Why are my MPEG2-DVD files so large?

[Marc Walker]

I don’t need an answer now, so how do I delete this question?

[Marc Walker]

It was pretty obvious really, I wasn’t paying enough attention to the information in front of me (I was pretty tired at the time).
The HD files are AVC/AAC streams, with an average total bitrate of 5,066kbps.

As it turned out, the settings I was using in AME (min: 2.8, Target: 5, Max: 7) Created a video file with a very similar bitrate (5Mbps or 5,000kbps).

What confused me was how a HD format and a SD format could be so similar in size, but not in quality, but there it is. They were. I think this is because the AVC/H.264 compression has a better result than MPEG2.

Further:
When I played around with the MPEG2-DVD settings, I found that I could lower the target bitrate to 3 or even 2Mbps, and with 2-pass and max render quality enabled, there was very little noticeable degradation.

To help me further refine my bitrate settings, I searched for a tool to help me figure out the optimum bitrate to get decent quality while bit-budgeting for DVD. I have 8 HD files at 55mins to 1½hrs each, and I don’t want to use 8 discs.
I found a very detailed and easy-to-use bit-budgeting calculator, which helped my fit two files onto each disc with optimal settings.

[Jeff Pulera]

Hi Marc,

Looks like you answered your own question for the most part. Most HD cameras recording as AVCHD record at 24mbps, and some might go a little higher and some may have a 17mbps mode, but nothing lower typically. So in that case, yes the MPEG-2 DVD files should be much smaller. However, I don’t know where you got your HD files, but they were already pretty compressed, which is why the file size was about the same.

You are correct that H.264 is a much more efficient codec than MPEG-2, meaning you can push the data rate lower and still maintain decent quality.

What type of content is in your video? If it’s a talking head shot, like a speaker at a conference with very little movement in the picture, then you can get away with really dropping the DVD data rate. However, if there is a lot of movement in the image then it can quickly degrade at low bitrates. I usually don’t go below the 4 to 4.5 area myself (2+ hours), but did do a 3-hour talking head video once and it looked just fine!

You’re using the same calculator I do, works well.

Thanks

Jeff Pulera
Safe Harbor Computers

[Marc Walker]

Hi Jeff, thanks for the reply,
Yeah, I just did a g-search for calc, it’s really useful.
The HD files were FLVs originally, which were being streamed on the internet by a well-known broadcaster. They are live band performances, so I suppose they are in the middle of the ‘detail and movement scale’.

I guessed they were quite compressed after I figured the above out, I’m an audio guy, not a video guy, so I get stuck with video processing, but the FLV files looked decent enough, the only problem with quality (apart from this problem) was when I watched the DVD, I could see like pretty large sharpness-type artifacts, which disappeared when I adjusted the sharpness along with the contrast on the TV, which I didn’t really want to do as other DVDs were fine (and the artifacts aren’t there on PC), but it still looked pretty good anyway. Would turning ‘Max Depth’ on in AME help with this?

But I’m pretty happy overall with bitrate/quality ratio anyway because it’s not a professional job like. I just wish I could get a straight answer for my other DVD-related problem.

Anyway, I appreciate your insight.
Marc

[Jeff Pulera]

“an AVI file format is about 700MB for a normal length movie of an hour and a half.”

The above is from the link you provided. I’m trying to figure out – on what planet would a 90-minute .avi be only 700mb? That is funny!

Seriously, all I can think is that perhaps the article is so old that they are talking about the “postage stamp-sized” videos from the olden days. They never mentioned the resolution. Certainly not talking about SD video. So please, do not let that article influence your thoughts, it is way off base to anything modern.

Thanks

Jeff