"Why" use one format over another?

[Hastings]

Thank you for this forum! Although this is clearly not my area of expertise, I enjoy trying to learn it. Unfortunately, even when I try to read the newbie articles, much of it is over my head. Sorry, but I am better than I was a few months ago and I will keep reading on my own. For now though, my whole world concerning digital video ranges from capturing in .avi, converting to mpg2, editing, then converting to DVD to view. I'm only converting to mpg because I've found it takes up less space on the HD. I have read plenty on "what" the formats are (technically) and "how" to convert from one to another but I am confused as to the "why". Why would someone desire one format over another. Ok, I understand the DVD can be viewed more readily by others but besides that; is one format more desirable to edit in? Can you edit in all the formats, including DVD? Is one a better storage format than the other? I have tried to take an .avi file and convert it to mpg then to DVD, then back to mpg to edit (just as a learning experiment) and I lost alot of quality! Which then makes me think, if while half you you are switching from avi to DVD and the other half of you are switching from DVD to avi...is eveyone losing quality? And again..."why" the switching back and forth. Should I simply do all my editing before I finally move it to a DVD format. I was hoping I could share my home videos and then go back and edit later but maybe I can't.

Sorry for such a basic question but I really have done alot of reading just to get me this far (and believe it or not...its still interesting.) So as not to waste anyones time, if this can be answered by refering me to another source or article, I'll be glad to read it there rather than have someone explain it to me here.

[CWR03]

There is no "better format" in this case, because there are so many ways to perform your task, and each method will yield differing results that are subject to an individual's perception.

Every time you convert a video from one format to another (unless you use a lossless format), you lose quality. To simplify your process, don't capture in .AVI, unless you're capturing in a lossless codec such as HuffYUV. When I capture for DVD I do so in DVD-compliant MPEG-2, so I can edit the original files without re-encoding, therefore I don't lose any quality. Once I'm ready to burn those files, they're directly imported and burned without ever having been re-encoded. The only drawback is in editing - MPEG-2 can only be "cut in" on an I-frame, and they're about a half-second apart.

[Awatef]

Yeah, MPEG editing is very limited (cut and trim only afaik). But just to make things clear, DVD is MPEG! so you don't have to convert between DVD and MPEG. If you do, then you're encoding your MPEGs in a way that is not DVD-compliant.

Complex editing should always be done on high quality AVIs, say AVIs with as little compression as possible. Huffyuv, metionned by CWR, is the ideal codec since it is a lossless solution. Its drawback is very large files. The compromise is using a codec like PicVideo MJPEG. Quality 19 is good enough to preserve pristine video quality without producing too large files (you get away with about a third of what you would consume with Huffyuv).

Anyway, always keep the MPEG encoding step as the very last one. Do all your editing and then, ideally, frame-serve to the MPEG encoding software, so that you don't have to have free space for (yet another) temporary file.

[Hastings]

Thanks! Although some of what both of you said is Greek at the moment, I will read up on the content of your response so that I might ask at least an intelligent follow up question. Would either of you be able to refer me to any of this web sites FAQ's or guides (that I need to read again) or another source of inforomation, that might help me with this subject about video camera capture, edit, conversion to DVD then re-edit topic? Thanks again, I'm having fun but I don't want to be an ignorant pest to the forum members.

[Blue_MiSfit]

Here's some basic framework that I think will help. Wikipedia is a tremendous resource for figuring stuff out, especially 'big picture' stuff!

Different formats are good for different things.

DVDs are great because almost everyone has a DVD player and knows how to use it. It also generally looks great for standard definition stuff. You can't arbitrarily edit DVD content because it uses MPEG-2 with predicted frames. You can do basic editing like trimming on keyframes, which is good enough for cutting commercials, but anything more is tricky. It's also pretty big, and therefore isn't really good for archival on a hard drive.

MPEG-4 videos - usually in the AVI, MKV, or MP4 containers are great because they are small, and have great quality. Like MPEG-2, they are also tricky to edit arbitrarily because they use predicted frames to an even greater extent than MPEG-2. Also, not everybody knows what to do with an MP4 or MKV file. Set-top players are becoming more common, but its not "one size fits all" like DVD.

Lossless video, like HuffYUV, generally stored in the AVI container is awesome for a couple of reasons. Its smaller than uncompressed video, and when decoded is mathematically identical (or insanely close to it). Lossless video works with a lot of editing systems, and is an ideal capture solution because it preserves the most information, while being temporarily manageable in the size department.

There are other formats that I refer to as "acquisition formats". These are frequently tape based, like DV/DVCPRO(HD) etc... They are used in a production workflow to create content and aren't really relevant in your particular context but the same applies for them. They are generally very editable, but are pretty big and aren't ideal for distribution or long term storage on a hard drive.

The basic idea in getting the "best" quality out of your workflow is to convert between lossy formats as FEW times as possible, because every time you convert you loose SOME informatio. In other words, to preserve the best quality: (keep in mind best is a dangerous word here :)) capture into a lossless format like HuffYUV, edit however you need, and then re-encode to DVD compliant MPEG-2 if you want to make DVDs, or into MPEG-4 if you want to store the content on your hard drive.

Anyway I hope I didn't confuse you further :D

Ask questions, we're a friendly bunch!

~MiSfit

[Hastings]

Well, you certainly can't confuse me further. These responses have been helpful in that although I'm not able to simply read your comments and say "Oh, yes, of course!" but rather now I have at least a short list of "meaningful" terms that I can look up. Up to now, trying to learn this has been an exercise in "I hope I'm reading the right article" and it's only been recently that I have been able to formulate a question that needed to be asked before I could move on.

It's amazing how lost you can be outside your area of expertise, but again, I'm having fun and hope to get to know you guys better as time goes on.