Neil Paisnel wrote:
I have a question about this, that may help the OP too.,
Does iDVD take DVD size in to account with relation to sequence length and adjust the video quality to a level to fill the complete DL DVD.
iDVD will encode the source file to the correct codec for use on a DVD. It gets longer movies to fit on the disc by adjusting the bitrate of the DVD, so if the movie is longer, it will adjust the bitrate down to allow it to fit (make the file even smaller in size compared to the original) . A lower bitrate generally gives lower quality.
Having said that, the maximum normal bitrate for video on a DVD is around 9.8 Mbits - from:
https://documentation.apple.com/en/dvdstudiopro/usermanual/index.html#chapter=4% 26section=6%26tasks=true
"Bit rate directly determines file size, and thus how many minutes of material you can fit onto a DVD disc. SD-based DVD players support combined bit rates of up to 10.08 megabits per second (Mbps), but this must include the audio and subtitles as well. The maximum video bit rate is 9.8 Mbps."
The average bit rate, as opposed the the maximum bit rate, is about 4 Mbps. This is because some scenes are much simpler to compress, such as a static shot of a talking head, versus a very complex scene, such as an explosion. You won't need to be at the maximum bit rate all the time, which saves space on the disc.
Neil Paisnel wrote:
So would final DVD quality be better using a DL DVD for a one hour project than it would if it was squeezed on to a Single layer DVD?
No, it will never exceed the maximum video bit rate of 9.8 Mbps. To do so would create a non-standard disc and disc player problems - how would you know if any given DVD player would be able to support (keep up with) playing a higher than standard data rate?
If the encoded file does not fill the disc, then iDVD (or any DVD burning software) will write over the remaining space on the disc with essentially a "nothing to see here" file, so the player knows not to look for more content.
Note that the above is about a standard DVD and standard DVD player. It does not apply to a BluRay player which does read the file from the disc at a much higher bitrate.
MtD