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Hardware vs. Software with 1-pass CBR

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Glenn Camhi
Hardware vs. Software with 1-pass CBR
on Nov 1, 2011 at 3:35:15 am

If you're using 1-pass CBR at 8.0 Mbps to encode HD footage for a short SD DVD, could using hardware like Sonic Solutions' SD-2000 give you any quality advantage over using Compressor?

(Most of what I see is about VBR or time savings; haven't found much on this specifically.)

Thanks!


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Angelo Lorenzo
Re: Hardware vs. Software with 1-pass CBR
on Nov 1, 2011 at 6:06:50 am

I'm not sure you'd want to. With a piece of hardware that old, I'd venture to guess you'd get an optimized result with a command line software encoder with less hassle than getting an SD-2000 up and running on OS 9.

With that being said, without venturing into paid alternatives like MainConcepts product offerings, I much prefer something like FFMPEG (libavcodec to be specific, as their encoding engine) over Compressor's use of Quicktime's MPEG2 encoding. Granted the former still sees visible benefits from a 2-pass encode.

Quite a bit faster since it will multi-thread more effectively as well.

Angelo Lorenzo
http://filmsfor.us - Helping you sell your film online






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Glenn Camhi
Re: Hardware vs. Software with 1-pass CBR
on Nov 1, 2011 at 6:19:51 am

Thanks Angelo! Interesting. FWIW, I'm not getting the machine up and running, a major finishing place in L.A. uses it. I've assumed whatever they did would be superior to what I could do at home with Compressor.

For 30 minutes on a DVD, is there much advantage to using multipass over 1-pas CBR? Are you talking 2-pass CBR or VBR? If VBR, wouldn't 5-10 passes be better? I know very little about this (clearly), but I thought if you're using a very high bit rate like 8.0 on a DVD, 1-pass CBR is as good as you can get as far as bit rate's concerned.

Anyway, if my options are Compressor at home or the Sonic, which can give me the better looking DVD?


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Angelo Lorenzo
Re: Hardware vs. Software with 1-pass CBR
on Nov 1, 2011 at 6:44:02 am

Compressor and Quictime's internal codecs are pretty abysmal in terms of quality and performance. If the finishing house has the hardware working and it's in your budget, go for it.

It may be worth asking your post house as to the SD-2000's performance, but 1-pass encoding from some encoders can trip up over scenes with flashing lights or crossfades even at high bitrates. This results in compression blocks that look bad for a few frames. 2-pass encoding, either VBR or CBR (2-pass CBR is rare) uses the first pass to gather analytical data about your video and prevent any quantization errors that might occur on a 1-pass-only encode.

VBR is prevalent on 60min+ dvds as you can squeeze out plenty of quality, but regardless of CBR or VBR I'd go for 2-pass if this will be professional quality.

Angelo Lorenzo
http://filmsfor.us - Helping you sell your film online






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Glenn Camhi
Re: Hardware vs. Software with 1-pass CBR
on Nov 1, 2011 at 7:27:51 pm

Thanks to you both for your replies.

Angelo: Yep, pro quality. I haven't been able to find any reliable documentation on what 2-pass CBR does over 1-pass CBR, except that it analyzes what the optimum high bit rate should be and then sets it. If you have room for a CBR of 8.0 Mbps (which seems to be the highest that's generally considered safe for most dvd players) then there'd be no point in 2 passes, right? But if 2-pass CBR does something else, is there any documentation anywhere that explains it?

I thought the point of multiple VBR passes is to analyze where your footage need higher bit rates and where you can save room with lower bit rates. If you don't need to save any room, is there still some advantage? What else is it doing? BTW, I thought quantization errors occur in the other direction, when going from analog to digital, no?

Brad: Similar question -- if 8.0 Mbps is your max as you say, and if there's room on the DVD for the entire video to be at 8.0, why use VBR? That is, what advantage could there be in using lower bit rates in some places? Does something else happen when you use VBR that a constant 8.0 bit rate fails to do? I've never seen any documentation on that so I don't know. Thanks.


