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MPEG2 encoding in compressor bitrate issues

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Abigail Isaac
MPEG2 encoding in compressor bitrate issues
on Oct 15, 2009 at 3:48:55 am

Hi

I'm having a problem encoding MPEG2 in compressor.
I'm new to this and have read up as much as i can but still having some problems.
My MPEG2 specs are Program Stream, 640X480 square pixel aspect ratio, progressive, minimum bitrate of 15mbps, long GOP.

My work flow is..
Ripping DVDs with MPEG Streamclip to quicktime file using DV codec and deinterlacing.
Importing to FCP, keeping the sequence settings the same as my clip settings, apart from changing the field dominance to 'none' and the compression settings to 'progressive'
Then blowing up the image slightly so that there are no inactive pixels around the edges.
Exporting to Compressor customising the settings to my specs.

For some of the files I've encoded, this process has worked perfectly but for a few I can't seem to raise the bitrate higher than 13 or 14mbps no matter how high i raise the bitrate settings in compressor.

I have tried rendering and exporting to quicktime, then bringing the quicktime ref into compressor but it hasn't helped.

Can someone tell why this is?

I assume I'm using the correct workflow as it's worked for some of the videos?

Would appreciate any ideas.
Thanks
Abi


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Daniel Low
Re: MPEG2 encoding in compressor bitrate issues
on Oct 15, 2009 at 8:11:35 am

I have to ask, why you earth are re-encoding DVDs at 15Mb/s?

[Abigail Isaac] "For some of the files I've encoded, this process has worked perfectly but for a few I can't seem to raise the bitrate higher than 13 or 14mbps no matter how high i raise the bitrate settings in compressor. "

Where are you getting a readout of the final bitratre?

For those that fall below the 15Mb/s, what type of content are they (Simple, fast moving, complex, detailed etc)

[Abigail Isaac] "I assume I'm using the correct workflow as it's worked for some of the videos? "

As I have alluded to, your workflow is strange but maybe it's the best way you have found to achieve a certain something? Let us know what you are actually trying to achieve and maybe we can help further.



__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."

Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"

Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Abigail Isaac
Re: MPEG2 encoding in compressor bitrate issues
on Oct 15, 2009 at 10:14:25 pm

Hi Daniel,

Thanks so much for your reply. These are the specs requested by apple for itunes video upload. I was getting the readout for the MPEG from movie inspector in quicktime. I've since opened the MPEG in streamclip to get stream info. Here in 'video tracks' info the bitrate is a lot higher. So I'm guessing/hoping this is the information I should be looking at?
I've sent a test run to apple and waiting to hear back. In the meantime, do you have any other suggestions as to how i might change my 'strange' workflow. This is my first attempt so I'm very interested to hear other solutions.

Thanks again,
Abi


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Daniel Low
Re: MPEG2 encoding in compressor bitrate issues
on Oct 15, 2009 at 10:34:56 pm

I'd be very surprised if Apple accept your content, it's possible if the content is unavailable from another source, but the reason Apple ask for 15Mb/s MPEG-2 is because they want very high quality material while still keeping it relatively 'transportable'. As you are ripping from DVD you are simply not giving them that.

I've designed systems for delivery to Apple and I'd always start with at least 50Mb/s I-Frame MPEG-2 for standard def content, this is considered as high as you'd want to go for broadcast quality source material.

What you are doing is taking MPEG-2 that is likely to be at best 5Mb/s and 'trans-rating' that to 15Mb/s; a largely pointless exercise as far as quality is concerned - you can't add quality.

I'd wait to hear back from Apple and then we can take it from there.

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."

Steve Ballmer To USA Today: 30 April 2007

"We and Apple are neck and neck and we're chasing the two
other players,"

Steve Ballmer, referring to Nokia and Research in Motion. October 6th 2009


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Abigail Isaac
Re: MPEG2 encoding in compressor bitrate issues
on Oct 15, 2009 at 11:06:50 pm

Hi Daniel,

I will wait to hear back and get back to you. It may take a week or two. I will also see if I can get the videos to me in a better format.

Thanks again, you've been a great help in my understanding of the process.

Abi



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Adam Milburn
Re: MPEG2 encoding in compressor bitrate issues
on Nov 29, 2009 at 5:20:59 am

Hi Abi and Daniel,

I'm bumping this post as I'm in exactly the same position, and would love to know how you got on.

Apple's specs for upload to iTunes are indeed mpeg-2, minimum 15Mbps, with a max horizontal size of 640.

I'm finding it hard to hit the 15mpbs minimum on videos I am transcoding from 1280 x 720 ProRes 422HQ outputs (which are 80Mpbs). Wondering if, as Daniel suggests, Apple asks for this 15mpbs minimum as a way of maintaining quality, even if in some cases the mpeg-2 program stream never has that much data in it?

Abi, were your videos accepted?

Adam



Audio | Motion | Video
http://www.minkengine.com


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