interesting side effect of multiple angle feature in DVDA3

bStro wrote on 4/19/2005, 11:53 AM
I was expecting the additional video tracks (aka, "angles") in DVDA3 to act like the audio tracks, where you only get one file per track. In fact, they're more like subtitle tracks -- you add files as events, which means you can put multiple files on a single track. They can even be moved and resized.

Interesting... Now, how to use this power...

Rob

Comments

JSWTS wrote on 4/19/2005, 1:38 PM
What you are noting is the difference between multi-angle and what's called mixed angle. True multi-angle would be an additional video stream that lasts as long as the first position stream. Mixed angle streams are video content in the additional video stream positions that are only different than the original video. You could have a movie that only has sections where another angle was taken, and you would only include the segments that correspond to that. It saves disc space (since you are not duplicating identical material), and allows more wiggle room for bitrate (the more video streams you have, the less 'wiggle' room you have). However, the GOP structure needs to be identical between alternative streams in these segments. Which means that you should the app take care of the segment encoding, unless you have an encoder that lets you have relatively high level control of the encode. I would assume DVDA will do this for you, but I don't know for sure. Also, if you are going to let DVDA do the encoding, it would be best to use the least compressed version of your video (ie DV for most of us), rather than having it re-encode a highly compressed mpeg file.

Jim
ScottW wrote on 4/19/2005, 1:51 PM
Jim, do you happen to remember/know if the aggregate stream still needs to stay within the 9.8Mbps/sec limit? My memory is saying that it does, but I can't find a specific reference in the Unofficial DVD Spec.

If that's the case, I think you'd most certainly want to start with DV and let DVDA handle the encode, since I'd think in most cases it would likely be forced to re-encode mpeg streams given the values most folks encode at.

I'd also think this would have some significant implications on the type of material you'd want to use for multi-angle; no fast action, etc.

--Scott
JSWTS wrote on 4/19/2005, 2:07 PM
Scott,

It's not that restrictive. You can still have fairly high bitrates with 2 angles (for each stream), but the max you can use drops as you add each stream. It's not additive across all the streams--if it was you would have some serious limitations if one used all angles available. However, it does drop off significantly as you add additional streams. I don't have my manual in front of me right now, and when I get home if the question hasn't been answered I'll post the info (along with the other rules).

Jim
JSWTS wrote on 4/19/2005, 4:16 PM
Scott,

Here's a bit more. The max bit rate for 5 angles or fewer is 8Mbps max for each video stream. For 6-8, it's 7.5 Mbps, and for 9, it's 7Mbps max for each video stream.

All GOP's should be closed.

All Streams must have the same resolution and frame rate.

With multi-angle tracks, all streams must be the same length.

With mixed-angle, all alternate streams in each mixed angle segment must be of the same length.

The length and pattern of the GOPs must be identical for all streams.

Jim
ScottW wrote on 4/19/2005, 7:49 PM
Interesting, that's a lot more flexible than I thought it would be. Thanks very much for the info!

--Scott
SonySDB wrote on 4/20/2005, 5:04 AM
I suspect you got the max bitrate values from another application as they are dependent on the implementation. Good info in general though. For DVDA, the max bitrate for 2-6 angles is 8 Mbps; and for 7-9 angles is 7.5 Mbps.

You can see these maximums by creating a video with multiple angles and by then go to the Optimize DVD dialog (File | Optimize DVD...) and selecting the video in the asset list on the left. General > Maximum bitrate shows the max bitrate based on the number of angles in the video. The highest angle bitrate must be less than the max bitrate. The highest angle bitrate is the video track with the highest bitrate plus the total audio bitrate and total subtitle bitrate.
JSWTS wrote on 4/20/2005, 6:06 AM
I did the numbers from another app (DVDSP 3). Sorry, don't have DVDA3 and or manual (but the limits were close to each other). The bottom line is that the max rates are not a reflection of the combined bitrates of all the streams.

Thanks for the clarification.

Jim