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  1. Hi there
    I think this question may have been asked before as well. I am trying to understand the bitrate/ quality issue and have couple of questions
    1. Higher the bit rate better would be quality (big size as well). However it cant be better than source video, say I am converting flv to divx/xvid then what bit rate would give almost the same quality?

    2. Am I right to assume that if I convert from h264 (Divx, Xvid) to Xvid (Divx, H264) then the selecting the same bit rate as in source file (say 800) would result in same quality?
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  2. Video Restorer lordsmurf's Avatar
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    1. Not necessarily. Encoder has large part to do with it, too.
    2. No. Different compression, different bitrate points.
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  3. converting from one type of lossy compression to another type of lossy compression will always some detail, sharpness,quality whatever bitrates you choose. It is particularly evident the more highly comp0ressed the original source is.
    h264 is another encoding algorythm that is used instead of xvid or Divx, and in general is able to attain higher levels of compression for the same level of quality as xvid/divx. Not to a fantastic level, opinions vary but from 25% to 40% smaller files CAN be achieved, using the right source material and encoding options. The price you pay for the greater/better compression is that it takes more horsepower (CPU) to both encode (a lot more) and to playback h264 video.

    800k bitrate for even SD material is very low IMO?. (double it for quality )
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  4. You will gain nothing by recompressing a lossy format.
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  5. my honest suggestion is...
    Take a nice Blue Ray DVD, Use BRip to rip it with highest possible quality,
    so you can have highest possible Quality of video source.

    Now you can start playing with various video and Audio encoders with different settings.
    And feel it, experience it, what difference you get every time.
    Experiece is The Best Teacher.
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  6. Forget bitrate unless you need files of a specific size. Use constant quality encoding instead. You will always get the quality you specify. The encoder will use whatever bitrate is necessary at each frame. With Divx/Xvid try a quantizer of 3 for watchable quality (better than most videos you may download from the web). 2 for high quality.
    Last edited by jagabo; 15th May 2010 at 20:52.
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  7. Member edDV's Avatar
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    As said, converting a lossy codec to another lossy codec will lower quality regardless of bit rate used.

    When you compare codecs, the assumption is you are using the same source file. In general the higher the quality the source file, the better the picture quality result for each codec. This is why pro camcorders use low compression (higher bit rate) codecs.
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    Originally Posted by jagabo View Post
    forget bitrate unless you need files of a specific size. Use constant quality encoding instead. You will always get the quality you specify. The encoder will use whatever bitrate is necessary at each frame. With divx/xvid try a quantizer of 3 for watchable quality (better than most videos you may download from the web). 2 for high quality.

    this!
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  9. Video Restorer lordsmurf's Avatar
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    Originally Posted by edDV View Post
    As said, converting a lossy codec to another lossy codec will lower quality regardless of bit rate used.
    .
    That's just dogma -- it's not really true. Between filtering and good bitrate allocation, you can improve quality, even between lossy codecs.
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  10. Member edDV's Avatar
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    Originally Posted by lordsmurf View Post
    Originally Posted by edDV View Post
    As said, converting a lossy codec to another lossy codec will lower quality regardless of bit rate used.
    .
    That's just dogma -- it's not really true. Between filtering and good bitrate allocation, you can improve quality, even between lossy codecs.
    It all depends on codec and bitrate for the source vs destination. Filtering adds other issues. It would be a rare case where lossy codec conversion at equal input to output bit rate would maintain quality.

    Basic rule is to acquire with lowest compression and save high compression for final distribution.
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  11. Video Restorer lordsmurf's Avatar
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    It really depends on the content, the software, and the experience/knowledge of the user.
    I'd suggest most people would just screw it up more, hence the dogma.
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  12. Member Marvingj's Avatar
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    I agreed with Lord smurf...............experience plays a great part...
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  13. Member edDV's Avatar
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    So give examples.
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  14. Member
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    Hopefully not hi jacking this tread, is there a calculator or calculation I can work with for a Bluray to dual layer DVD compression exercise?
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    Still that simple...I have used these calculations for DVD work for years...Cheers.
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    The problem is, when you author, the transport stream container takes up an extra ~7-8% overhead over the raw streams

    To get a more accurate picture, I would use a bitrate calculator specifically for this. The author of avchdcoder has such a tool.

    http://tools.twanwintjes.nl/index.php?page=avchdcalc
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  17. He said he's making DVDs so I assumed he meant regular MPEG 2 movie DVDs, not AVCHD discs.
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    Thanks to all....God I love this group of talented people....
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  19. Member yoda313's Avatar
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    One thing to consider is if you take a low quality source, like a flv for example, you know what quality you have to start with. I have recently taken to converting flv to psp and dvd and they haven't turned out too bad.

    Now qranted I know that flv is not the best source. But when you have realistic expectations you can get decent results.

    I know I have even taken divx or xvid and converted to 320x240 wmv for zune playback and have gotten adequate results.

    I'd say its all in expecations. Yes you can't get better quality than you start with but what you end up with can be watchable (again its all dependent on user expectation, encoders used, playback equipment, and of course the final resolution encoded to and the size and resolution of the playback screen).

    I'm not saying taking an flv and making a full fledged dvd out of it makes sense to a lot of people but if all you want to do is watch it some other place than on a computer screen the conversion is worthwhile. I always say as long as you don't expect much you'll be pleasantly surprised with the results.
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    Sure, a low bitrate, low resolution file will look OK on a 4"x3" screen but try viewing it on anything bigger and it looks like crap.

    People say that the low bitrate DivX and XviD files that they download and burn to disc look good on their LCD TVs but their viewing taste is a lot lower than mine and I don't watch Blu Ray.

    A SD DivX or XviD with a bitrate under 2000kb/s is unacceptable to me for watching on my 42" LCD and some of the higher bitrate files are still blotchy in dark scenes. If you have the patience to encode high quality H264 and a player to play them then that's the way to go.

    As for DVDs, IMO, it makes no since to burn to DVDs anymore when you can store everything on thumb drives and external hard drives and play on a hardware media player like the WDTV.
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