Compatibility and standards regarding bitrates and audio.

[PuzZLeR]

I hear alot of talk about things being "non-DVD standard" or "it won't work for all DVD players", etc, etc.

I know that aspect ratio, resolution, etc, should be a certain type for the formats to work.

Can anybody tell me about bitrates? If I use the right specifics for size (aspect ratio, resolution) will changing the bitrate have an effect on compatibility?

In other words, resolution has several standard pixel combinations and apect ratio has two standards that I know about: 4:3 and 16:9 for machines to accept it. Is there a bitrate "standard" also?

As well, I'm also concerned about audio. Do you recommend LPCM or AC3 or MPG Layer2 as the standard (if there's a standard)? Would all DVDs be in AC3 if it wasn't for a royalty fee paid to the Dolby group?

Anything else that needs standardizing?

I am not asking about quality or file size. I understand all that. I am concerned about compatibility now, and in the future, with lasting memories that I have archived.

I want to keep this stuff for a long time (such as big family events for the future generations) and want to be able to use it widely. I also do understand that technology happens, but the closer you are to the older "standards" the more likely the next generation formats will accept it or convert it. I don't want to have to keep re-encoding video down to mud because of "incompatible formats".

Thanks in advance!

[guns1inger]

Start by reading What is DVD (top left corner). this will give you the basics. The DVD standards set out what is and is not compliant.

DVD has a maximum combined bitrate of 10080kbps, up 9800kbps of which can be video. For commercial discs this fine, and a player must be able to sustain this to carry the DVD logo. For burned discs, because of the vaguaries of materials used, surface readability, burning quality etc. the maximum bitrate may be somewhat less.

There are also some reports of very low bitrates causing problems for some players, although the theoretical minimum is 0kbps.

Encoding can also use either a constant or variable bitrate. Neither is more or less compatible than the other, so long as it remains within compliant levels.

LPCM, AC3 and DTS are all part of the standard. AC3 must be able to be downmixed to stereo analogue output. Mpeg1-layer2 is part of the PAL spec, but is now supported by many NTSC players. There is not guarantee that it will play however. DTS is optional, and connot be the only audio track on a disc because downmixing to analogue outputs is not part of the spec for DTS.

LPCM is usually reserved for music discs because of the high bitrate and the amount of space it requires. It is very rare nowadays to find a new movie release that does not use AC3 for encoding as a minimum. Even Dolby ProLogic tracks are encoded as two channel AC3 for authoring.

If you observe the resolution, framerate and bitrates of the specs, then you should produce compliant source material. That does not guarantee you get a universally playable disc.

You also need to make sure you use certified software for encoding of video and audio, and standards complaint authoring software. You need to make sure you use a good burning application, and only burn to good quality blanks.

Will all this guarantee you will get a universally playable disc ? Nope. But it will give you the best odds.

[Bjs]

Some goldies to follow :

1: Some players have issue with playback of mp2 audio .

2: FORGET variable audio ... if you want to re-encode later to another format ... you will get a big headache .

3: Ac3 allow's you to fit more content ... so forget lpcm , and the mp2 headache .

4: Bitrate never below 64kpbs for ac3 audio ... in many cases , audio cannot be heard in playback .

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5: Use quality disc's ... verbatim's work well ... tdk went to hell fast with outsourcing .

6: For dvd-r , dont burn more than 4.3gig ... best compatability .

7: Burn as slow as possible will provide better fixation of data to media ... they'll last longer if stored well .

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Stick with these should keep most out of trouble .

8: Know your aspect's .
9: Format's .
10: Framerate's .

[PuzZLeR]

Fabulous responses folks. I'm impressed. I read and reread the "What is DVD" as well and it all makes sense.

Just one more question regarding all this.

What's the deal with this interlaced/non interlaced stuff?
What's the deal with the frame type being lower frame first or upper frame first or frame based?

Ok, that's two questions, but I'm really asking only one thing. I don't really care to understand them right now, just what their role, if any, is with regards to DVD compliance.

Thanks in advance!

[guns1inger]

Interlaced video displays a frame in two passes, called fields. Each field consists of every second line of video. Two fields make up a frame, so if the framerate is 25 frames per second (PAL) then an interlaced PAL video displays 50 fields per second. NTSC works the same.

Top Field First and Bottom Field First describe the field order. TFF means the field with the first scanline is displayed first. BFF means the field that starts with the second scanline displays first.

Progressive, or non-interlaced, video means that the entire frame is displayed in a single pass.

[PuzZLeR]

Thanks for the answer. However, how do they all relate to DVD compliance?

For example is BFF more compliant than TFF? Are they an issue at all?

[guns1inger]

DVD can be either. What you use depends on your source. Interlaced DV, for instance, is bottom field first, and so should be encoded that way. Many analogue capture cards capture top field first, and so should be encoded TFF. Reversing the field order will result in strange artifacts and jerky movement. If you get them the wrong way around, you will soon know it.

Both are compliant, as is progressive material.

Most movies encoded for NTSC DVD are progressively encoded at 23.976 fps, with 2:3 pulldown flags applied for TV playback.

Most PAL material is interlaced, however if it comes from a progressive source the field will come from a progressive frame. This means they can be combined into progressive frames for, say, divx encoding without getting artifacts.

Video shot in an interlaced manner will have slight changes between field during movement. This creates the combing effect you see on your PC monitor during playback. Your DVD player and TV take care of this for you, so you don't see it during playback. The playback equipment is to efficient at this that you are always better off leaving interlaced material interlaced, even if playing back to a progressive TV display.