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Angelo Lorenzo
Re: Hardware vs. Software with 1-pass CBR
on Nov 1, 2011 at 10:06:51 pm

What CBR and 1-pass VBR do is vary the Q (take this as quality) level to maintain bitrate. Granted 1-pass VBR will fluctuate bitrate to accommodate but you'll never really see big bitrate swings with 1-pass unless you set wide min and max values.

2-pass VBR uses the analytical first pass to determine bitrate for a particular set of frames. Quantization errors, for lack of a better term in this context, is a codecs "bad guess" at a target bitrate.

2-pass CBR, while you are correct in that it sets an average bitrate that works for the whole piece, also avoids these "bad guesses".

Granted these errors are more noticeable at lower bitrates, so maybe I'm extending my paranoia past the scope of your situation.

http://tangentsoft.net/video/mpeg/enc-modes.html isn't a bad quick read.

Angelo Lorenzo
http://filmsfor.us - Helping you sell your film online






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Glenn Camhi
Re: Hardware vs. Software with 1-pass CBR
on Nov 2, 2011 at 8:30:13 pm

Thanks again, Angelo.

For the record, I got the 1-pass CBR version via Sonic from the post house, and have a verdict:

It looks MUCH better than what Compressor produced. Mostly. There are some areas where it fares a bit worse: most notably, thin lines (like phone wires) and computer-generated graphics exhibit very noticeable aliasing that's less pronounced or wholly unnoticeable in the Compressor-encoded version. However, it may be that because the Sonic-encoded version is sharper, any slight aliasing may simply be enhanced. What's weird is that in some places, it's the reverse (more aliasing in the Compressor version than the Sonic one)! No clue why, but overall, the Sonic-encoded video is far superior.


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Brad Elliott
Re: Hardware vs. Software with 1-pass CBR
on Nov 1, 2011 at 3:13:38 pm

I have not had consistently good results with using Compressor to down convert HD for SD DVD.

My solution has been to down-convert the HD in Final Cut by putting the HD footage into a 16x9 29.97 SD sequence and then rendering. Export the SD sequence(ref or self-contained) and then use compressor to create the DVD elements.

I don't usually do CBR unless I am having issues but many people recommend it for a number of reasons.
For less than 75 minutes on a DVD-5 I use
2 pass VBR
average of 6.5 and a max of 8(never higher)
audio:
ac3 audio at 192 and dialog normalization at -31

I have used these setting for years and in my experience have gotten great results.



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Glenn Camhi
Re: Hardware vs. Software with 1-pass CBR
on Nov 5, 2011 at 12:36:28 am

Okay, so the Sonic SD-2000 couldn't handle 23.976.

Digital Rapids doesn't seem capable of working with ProRes 4444 source material, or at least the post house we're using is having trouble with it (a gamma issue rendering a too-bright, somewhat washed out mpeg file).

What hardware encoders are typical for DVDs? I've checked with several major post houses in L.A. and so far, they all do software encodes with Digital Rapids.


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eric pautsch
Re: Hardware vs. Software with 1-pass CBR
on Nov 5, 2011 at 6:51:48 am

They dont make Hardware encoders anymore.



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Glenn Camhi
Re: Hardware vs. Software with 1-pass CBR
on Nov 5, 2011 at 7:30:40 am

So they're not in use or an advantage anymore?

Or do you just mean that new ones aren't being made because there's no need, as the specs and technology haven't changed?


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Angelo Lorenzo
Re: Hardware vs. Software with 1-pass CBR
on Nov 5, 2011 at 9:53:30 am

Just no advantage. Normal computer systems are much faster than they were in the late 90s and early 2000s so dedicated hardware was needed for workflow speed. Software implementations are better, in general, now as well.

Angelo Lorenzo
http://filmsfor.us - Helping you sell your film online






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eric pautsch
Re: Hardware vs. Software with 1-pass CBR
on Nov 5, 2011 at 1:01:05 pm

+1

....and the SD-2000 handles 23.98 fine for me. Back when I used it :)



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