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Forums Compression Techniques When to use one vs. two pass encoding…

  • When to use one vs. two pass encoding…

  • Steve Mac Kenzie

    April 30, 2007 at 2:45 pm

    I have been encoding video of a dynamic speaker in a convention setting that walks back and forth across the stage (so there is movement) for web use and I am wondering in general terms when one pass encoding is alright and when two pass encoding is preferable. Can anyone shed some general light on this? Will the average downloader see much of a difference if all other settings are the same?

    Thank You for your input!

  • Daniel Low

    April 30, 2007 at 4:04 pm

    Two pass (which is not to be confused with VBR, as some people do!) should nearly always give you a more efficient encode. I.E. same quality for less bandwidth or higher quality for the same bandwidth, when comparing to one pass.

    2 pass can be used with both CBR and VBR encodes.

    The only downside with two pass is that it usually takes at least double the time as the one pass and more often than not writes a temp file to disk.

    It’s a simple task to do a test on a small part of a clip to see if there’s any significant diference and quality and file size.

  • Tom Brooks

    April 30, 2007 at 5:14 pm

    Your content–a constantly moving camera shot–is the least advantageous for VBR. So 2-pass CBR would be the best choice at this point. The test will answer whether the extra pass is worthwhile for you.

  • Ed Dooley

    April 30, 2007 at 6:21 pm

    But not in Compressor (v2 at least). The only CBR setting is 1 pass (they don’t even
    name it CBR, just 1 Pass). All other options are VBR (including 1 and 2 pass).

    2 pass can be used with both CBR and VBR encodes.”

  • Steve Mac Kenzie

    April 30, 2007 at 10:11 pm

    I am currently using the adobe media encoder on this. I have done alot of editing but this is my first foray into this new adventure. I appreciate everyones help and expertise on this.

    Thank You for your input!

  • Peter dewit

    May 3, 2007 at 2:44 pm

    I would avoid using two pass on the current version of compressor. it take a insane amount fo time for long videos and honestly I think thier 2 pass looks worse than the 1 most of the time

  • Steve Mac Kenzie

    May 3, 2007 at 7:06 pm

    I am tending to agree about that, The two pass run is strictly a end of day thing because otherwise it adds up to allot of unproductive time in the middle of the day. I still have not seen any improvement either to even come close to justifying the extra time.

    Thank You for your input!

  • Daniel Low

    May 3, 2007 at 7:22 pm

    Where appropriate multi-pass encoding results in higher quality output, in software maybe it’s a luxury but using it has helped me produce higher quality that my competitors are able to. And therefore I charge much more.

  • Steve Mac Kenzie

    May 3, 2007 at 10:32 pm

    When the punishment fits the crime or for me the budget fits the work then I am all about doing every thing I can to get it as close to perfection. Right now this compression work is a bi product of my main work that is mostly volunteer and I am really only doing it now to own it in a couple months when we go back to the table for the next contract. All that being typed though I do not see much difference between the one and two pass but I have only uploaded the two pass work as I imagine on the download side there will be better performance. Any gain however marginal is a gain and I want it to be guru compatible. I imagine though that compression gurus have a system to stay productive in their work flow. It is just tough to have a long hole in the middle of the day if it is not necessary at this point. I have found that by running the encoding after hours allows me to get it done in a way that does not upset my flow.

  • Ben Waggoner

    May 5, 2007 at 8:06 pm

    What format, codec, and data rate are you targeting?

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