AVI vs MPEG2

[jmsrickland]

Is AVI better quality than MPEG2 or is this a meaningless question?

[edDV]

Is AVI better quality than MPEG2 or is this a meaningless question?

"AVI" can cover anything from uncompressed 4:4:4 RGB, to DV, to Divx to one flashing pixel. MPeg2 can cover anything from 1080p HD masters to something like vcd. So yes, the question is mostly unanswerable.

[jman98]

It's actually a good question, it's just a little hard to answer. I suppose a simple answer would be that AVI is neither better nor worse than MPEG2, but depending on the codec used for the AVI and the bitrate and resolution, one might give better results than another. For example, I would expect an AVI using Xvid/Divx to look better at a bit rate of 2000 than MPEG-2 for the same resolution. MPEG2 generally will require higher bit rates to get the same quality as certain codecs that can be used with AVI.

It's kind of like comparing apples and oranges though as MPEG2 is a codec and AVI is not. AVI is a container.

[kschang]

AVI is a container, not a codec, where MPEG2 is a codec (and a container). So comparing the two is not valid.

[jmsrickland]

So by the definition of "container" can I conclude that it is raw audio/video data inside an AVI file?

Are these "codec" like little code files, maybe similar to a DLL that does the actual encoding and/or compression/decompression stuff? How do authoring software know which codec to us, do thy scan your system and find the correct one?

[solarfox]

So by the definition of "container" can I conclude that it is raw audio/video data inside an AVI file?

Something like that. An AVI does consist of chunks of audio and video data, yes, but not necessarily "raw" data. (In computer jargon, "raw data" usually implies "uncompressed" or "unprocessed.") While an AVI can contain raw uncompressed data, it more usually contains compressed audio and/or video, along with information on which codec(s) were used.

Are these "codec" like little code files, maybe similar to a DLL that does the actual encoding and/or compression/decompression stuff?

Pretty much, yes. A "codec" (enCOder/DECoder) is a DLL or driver file which the OS uses to process the audio or video data.

How do authoring software know which codec to us, do thy scan your system and find the correct one?

Typically, you only have one codec for each format type installed -- one to handle MPEG2, one to handle DivX, one to handle AC3, one to handle Quicktime, etc -- and so the authoring program chooses based on which codec is available to handle the type of compression you've told it to save the files in.

[kschang]

In case of duplicate codecs, or multiple decoders for same stream type, Windows use "merit system" to determine who gets dibs on encoding/decoding the file. You can adjust this with something like DXMAN or DSFM

The container would have a 4cc code (4 letter code usually) that will tell the file reader what sort of codec the chunks following would be using.

[jmsrickland]

In case of duplicate codecs, or multiple decoders for same stream type, Windows use "merit system" to determine who gets dibs on encoding/decoding the file.

So if a particular "codecs" deals with a particular encode/decode scheme and I may have more than one of these in my system and Windows determines which one is going to do the job and of the several that I have can one do a better job than another? If so, then it is possible that the one that was selected could be the one that does not do as good of a job as one of the others, correct?

you can adjust this with something like DXMAN or DSFM

Does this mean I can force which "codecs" to use? If so, then is this primarly a matter of one's knowledge as to which "codecs" would be the best choise?

The container would have a 4cc code (4 letter code usually) that will tell the file reader what sort of codec the chunks following would be using.

So this code which is in the audio/video file says what type of "codecs" to use but not which one if I have more than one?

[kschang]

In case of duplicate codecs, or multiple decoders for same stream type, Windows use "merit system" to determine who gets dibs on encoding/decoding the file.

So if a particular "codecs" deals with a particular encode/decode scheme and I may have more than one of these in my system and Windows determines which one is going to do the job and of the several that I have can one do a better job than another? If so, then it is possible that the one that was selected could be the one that does not do as good of a job as one of the others, correct?

Yes

you can adjust this with something like DXMAN or DSFM

Does this mean I can force which "codecs" to use? If so, then is this primarly a matter of one's knowledge as to which "codecs" would be the best choise?

Yes. That's why there ARE such tools.

The container would have a 4cc code (4 letter code usually) that will tell the file reader what sort of codec the chunks following would be using.

So this code which is in the audio/video file says what type of "codecs" to use but not which one if I have more than one?

Yes. Download DXMan and try it yourself. Don't change anything though. This can seriously affect your ability to play the files. It is quite possible to screw it up completely that you can't play ****.