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Compression

ralph01ralph01 Posts: 0
edited December 1969 in Technical Help (nuts n bolts)

Something that is still a total mystery to me is compression.
I render an animation and save as .avi and it looks great, but a 1 minute video is several hundred megabytes. When I convert to .wmv so I can post somewhere the size drops but quality also drops considerably. Same problem with a still image. When I convert from .bmp to .jpg it looks like crap.
How do others make files a reasonable size but keep them high resolution? I'm sure it's something simple I'm missing.

Comments

  • SpottedKittySpottedKitty Posts: 7,232
    edited June 2013

    ralph01 said:
    Same problem with a still image. When I convert from .bmp to .jpg it looks like crap.

    It sounds like your jpg save option is set to "insanely high, no-one ever uses this" compression level. You can change this. It varies from program to program, but usually there's a drop-down compression option as part of the save dialog, or else an "options" button, where you can set it to whatever you want. Experiment, then decide what trade-off between file size and image quality you're prepared to accept. (FWIW, I always change to jpg as part of postwork, all my raw renders are saved as tiff.) Something similar may be happening to your movie conversions.
    Post edited by SpottedKitty on
  • JaderailJaderail Posts: 0
    edited December 1969

    Nods vigorously!! There is a very fine line between compression and quality in jpg and ALL video save formats.

  • MattymanxMattymanx Posts: 6,879
    edited December 1969

    https://en.wikipedia.org/wiki/Data_compression

  • Takeo.KenseiTakeo.Kensei Posts: 1,303
    edited December 1969

    Render directely in JPG or PNG for still images. Why doing twice the job by reconverting a BMP?

    For movies, It won't be as simple as that but my first advice would be not to render as avi. I didn't see any options for compression in DS and didn't bother trying cause I like to have control
    Render an image sequence (jpg). Doing it this way will give you the ability to postprocess your render and if your computer crash you won't lose everything and can just render the missing images

    Once you rendered your images you could use some cool tool like VirtualDub (http://www.virtualdub.org/) which can take an image sequence and make a movie with it. To compress the movie you just have to tell the software to use a codec (see http://en.wikipedia.org/wiki/Codec). There are some free codecs like x264vfw (http://sourceforge.net/projects/x264vfw/) that can give you quality and compression control but you have to learn how all of these work.

    There are certainly other tools free and not free but that's what I would use

  • ralph01ralph01 Posts: 0
    edited June 2013

    Thanks for the replies.

    After this advice I have been experimenting with render settings and now see how to render as a jpg. Never looked closely enough at render options but now I see it. For stills I was just rendering as a movie with start and end frame the same (duh). Makes a big difference.
    Not sure how to make a movie from a jpg sequence though but will play around with it some more. I do already use virtualdub for editing.

    Thanks again.

    Post edited by ralph01 on
  • JaderailJaderail Posts: 0
    edited June 2013

    ralph01 said:
    Thanks for the replies.

    After this advice I have been experimenting with render settings and now see how to render as a jpg. Never looked closely enough at render options but now I see it. For stills I was just rendering as a movie with start and end frame the same (duh). Makes a big difference.
    Not sure how to make a movie from a jpg sequence though but will play around with it some more. I do already use virtualdub for editing.

    Thanks again.

    I use VeDub myself, just render the movie to frames then load them all with select all in VeDub. Or load sequence both work well.
    Post edited by Jaderail on
  • SpottedKittySpottedKitty Posts: 7,232
    edited December 1969

    Takeo.Kensei said:
    Render directely in JPG or PNG for still images. Why doing twice the job by reconverting a BMP?

    The most important thing to consider here is how jpg compression works — it throws away "unnoticed" detail in the image. Every time you re-save the image. This isn't a problem if you're never going to be doing any postwork, but re-resaving a jpg is the best and quickest method known to wreck the image quality.

    As an aside, this is also why jpg works better in some kinds of pic than in others — it was originally designed to be used on scans of photographs (or digital photos) with lots of tonal range and lots of intermediate shades. Any other kind of image will quickly show the kinds of artifacts (blurs, squares, etc.) we're all familiar with from badly compressed YouTube movies.

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