Codecs - I'm still confused - when do they come into play?

[tmh]

I should be well past this topic...but.....still trying to "get it". I did my searches and know kinda what codecs are and are for but still some major confusion.

Are codecs only used to allow the computer to manage certain video file types or do they "do" something? I hear talk of "what codec are you using" within encoding conversations here - so do some codecs encode? Most importantly, how do I use the correct codec for the job?

A while back I was having problems opening files in VDub (I think, maybe WinDV) so i was told to install the Panasonic DV codec which I did ; problem solved. However, I really don't know where that codec gets involved with my DvAvi file - is it when i transfer from my camcorder? When I try to view it in certain apps?

Also, I know I have lots of different codecs on my system. How does any program or file know which to "pick"? Do editing and encoding programs come with their own codecs already installed? Do I need to install codecs into specific programs or just download to my computer and install as i would any program?

Thanks.

[yoda313]

Hello,

Codec
An acronym for "compression/deccompression", a codec is an algorithm or specialized computer program that encodes or reduces the number of bytes consumed by large files and programs. Files encoded with a specific codec require the same codec for decoding. Some codecs you may encounter in computer video production are Divx, MPEG-1, MPEG-2, Xivd, DV type 1 and type 2 for video and MP3 for audio.

Basically you need a codec to play back a video (any video). It's what tells the computer HOW to play it back.

When you encode you're CREATING a video. Thus you need to tell the software what instructions it needs to follow to make that file.

Kevin

[tmh]

yoda, thanks. I've read and re-read that definition many times in the past. I just don't understand why then there are so many different codecs. For example, if I transfer my DV from my camcorder to PC as an AVI file, is it by definition a DV codec? Now, lets say I encode to mpeg2 in maling a dvd; can I select a certain codec for this or does the encoder program contain the codec? Is encoding from DV to mpeg2 really a matter of changing the codec format of the video file? Is THAT what encoders actually do?

Thanks.

[yoda313]

Hello,

MPEG2 IS the dvd codec! Here:

MPEG-2
An encoding standard designed as an extension of the MPEG-1 international standard for digital compression of audio and video signals. MPEG-1 was designed to code progressively scanned video at bit rates up to about 1.5 Mbit/s for applications such as CD-i. MPEG-2 is directed at broadcast formats at higher data rates; it provides increased support for efficiently coding interlaced video, supports a wide range of bit rates and provides for multichannel surround sound coding such as PCM, Dolby Digital, DTS and MPEG audio.

Basically it is what makes up the vobs in a dvd. You capture to avi/mpeg. Then author that file into a dvd compatible structure that is the video_ts folder (which is made of up vobs {video object}, bups, ifos).

Kevin

[bazooka]

Basically you need a codec to play back a video (any video)

You also need codecs for audio.

[ZippyP.]

For example, if I transfer my DV from my camcorder to PC as an AVI file, is it by definition a DV codec?

Yes, the file was encoded by your camcorder using a dv codec. Many different types of video (and audio) can be contained inside of an avi. For example dv-avi, divx-avi, huffyuv-avi etc. All of these use different types of compression schemes, also called codecs. Some compression is more efficient so that the files are smaller, some are more "lossy" meaning that some of the information is basically discarded. Alternatively the video could actually be uncompressed which makes for very large files.

Now, lets say I encode to mpeg2 in maling a dvd; can I select a certain codec for this or does the encoder program contain the codec?

Mpeg2 is a codec so that's what gets used when maing a DVD (mpeg1 can also be used when making a DVD but that's another story). The mpeg2 codec needs to be installed on your sytem for you to be able to play it or to encode a file with it. When you install DVD playing software onto your system you usually get some type of mpeg2 codec installed as well.

Is encoding from DV to mpeg2 really a matter of changing the codec format of the video file?

Yes, in effect that is what happens. Some information is lost along the way as re-encoding will cause a quality loss to some extent. Although, if you do it right then the loss may not be noticable. You will notice that the file size gets smaller as mpeg2 is more highly compressed than DV.

Is THAT what encoders actually do?

Video encoders take one type of video and change it into another, the codecs must be installed on your sytem in order for you to access, create and play back the different types.

Hope that helps a bit.

[tmh]

Yes, that all helps. So if I now can open the pe of files i need to and can encode to mpeg2 as I need to do, then am I "all set" with regards to codecs? Or, might there be "better" ones that do similar encoding but might give me better results?

[ZippyP.]

I think you're all set.