might even have to do it with 540p. Maybe I could go down to SD, but I'd like to get the best resolution out of this.

Anyway, that should be enough info, let me know what you think!

Thanks!!
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Old May 22nd, 2009, 03:35 PM   #2
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Yeah, those particular VBR settings aren't going to do you much good. However, VBR can be the best for these MP4 intermediate files for Youtube and Vimeo. The problem is, you don't really know until it's done rendering whether you've hit the target or not.

You might try targeting about 1.2Mbps with VBR. Depending on the content and how it was shot, this may be plenty of bitrate. 720p / 1.2Mbps with CBR is a different story - the video would need to be shot and edited with streaming in mind (no noise, well lit, stable camera, limited motion, no dissolves, etc.)

1280x720, aka. 720p is indeed the size that is optimum for these intermediates.

Your client needs to do some math. As you've suggested... but more, because nobody wants to sit for 2 hours straight and look at video. Watch a half-hour chapter, maybe. Then come back later for more. Client really needs to think about the user experience - make chapters.

To your question:
1hr55min of video at 1.2Mbs (cbr) = .987 GB

Split it up into four or more chapters, and you're in the clear for up to a 4Mbps bitrate, which is a lot for MP4 720p.
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Old May 22nd, 2009, 04:43 PM   #3
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Hi Seth,

Thanks for your response! Yes, I think what we're going to do is split it up into 4 chapters, so we should be fine for 720 and the 1 GB limit.

Just out of curiosity what are the "maximum" and "average" numbers you'd recommend for VBR if Eugenia's are too high? I think she's also wrong on the audio. I think a 44.1/128 mp3 would sound better than a 48/128. I'm guessing she got that sampling rate number from what the standard is for DVDs and the ac3 codec.

Thanks again!
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Old May 22nd, 2009, 11:55 PM   #4
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Quote:
Originally Posted by David Horwitz View Post
I think a 44.1/128 mp3 would sound better than a 48/128.
I'm willing to bet no one can tell the difference.

I'm betting the 48KHz audio sample rate for video was created because it divides into all the major video Frames/Sec. rates (24, 25, 30, 50, 60) evenly whereas 44.1 KHz does not, not because of some ultrasonic acoustic quality difference.

So go with 44.1 because the acoustic difference is zip and it uses less storage.
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Old May 25th, 2009, 02:07 PM   #5
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Quote:
Originally Posted by David Horwitz View Post
...Just out of curiosity what are the "maximum" and "average" numbers you'd recommend for VBR if Eugenia's are too high?...
Nothing really wrong with the Eugenia numbers, other than they are too high to meet the 1GB limit for a 1hr55min piece. For something a lot shorter they'd work fine, especially well for high-motion content. For low-motion content you don't need that much data bandwidth... but there's nothing wrong with having it.

Quote:
Originally Posted by Bill Koehler View Post
I'm willing to bet no one can tell the difference.

I'm betting the 48KHz audio sample rate for video was created because it divides into all the major video Frames/Sec. rates (24, 25, 30, 50, 60) evenly whereas 44.1 KHz does not, not because of some ultrasonic acoustic quality difference.

So go with 44.1 because the acoustic difference is zip and it uses less storage.
Bill's right - 44.1 and multiples are the standard in the recording industry, 48KHz and multiples in the film/video industry. But I keep at 48KHz through delivery... why resample the audio down to 44.1? I'd suggest keeping to the standard, it won't hurt much, and might help.
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Old June 5th, 2009, 07:54 PM   #6
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The original audio I had was 44.1, so I'm thinking it's best to keep it that way. 48 will create a larger file when it comes to wav due to more samples per sec, but for mp3 at say 128 kbps, I'm not sure how that will play out...maybe the quality will be theoretically better since it compresses from a wider spectral range?
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