AVI vs MPEG -- Which do you prefer, and when?

[Matthew Max]

I would love to hear different people's reasons for preferring avi over mpegs or vice versa in different situations.

[Chuck Engels]

In Premiere Elements it is never preferred to use MPG Matthew. That is probably the case for many editors as MPEG is a delivery format, not an editing format. There are lots of discussions here and other places about I frames and B frames...

The nature of the problem

MPEG data streams are characterized by three types of pictures:

* Intra-frame encoded (I)

I frames are independent and need no information from other pictures. They contain all the information necessary to reconstruct the picture.
* Predicted (P)

P frames contain the difference between the current frame and a previous reference I or P frame. If the earlier reference frame is removed as a consequence of editing, the P frame cannot be decoded. P frames contain about half the information of an I frame.
* Bidirectionally predicted (B)

B frames use differences between the current frame and earlier and later I or P reference frames. B frames contain about one fourth the information of an I frame.

Bidirectional coding requires that frames be sent out of display sequence to allow the decoder to reconstruct the later B frames. For display, the IPB sequence has to be rearranged in the decoder. Figure 1 on page 22 shows the relative timing of the IPB frames making up a group of pictures (GOP) at the input of the encoder, the output of the encoder and the output of the decoder. B frames need to be reordered so that future frames are available for prediction. This causes a delay.

Different applications use different GOP structures to achieve the desired compression ratio. The longer the GOP, the higher the compression ratio; hence, the long GOPs are found in MPEG-2 applications for transmission and distribution. The maximum permitted length of a GOP is 15 frames. IPB GOPs end with a B frame, which has the previous P frame and the future I frame as references. IPB GOPs are, therefore, referred to as open GOPs.

Signal manipulations of MPEG transmission streams are generally limited to switching of signal sources in a master control room and are referred to as splicing. VTR or disk server handling of MPEG production streams is referred to as editing. Editing consists of replacing a recorded sequence on tape with another sequence (clip) coming from an alternate source. The new sequence is inserted, starting with its own reference I frame substituting the original I frame. This creates a problem with IPB open GOPs. Because the B frame is the result of a forward as well as a backward prediction, substituting the I frame with a new I frame unrelated with the B frames disrupts the sequence.

Taken from http://broadcastengineering.com/mag/bro ... g_editing/

Is it possible to edit mpeg files, yes. Is it a preferred format when you have other options available, no.

[Matthew Max]

Okay, you see there? That kind of answer is EXACTLY why I am SO HAPPY to be registered member of this website. (At least I think I am...as soon as my subscription login is changed to this login.) That information explains so many things to me.

But wait a minute--Steve G. told me "for most of us veterans who edit on home computers, tape-based miniDV and HDV are our favorite formats for shooting and editing by a country mile." Some people define HDV as mpeg.

Please reconcile this for me. Then I'll have it.

[Ron]

(At least I think I am...as soon as my subscription login is changed to this login.)

Done, welcome, Matthew Max!

[Steve Grisetti]

Hi, Matthew! Glad to have you aboard!

I guess maybe it was the use of the word "mpeg" that confused people. MPEGs can be many things: Video from DVDs, low-quality VCDs, video from hard drive camcorders, video from still cameras.

Generally, just to keep things clear, we refer to standard def video from tape-based camcorders as DV-AVIs, hi-def from tape-based cams as HDV, video from AVCHD cams as AVCHD and, for most other camcorders and cameras, we refer to the camcorder model itself.

Premiere Elements 9 edits many of these formats natively. That means that it can work with each of these formats with equal success.

It can be more challenging, however, to edit, say, standard-def video from a camcorder that saves its video to a DVD or one that records standard definition video to a hard drive (both of which are also, technically, MPEGs). So, although it's possible to work with this type of video, they're not the most efficient formats to work with.

Makes sense? If not, I'll be glad to muddy the waters even more for you.

[Matthew Max]

I need to make sure I get what you are saying. The paragraph that starts with "Generally" is a little hard for me to understand. I think I just need to know a specific example or two. So look at these, please:

Sony HC9, tape-based: uploads to my computer as avi (DV) or mpeg (HDV). The mpeg in this case seems to contain more detail.

Sony XR550V: ACHDV. Doesn't hold the sudden movement well.

What in the heck am I actually working with in such cases, since terminology slides around? I really think I've just about got my brain wrapped around this whole issue...if I can get someone to iron this part out for me.

[Steve Grisetti]

Your HC9 is an HDV camcorder. It shoots hi-def (1440x1080 pixels anamorphic) on tape. When you capture this video over FireWire, the results are hi-definition MPEGs. For clarity's sake, you should always refer to this as HDV footage.

