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With the basic idea i have about video formats, i always thought FLV offers the lowest quality & hence smallest file size but this particular page made me confused. http://blip.tv/file/2932017

If you expand the "Files & Links" & "Metadata" blocks in the right-side bar, the flash file size is bigger than other 2 mp4 / m4v files.[there is significant difference in size]

Does it mean in this particular case the FLV file will have better quality?

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See this slightly similar question: superuser.com/questions/28225/… –  Sasha Chedygov Dec 8 '09 at 6:16

3 Answers 3

Video File size has do to with a number of factors, not just video quality. Frame resolution (720p, 720i, 1080p, 1080i) Audio bit rate (256kbps, for example) Video bit rate (no example, sorry!)

Flash has always been known for its exemplary file sizes and decent quality. I don't know for sure which one is better though.

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"videoquality" is another expression for "amount of information per pixel". assuming you have a "normal" pixel consisting of RedGreenBlue (rgb, video is normally stored in YUV) you have 24bits of information for that pixel. the difference between the codecs used to store and restore that information can be a multitude of:

  • speeded needed to encode or decode
  • used storage for the encoded video
  • used ram while encoding / decoding
  • etc etc etc.

if you tell a lossy encoder to encode a pixel with 1 bit per pixel, then depending on the used codec AND the content you might get pretty crappy video. but it could also look pretty fine (lets say for a black/white image without lots of movement). as long as the decoder gets close to the original amount of information you will experience a high quality video.

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The distinction between video container and codec is important to understand:

The container format specifies the types of data within and the way it is stored, but not specifics on how to view the individual streams. See also Comparison of container formats. That is where video codecs come in, which are often confused for containers themselves.

A video codec is a way of compressing and decompressing digital video so that the overall file size is smaller than the original uncompressed video. Most video codecs use lossy compression; meaning that after uncompression, the video has lost some of its original quality. Although there are lossless video codecs such as HuffYUV and Lagaraith, they are much less common as some quality loss is generally accepted for having more manageable files.

Each codec has its own particularity: Some result in better compression, some in better quality, others are better at encoding transitions (when the video films rapid movements).

Flash Video is a container file format used to deliver video over the Internet. Though the Flash Video container format itself is open, the codecs used with it are patented. The most recent public releases of Flash Player also support H.264 video and HE-AAC audio.

Therefore, FLV files by themselves do not assure better video quality. An FLV file containing H.264 video will have, when comparing with AVI, the same quality and a comparable file size. However, you'll find that more players know how to play AVI format than FLV.

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