File types, video formats, and codecs!!!

[mkenyon2]

This is a little post to help people who are scratching their heads, trying to sort out the whole format/file type thing.

I found this section on the MEncoder site:
http://www.mplayerhq.hu/DOCS/HTML/en/containers.html

Note what they say:

It is important to clarify a common mistake. When people see a file with a .AVI extension, they immediately conclude that it is not an MPEG file. That is not true. At least not entirely. Contrary to popular belief such a file can contain MPEG-1 video.

You see, a codec is not the same as a container format. Examples of video codecs are: MPEG-1, MPEG-2, MPEG-4 (DivX), Indeo5, 3ivx. Examples of container formats are: MPG, AVI, ASF.

video formats
The next page in that section talks a bit about video formats.
http://www.mplayerhq.hu/DOCS/HTML/en/video-formats.html

Here is a sum-up of what I gleaned:
MPEG format: (MPEG1 and MPEG2) Not very compressed, but good for streaming. (Because you can lose a frame and just pick up with a new one.)

AVI format (Divx and Divx4 as well as others) Better compression, not so good for streaming. Interleaved (where video and audio are mixed together) is better than non.

Codecs
Video formats are then filled with Codecs. (MPEG2, Divx, H.264 can be read about here...
http://www.mplayerhq.hu/DOCS/HTML/en/video-codecs.html
Mpeg2 (What most video capture with onboard encoders use) seems to have low compression, but also very low CPU loads.
Divx seems to have the best compression (smaller file size) to CPU decoding ratio.
H.264 seems to have the best compression, but usually heavy loads on the CPU.

En/De coding
So... you've seen encoding and decoding... what does it mean?
Encoding - Taking video (from one source) and converting/compressing/whatever into a file/format using a codec.
Decoding - Reading the video from the file using the codec.

So, when looking for an encoder/decoder setup, you need to find a decoder that will decode (read) the files as they are encoded by your setup.
What you're looking at is Intervideo, FFMpeg, or others. This is software that looks at your video file, and selects/uses the codec to decode the file.
For instance, FFMpeg 'includes libavcodec, an audio/video codec library'

That's decoding.

Encoding is again with software, such as MEncoder, which uses codecs to encode or create your video files. One note, video capture cards often come with a hardware (chip) encoder that takes your video signal, and gives a stream to your computer which is then stored as a file, needing very little from your computer for the encoding.

I'd like to get Sub to fill me in a bit better on where VMR9, EVER, and Overlay Manager fit it. My understanding is that these are systems used by your computer to put the decoding images on your screen.

Hopefully this helps.

Edit: One thing to note, your PC can play anything you have a decoder and codec for. However, set-top devices (Like the MediaMVP) are sometimes limited in the codecs they can decode.

Edit: Found this info about Divx vs Xvid:

Yes, Divx includes some scaling, noise reduction, and deinterlacing options in their encoder. Xvid does not. Divx is faster than Xvid at similar settings. But Xvid is slightly higher quality and gives you finer control. Pick whichever suits you.

It seems that Divx is commercial, where-as Xvid, it's main/direct competitor is Open Source.

[mkenyon2]

The reason I dug into this was because I was transcoding my recordings from TV into .avi files to save space, and remove permanently the commercials.

With the above info in mind, I have decided to go with these settings in Stattik's SkipTool.

xvid/mpeg2 2pass
Yes IVTC
Automatic scaling

This may take longer than it had been, but should be better quality.

[Deusxmachina]

I don't understand the "xvid/mpeg2" part. I assume anything you wouldn't want to more easily put on DVD would all be xvid.

Anyway, mainly wanted to say there is little reason to use 2-pass unless wanting a very exact file size. Constant Quality will be twice as fast and will have, um, a constant quality for every frame.

Unless someone is thinking ahead to want to know ahead of time that, say, 24 episodes of a TV show will all for certain fit on one DVD after they've re-encoded them all, 2-pass doesn't hold a lot of value. Doubling the encoding time aside, the same file size of those episodes are likely to look worse on average in 2-pass since episodes that didn't need the extra size used it anyway, and episodes that do need the extra size have a capped limit.

Plus, with CQ you set it and forget it, whereas 2-pass needs to be changed based on the length and action and resolution of the show.

[mkenyon2]

Well, episodes, if you did them all at once, maybe. But I don't know that I'd ever do all my episodes with the same setting.