HDV camcorders can also be set to output standard def AVIs (720x480 pixels anamorphic). When you capture this over FireWire, the results are DV-AVIs. So, yes, since standard definition video has less than 1/4 the pixels of hi-def, you will definitely see more detail when you capture your video as HDV. For clarity's sake, refer to this as DV-AVI video.

Your XR550V shoots in hi-def AVCHD (1920x1080 square pixels -- which is virtually the same as 1440x1080 anamorphic). AVCHD is a highly-compressed hi-def format. Your results though should be virtually the same as you get from your HDV camcorder -- although, because it is more highly compressed, AVCHD video can require a bit more computer horsepower to edit.

[Matthew Max]

standard definition video has less than 1/4 the pixels of hi-def

Why, then, do you prefer dv avi over hi def?

At least, that seems to be the question based on all the comments I've been getting from you and others in forums. You seem to ALWAYS prefer dv avi. Yet it has fewer pixels. I know there's a detail in the explanation that will make my light bulb go on.

[Chuck Engels]

Ahhh, now I have a better idea of what you are asking

When it comes to High Definition (HDV) you don't have a lot of choices.
HDV MPEG is what Premiere Elements prefers and works best with (no rendering needed).
AVCHD is not as friendly and takes a lot more for Premiere Elements to handle.

I have a Canon HV40 and edit the HDV Mpeg files just fine. When it comes to Standard definition then I prefer the DV-AVI about anything else. When working with the HDV tape based cameras it is best to work/edit in HDV and then let the software down convert the video if burning to a DVD.

Sorry for the confusion between the SD and HDV formats.

[Matthew Max]

Yes, I've been angling in on you guys to get you to dial in on what you mean with certain words. Capture and processing and the practical concerns of which camera a one-handed shooter can use when he's moving toward and away from targets while using the other hand to manipulate items or people or balance myself while hanging over the edge of a hot air balloon--all this affects the equipment I HAVE to work with and what kind of footage I have to process afterward. It sounds like you guys want me to go back to uploading my footage the slow way, through the firewire, mini DV tape-recording with my Sony HC9, or continue with my Sony XR550V and the ACHDV, since my computer is powerful enough to handle ACHDV compression.

Right?

[Bob]

Not at all. It's YOUR choice which camera you want to use and whether you want to record in standard definition or high definition. And, it's the camera you choose which dictates how you are going to get the footage off the camera and into your computer. Tape based camcorders have to play back the recording and you capture the playback over a firewire connection. Non-tape based camcorders allow you to copy the recorded files directly from the camcorder over a usb connection or, if removable, directly from the storage media.

Are you really asking "Standard Definition vs High Definition -- Which do you prefer, and when?"

[Chuck Engels]

That is really a matter of preference, hard drive/memory camcorder vs tape based.
I definitely prefer tape and will take the time to capture the "long way" as it leads to much fewer problems on the editing end.
It is an hour well spent capturing a tape to have a worry free editing session
At least to me it is

[Matthew Max]

Are you really asking "Standard Definition vs High Definition -- Which do you prefer, and when?"

Bob, that is just what I have been wondering.

I have tons of experience with tape-based Sony HC7 and HC9 camcorders. But only recently have I been able to boil the experience down to knowledge. It has been a painful road. These cameras come with advertising and manuals that can make you think you just point and shoot and edit and poof!--you'll have what you need.

Like Chuck, I prefer the tape, and so I might go back to the tape-based HC7 and HC9 if it becomes necessary, but I will try to make this hard-drive XR550V work for a while.

I feel like I'm an inch away from understanding this topic.

[Chuck Engels]

I think that one of the primary concerns is the end result, what do you want it to be?
Is it going to be standard definition video on the internet or high definition on the internet, will you make DVDs, how about Blu Ray?
You want to stick as close as possible to the end result to avoid making unnecessary changes to the original files.

If the end result is standard definition for the web then stick with a standard definition camera that gives the best quality possible.
If you are going to 720p or greater HD, then by all means use the HDV or AVCHD camcorders and go that route

I still do think however that the HD camcorders (all types) provide excellent quality footage and even when down converted to SD the quality of the video is still better than many standard definition cameras, especially most of the consumer models. I have seen professional SD cameras produce much better quality video than the HD camcorders can produce, especially in low light. That however is generally the exception.

Camcorders and software are making huge gains and that will continue to happen. The best thing that we can all do is to test the various formats and conversions to see what works best. That is what makes this community so valuable, many of the folks here have already done the testing and can tell you what works and what doesn't

[Matthew Max]

Chuck, I make almost only wmv's (about 928 bit rate) for viewing over the web. I use 1080i.