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Old 2008-01-04, 18:03   Link #1
ApostleOfGod
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What's the difference..?

What's the difference between XviD and H.264? I tried Wiki and I don't know much about softwares or programs or technology in general, so I was only able to pick up the fact that they are both related to MPEG -_-...

Can someone tell me the difference between these two?
Thanks in advance,
-A.K.
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Old 2008-01-04, 18:31   Link #2
Lanner Falcon
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MPEG -4 is a standard for various types of audio/video codecs. It has several parts. Xvid relies upon an older part of the MPEG -4 specifications, thus the lower quality.

Xvid is written using MPEG-4 libraries (standards, if you will), while H.264 is one of the official MPEG -4 suite encoding standards, each of which may encompass a variable amount of codecs.

Thus there are different types of codecs that rely on the H.264 encoding. Xvid is not among these, it uses a different MPEG -4 standard (ASP) , which explains the difference in quality between it, and codecs that use H.264 (i.e. the Quicktime Codec).

Here are some examples: Standard: MPEG -4/MPEG -3, Codec: H.264/ASP, format: mkv/avi. (Xvid only works for avi)

Those aren't all of course, but basically any video file you watch falls under first a specification, then one of the codecs based of it, and then a format. (For instance mkv is a container format, and avi is just a single file.).

To play a file you need to have the codec it was written in, and a player that supports the format. Don't worry about the specifications

All this leads to the conclusion that Xvid encoding has less quality, greater support, and larger file size, while things written to the H.264 (or MPEG -4 part 10, if you will ) specification have greater quality, less support, and smaller file size.

Hope I've helped a little.

Last edited by Lanner Falcon; 2008-01-04 at 19:29. Reason: Clarity
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Old 2008-01-04, 18:48   Link #3
anime_layer
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Short answer:

XviD = Older, good quality, wide support on software players and hardware devices and fast playback

h264 = Newer, better quality, limited support and slower playback


Long answer:

In this case, with XviD you mean MPEG4 part 2 or MPEG4 SP/ASP
and with h.264 you mean MPEG4 part 10 or AVC/h.264.
Both belong to the same set of standards (MPEG4) but are not otherwise directly related.

MPEG4 is a video standard that defines how a compressed video file is played back (decoded). It doesn't define how the video is compressed (encoded) but rather leaves that part purposely open to allow many competing encoders and improvements in compression quality even after the standard has been set.

MPEG4 part 2 SP/ASP is generally referred to as only MPEG4. As I said above, the standard defines how the video is being played back. This means that any MPEG4 SP/ASP video can be played with any MPEG4 SP/ASP video decoder. Usually, everyone who makes an encoder to create MPEG4 videos also makes an decoder but they are not necessarily directly connected. Any movie from any MPEG4 SP/ASP encoder should play with any MPEG4 SP/ASP decoder.

Popular MPEG4 SP/ASP encoders are DivX, XviD and libavcodec. Those names actually only say how the video was made. They don't mean that their decoder has to be used for playback. The videos they generate are usually standard MPEG4 SP/ASP and play back on any standard decoder.

MPEG4 part 10 AVC/h.264 is basically the same but 5 years newer. It allows better compression i.e. smaller files with higher quality. This comes with the downside that more processing power is needed to play MPEG4 AVC/h.264 and that it's not as widely supported as MPEG4 part 2 (for now).

Popular encoders for MPEG4 AVC/h.264 are x264, mainconcept and nero digital. Again, they are needed for compression, the resulting video plays back with any MPEG4 AVC/h.264 compliant decoder.

PS: Both DivX and XviD created unofficial extensions to the MPEG4 SP/ASP standard. DivX introduced GMC and XviD QPel to improve quality but break standard with regular MPEG4 SP/ASP decoders. Videos that use GMC or QPel can cause problems especially on hardware players that closely rely on the official standard. AFAIK neither GMC nor QPel are used toaday anymore.
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Old 2008-01-04, 20:19   Link #4
ApostleOfGod
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Wow, that's a lot of information for me, so it might take a while for me to realize more, but I get partly the point and what I pretty much needed to know, thanks to you two.

Just one more question though..

If h.264 is higher quality (HD) and smaller file size, how come the torrents for h.264 are bigger than XviD torrents? Sorry if it's a dumb question, but it doesn't make sense for me.

Thanks again,
-A.K.
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One is to live life as if nothing is a miracle.

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Old 2008-01-04, 20:44   Link #5
arenine
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For equivalent quality, the h.264 will be of a smaller file size. But most of the h.264 torrents you see are of higher resolution than their XviD counterparts. Higher resolution means that the picture is bigger and has more detail so a bigger picture naturally has a larger file size. If video is just a series of pictures, those small differences just adds up resulting in the size difference.
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Old 2008-01-04, 21:29   Link #6
Lanner Falcon
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Information Confirmed

Quote:
Originally Posted by arenine View Post
For equivalent quality, the h.264 will be of a smaller file size. But most of the h.264 torrents you see are of higher resolution than their XviD counterparts. Higher resolution means that the picture is bigger and has more detail so a bigger picture naturally has a larger file size. If video is just a series of pictures, those small differences just adds up resulting in the size difference.
This is accurate. But this is also because so much of the actual quality is lost in the conversion of a RAW to a say… a subbed avi in ASP, that the immense amount of extra quality you didn't lose in the conversion to H.264 makes this version larger. (more quality = greater file size). So at times it doesn't even have much to do with resolution. (though I'll repeat again: He is generally correct.)

And the sub groups are fine with it this way, partially for reasons of accessibility. In other words, the larger file size is still manageable in their minds.

I've even seen H.264 files that were of seemingly lower quality than an equivalently sized avi's, until I realized that they both came from the same, LQ RAW; I discovered that because of the lack of some of the pixels, the avi version looked a little less blurred, and a thus a little more clear. Absolutely speaking the H.264 mkv version was better quality, even then.

Last edited by Lanner Falcon; 2008-01-04 at 21:38. Reason: Clarity
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