We've had some discussions about VMS bit rates in other threads, and I finally found some time to do a little test.
In VMS (Vegas Movie Studio), we have limited options for rendering to MPEG2 (for DVD) from within VMS. Basically, we can chose from two different predefined, "blackbox" templates -- neither of which specifies the target bitrate, etc. However, if rendered in VMS to DV-AVI and passed on to DVD Architect Studio, we then have the option there to specify a bitrate, or to select "fit to disc" when rendering to MPEG2.
The basic question has been "how good is the VMS render to MPEG2, compared to the slower, two-step process (render to DV AVI in VMS, then render to MPEG2 in DVDAS)".
I started with a 3 minute long test project. This is the project I do all my "experimenting" in. Play around with chromakey effects. Experiment with track motion. Learn pan-crop keyframes with some big, still photos, etc. Multiple layers, effects, etc. I should have used just a simple video of my kids running around or something -- it would have been
much quicker to render.
OPTION 1: In VMS, click "Make Movie", select "Burn it to DVD".
This option creates two files, "Test-VMS6.mpg" and "Test-VMS6.wav". This took 22 minutes to render just the 124MB mpg file. (Audio file -- 32.9 MB .wav file -- was then rendered very quickly after the video was done.)
OPTION 2: In VMS, click "Make Movie", select "Save it to your hard drive", then select "MainConcept MPEG-2", with the "DVD Architect NTSC Video Stream" template. This also took about 22 minutes to render just the 124MB mpg file. (This option does nothing for audio. Creating the audio file would require another manual operation.)
OPTION 3: In VMS, click "Make Movie", select "Save it to your hard drive", then select "Advanced", "Video for Windows AVI", "NTSC DV Template". This took about 21 minutes to render a 652MB AVI video file, which includes the sound stream. Opened DVDAS, brought the AVI file into the project, then rendered AVI to MPEG-2 using a default bit rate of 8.000 Mbps. Took about 4 minutes 30 seconds to render from AVI to a 178MB VTS_01_1.VOB MPEG-2 file (includes audio).
Using the freeware version of the "Bitrate Viewer" that I just discovered mentioned in another CamcorderInfo.com forum, I determined the following results
(Viewer available at
http://www.tecoltd.com/bitratev.htm)
First of all, all three options produced a video stream described as "MPEG-2 MP@ML VBR". I assume this means we get a Variable Bit Rate. Does this also suggest that the results below -- especially the average values, might be highly dependent on the content of the video -- ie how much motion there is, how many scene changes, etc.? I'm thinking, but I'm not sure, that the resulting average bit rate in VBR could end up low because it really didn't need any more data to render a scene with little motion in it (ie slow pans on a still photo).
Also, all three were the same in other, not-understood-by-me aspects: DCT Precision = 9, QuantScale = nonlinear, VBV buffer size = 112, etc.
OPTION 1: "Burn it to DVD"
Peak Bitrate = 7685. Avg Bitrate = 5382.
Peak Q.Level = 20.05. Avg Q.Level = 6.40.
OPTION 2: "Save to hard drive" "MPEG-2" "DVDA NTSC" template
Peak Bitrate = 7685. Avg Bitrate = 5382.
Peak Q.Level = 20.10. Avg Q.Level = 6.40.
OPTION 3: "Save to hard drive" "DV AVI" DVDA render 8.000 Mbps default bitrate
Peak Bitrate = 8097. Avg Bitrate = 6270.
Peak Q.Level = 12.75. Avg Q.Level = 5.42.
Okay, now do any of you experts want to comment? (I'm ready to learn something! You have a willing student!) Does anybody know what "Q.Level" is? I assume lower numbers are better, as Option 3 with the higher bit rate has a lower value.
Also, what does the "MP@ML" part of the stream description mean?
You guys doing pro or semi-pro work with the full Vegas -- what kind of bitrates do you find acceptable?
Oh, and no, I didn't burn all three to a dvd and watch it on a TV to see if I could tell the difference. That would be a sensible thing to do, but would take some more time. And I just spent a bunch of that time typing in this post.
One more thing: the Bitrate Viewer seemed just a little buggy. The number-of-frames count does not reset when you load a new file -- only resets to 0 when you first start the program. Load 3 files and number-of-frames is a cumulative count of all 3. Also, I got slightly different values when reloading the same file. Start the program, load the first file, get X results. Reload same file, get Y results (probably within 1% or so of X results). Reload same file 3rd, 4th time, etc., keep getting Y results. For my tests above, I shut down the program each time and used the first set of results for each file.
All comments welcome...
Tim L